Developing solid oxide electrolysis cells for CO₂ conversion: A critical power-to-X approach

Abstract

The substitution of traditional fossil fuels with renewable energy sources is a crucial endeavor for achieving carbon neutrality targets. However, the intermittency of solar, wind, and other renewables poses significant challenges to the power grid. Power-to-X (P2X) technologies play an essential role in enabling the efficient consumption of renewable energy. High-temperature solid oxide electrolysis cells (SOECs) to convert CO₂ offer a promising method for CO₂ conversion, allowing renewable electricity to be stored in chemical form and facilitating the resourceful utilization of carbon resources. In this paper, the mechanism of CO₂ reduction through SOECs is reviewed, two pathways for converting CO₂ to chemicals via SOECs are summarized, and the current markets and manufacturers of SOECs are elucidated. Based on this discussion and analysis, the main challenges and development directions for the large-scale application of SOECs in CO₂ conversion are further proposed.

Graphical abstract

Keywords

solid oxide electrolysis cells (SOECs) / CO₂ conversion / power-to-X (P2X)

1 Introduction

The excessive emissions of greenhouse gases are the primary drivers of global warming [1]. Climate change [2] has triggered glaciers melting [3] and ecosystem imbalances [4], seriously threatening the global economy and society. Adopted in 2015, the Paris Agreement established the objective of limiting the increase in global temperatures to within 2 °C above pre-industrial levels, while striving to further constrain it to 1.5 °C [5]. Under environmental pressure, the expansion of renewable energy sources (e.g., wind, solar) is actively underway [6,7]. Nevertheless, the inherent intermittency of renewable energy sources poses a barrier to their large-scale application [8].

Consequently, Power-to-X (P2X) technologies, where X represents CO, syngas, methanol, hydrocarbon, etc., have been developed as a means of converting electrical energy to chemical energy for storage [9,10]. Another advantage of P2X is its capability to employ captured carbon for the synthesis of chemicals, offering an ideal solution for carbon conversion [10]. Various catalysts such as metals, metal oxides, metal alloys, and metal-organic frameworks have been developed for electrochemical conversion of CO₂ [11].

At the core of P2X technologies are electrolysis cells, including polymer electrolyte membrane electrolysis cells (PEMECs) [12], alkaline electrolysis cells (AECs) [13], and solid oxide electrolysis cells (SOECs) [14,15]. Among these, SOECs have attracted increasing attention due to their favorable thermodynamic efficiencies, lack of reliance on precious metal catalysts, and high compatibility with downstream chemical processes (Fig.1) [16,17]. Compared to hydrogen production, employing SOECs to reduce CO₂ can decrease emissions while supplying carbon source for value-added utilization [9,15,16,18–21].

Although a substantial body of literature has reviewed CO₂ reduction via SOECs [9,15,16,18–21], fewer studies comprehensively examine the diverse conversion pathways for integrating renewable energy sources. Furthermore, a systematic review of the current market landscape, including an assessment of key manufacturers in the SOEC domain, has yet to be undertaken. Addressing these gaps is critical for advancing the understanding of the technical, economic, and scalability aspects of SOEC-based CO₂ utilization systems.

Herein, the mechanism of CO₂ reduction by SOECs is elucidated, three pathways for producing carbon-based chemicals via SOECs are analyzed, and key manufacturers of SOECs are explored. Finally, the challenges and future prospects are proposed to promote further development of these systems.

2 General description of SOECs

SOECs consist of solid oxide electrolytes and solid oxide electrodes. Based on the conductive properties of electrolytes, SOECs can be categorized into oxygen ion-conducting SOECs (O-SOECs) and proton-conducting SOECs (H-SOECs) (Fig.2(a) and Fig.2(b)).

2.1 O-SOECs

When O-SOECs are used for CO₂ conversion, CO₂ and/or H₂O receive electrons and decompose to produce oxygen ions at the cathode. Under the influence of an applied voltage, these oxygen ions migrate toward the anode, where they lose electrons to form oxygen or oxidize the substances introduced. Oxygen ions require high temperatures (typically above 600 °C) to achieve sufficient ionic conductivity (Fig.2(c)) [22]. Additionally, the transfer of oxygen ions across the electrode/electrolyte interface is generally slow, resulting in higher interfacial resistance. This necessitates high-temperature operation to maintain adequate performance. Although high temperatures help to overcome the activation energy barrier for oxygen ion migration and accelerate reaction rates, they also induce challenges such as catalyst agglomeration and carbon deposition, which adversely affect the long-term performance.

For O-SOECs, common electrolytes include zirconia-based electrolytes (e.g., yttria-stabilized zirconia, YSZ), ceria-based electrolytes (e.g., gadolinium-doped ceria, GDC), and perovskite oxides (e.g., lanthanum gallate doped with strontium and magnesium doped, LSGM) [10,16]. Zirconia-based electrolytes exhibit superior stability under high-temperature conditions (800‒1000 °C), whereas ceria-based electrolytes and perovskite oxides demonstrate enhanced conductivity around 600‒800 °C.

In O-SOECs, catalyst agglomeration and carbon deposition at the cathode are major challenges due to high operation temperature, which can severely degrade performance and shorten service life. To overcome these issues, researchers have explored innovative strategies. For instance, numerous perovskite oxides have been developed as catalysts, owing to their excellent structural stability under high temperatures and CO₂-rich environments [16].

To further enhance the catalytic performance, perovskite oxides can undergo an exsolution treatment, is a process in which active metal nanoparticles, originally dissolved as cations within the host oxide lattice, are induced to migrate to the surface under reducing conditions. This results in the formation of finely dispersed, strongly anchored metal nanoparticles on the oxide surface, significantly reducing the risk of particle agglomeration or sintering at high temperatures [23]. Besides, perovskite oxides can be easily modified through exsolution to adjust the concentration of oxygen vacancies, which play a crucial role in CO₂ adsorption and activation, thereby improving the catalytic activity [24].

As discussed in Section 3, exsolution has emerged as a hot research topic in recent years, with many researchers developing a series of high-performance catalysts based on this strategy.

2.2 H-SOECs

As for H-SOECs, hydrogen sources release electrons and generate protons at the anode. These protons then migrate to the cathode, where they reduce CO₂ and/or other substances under the influence of applied voltage. Protons, being lighter and requiring less activation energy for transport, enable high ionic conductivity at reduced operating temperatures, typically in the range of 400‒600 °C. Additionally, their extraordinary mobility contributes to more efficient charge transfer at the interface, leading to lower interfacial resistance and thereby improving overall electrochemical performance while decreasing operating temperatures (Fig.2(d)) [22].

Excellent electrochemical performance in H-SOECs corresponds to high current densities. In processes such as CO₂ hydrogenation, protons directly participate in the reaction, which can lower overpotentials and facilitate the formation of products such as methane. Moreover, operating at reduced temperatures decreases energy consumption, minimizes thermal stress, and enhances long-term stability. Electrolytes for H-SOECs are typically ABO₃ perovskite oxides, where A = Ca, Sr, Ba, etc., and B = Zr, Ce, etc.) [10,16].

Recent studies have underscored that one of the major challenges for H-SOECs is the degradation of proton-conducting electrolytes in CO₂-rich environments [22]. This degradation is primarily caused by the formation of carbonates and other substances at the electrolyte surface, which hinder proton conduction and ultimately reduce cell efficiency and durability. To address these issues, researchers have been actively exploring mitigation strategies, including advanced electrolyte composition, surface coatings, and protective layers.

For instance, the chemical stability of BaCeO₃-based oxides has attracted widespread attention. It has been shown that BaCeO₃ perovskite oxides readily react with H₂O and CO₂ at operating temperatures, forming Ba(OH)₂ and BaCO₃ [25]. Medvedev et al. [26] investigated the effect of Zr doping on the stability of BaCeO₃ and found that the Gibbs free energy for the reaction between BaCe_1−xZr_xO₃ and H₂O/CO₂ increases with Zr content at the same temperature. This indicates that Zr doping can enhance the chemical stability of BaCeO₃.

Other studies have demonstrated that substituting Ce with Dy and Nb in Ba (Ce, Zr)O₃ can further mitigate undesirable reactions in CO₂-rich atmosphere, thereby enhancing the material’s chemical stability. Danilov et al. [27] treated BaCe_0.8−xZr_xDy_0.2O_3−δ (x = 0.2 ‒ 0.6) samples in CO₂ environments and observed that higher Zr content led to improved chemical stability, similar to the trend seen in BaCe_1−xZr_xO₃. Nb-doped Ba(Ce, Zr)O₃ compounds have also been thoroughly examined. The findings indicate that incorporating more than 10% Zr and 10% Nb is crucial for achieving bulk chemical stability [28].

In addition to material doping, applying protective coatings is another effective strategy for extending the service life of H-SOECs. Zhou et al. [29] integrated Fe₂O₃ functional layer with a single cell to form an H-SOEC. At 1.3 V and 700 °C, the reactor delivered an electrolysis current density of 1698 mA/cm². Moreover, it demonstrated stable operation for 630 h at 650 °C under both constant-potential and constant-current electrolysis modes.

3 Pathways of CO₂ conversion to chemicals using SOECs

In this paper, the processes of CO₂ conversion using SOECs are classified into two main categories:

CO₂ reduction via SOECs without additional steps: This process mainly includes five types of reactions, CO₂ direct reduction to produce CO; co-electrolysis of CO₂ and H₂O to produce syngas; dry reforming of methane (DRM) to produce syngas and CO; CO₂ hydrogenation to produce methane; and oxidation of methane/ethane via CO₂ to produce ethylene.

Coupling co-electrolysis with other processes: These processed can be further divided into three types: Co-electrolysis for preparing methane; co-electrolysis for preparing methanol; and co-electrolysis for Fischer-Tropsch synthesis (F-T synthesis) (Fig.2(e)).

3.1 CO₂ reduction via SOECs without other steps

SOECs enable the direct reduction of CO₂ into valuable products through a simplified process with low equipment requirements, making them a favorable option for CO₂ conversion.

3.1.1 CO₂ direct reduction

The direct reduction of CO₂ allows for power-to-CO, with O-SOECs being the only viable option in this context. However, stability issues arise in traditional Ni-based cathodes due to Ni agglomeration, migration, and carbon deposition. To address this, nonstoichiometric mixed ionic and electronic conducting oxide electrocatalysts have been synthesized [30]. Examples include Sr₂Fe_1.5−xZr_xMo_0.5O_6−δ (Fig.2(f)) [31] and Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3−δ [32], which are promising alternatives.

While perovskite oxides offer stability, their electrocatalytic activity still requires further improvement. Over the past three years, the exsolution of metal nanoparticles from the surface of perovskite oxides has gained significant attention. Zhao et al. [33] proposed a dual-exsolution approach on a self-assembled cathode. In this method, Ni nanoparticles are in situ exsolved on Ni doped Sr₂Fe_1.5Mo_0.5O_6−δ and Ni doped Gd_0.1Ce_0.9O_2−δ composite surface, resulting in a current density of 1.72 A/cm² at 1.5 V and 800 °C, with durability demonstrated over 100 h.

Yang et al. [34] reported a novel high-entropy cathode, Pr_0.8Sr_1.2(CuFe)_0.4Mo_0.2Mn_0.2Nb_0.2O_4−δ, which incorporates uniformly in situ exsolved CuFe@FeO_x nanoparticles. Single cells with this cathode exhibited a consistently high current density of 1.95 A/cm at 1.5 V and 800 °C (Fig.3(a)).

Additionally, Lee et al. [35] designed a hybrid nanofiber electrode, La_0.6Sr_0.4Co_0.15Fe_0.8Pd_0.05O_3−δ, in which in situ exsolved Co nanoparticles enhance CO₂ adsorption on the surface. SOECs using this electrode yield a current density of 2.2 A/cm² at 1.5 V and 800 °C (Fig.3(b)). Barnett et al. [36] reported a composite cathode by combining Sr_0.95Ti_0.3(Fe_0.9Ru_0.1)_0.7O_3−δ and Sr₂Fe_1.5Mo_0.5O_6−δ, where in situ exsolved FeRu nanoparticles exhibited excellent electrocatalytic performance. At 1.3 V and 800 °C, the current density exceeds 2.15 A/cm².

Despite advancements in optimizing cathode electrocatalysts, the oxygen evolution reaction (OER) at the anode still suffers from sluggish kinetics due to the four-electron process involved. To address this challenge, extensive research has been devoted to developing advanced anode materials and employing innovative surface modification strategies.

For instance, Liu et al. [37] developed a series of PrBaCo_2−xFe_xO_5+δ perovskites with tailored ion orderings. Both experimental analyses and density functional theory calculations demonstrated that A-site cation ordering significantly enhances oxygen bulk migration, surface transport capacities, and OER activities, while the ordering of oxygen vacancies negatively affects these properties. Li et al. [38] replaced Ba in Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3−δwith lanthanides to create Ln_0.5Sr_0.5Co_0.8Fe_0.2O_3−δ (LnSCF, where Ln = La, Pr, Nd, Sm) to regulate material stability and performance. The incorporation of La and Pr was enhanced stability by suppressing surface segregation while maintaining high OER activity. As a result, SOECs utilizing La_0.5Sr_0.5Co_0.8Fe_0.2O_3−δ anodes achieved an optimal current density of 1.69 A/cm² at 1.6 V, with excellent stability for CO₂ electrolysis at 800 °C.

Furthermore, Yang et al. [39] discovered that co-synthesizing La_0.6Sr_0.4Co_0.8Fe_0.2O_3−δ with 40 wt% (mass fraction) GDC improved conductivity, oxygen exchange kinetics, and bulk diffusion. This optimized electrode achieved an impressive CO₂ electrolysis current density of 2.6 A/cm² at 1.6 V and 800 °C when implemented in a Ni-YSZ supported cell. Yang et al. [40] found that Ba_0.95La_0.05FeO_3−δ exhibited excellent OER performance due to its low oxygen vacancy formation energies and favorable oxygen adsorption properties on its surfaces. Under an applied electrolysis voltage of 1.5 V at 850 °C, the current density reached 1.53 A/cm² in a 50% H₂-50% CO₂ atmosphere.

However, from an economic perspective, CO is inexpensive, while O₂ has limited commercial value. As a result, researchers often employ co-electrolysis of CO₂ and H₂O to produce syngas, thus increasing the value of the products. Alternatively, coupling oxidation reaction of other substances at the anode can further boost kinetic performance.

3.1.2 Co-electrolysis of CO₂ and H₂O

Co-electrolysis of CO₂ and H₂O enables power-to-syngas, a process that can mitigate the degradation of cathode catalysts, particularly Ni-based catalysts, by reducing carbon deposition and optimizing electrochemical reactions. Moreover, the products from this reaction, such as methane, methanol, and fuels, can be further utilized to produce valuable chemicals. As a result, co-electrolysis has become a significant area of research.

In the field of O-SOECs, Wu et al. [41] improved cathode electrocatalysts by creating in situ exsolved heterostructural Cu/Fe₃O₄ nanoparticles on the parent CuFe₂O₄ surface. This heterostructure has great electrocatalytic activity and maintains the activation of nanoparticles. Their findings demonstrated that the designed SOEC could operate stably over long-term high-voltage operation with an outstanding Faradaic efficiency of nearly 100%. In another study, Wu et al. [42] highlighted the efficient electrocatalytic activity of La_0.6S_r0.4Fe_0.8Mn_0.2O₃. Importantly, the ratio of CO and H₂ could be directly controlled by adjusting the CO₂ and H₂O flow rate ratio. This was attributed to the formation of bicarbonate species on the catalyst surface, which facilitated CO₂ reduction and suppressed the water-gas shift reaction (Fig.4(a)).

Based on these findings, Zhang et al. [43] investigated the impact of Mn doping on La_0.3Ca_0.6Ni_0.05Ti_0.95O_3−γ. The results demonstrated that 5% Mn enhanced the in situ exsolution process, boosting electrical conductivity. At 1.8 V and 900 °C, the current density reached 2.89 A/cm², with no degradation observed after 133 h of high-temperature operation. Additionally, Barnett et al. [36] developed a composite cathode combining Sr_0.95Ti_0.3(Fe_0.9Ru_0.1)_0.7O_3−δ and Sr₂Fe_1.5Mo_0.5O_6−δ, with in situ exsolved FeRu nanoparticles. This composite cathode exhibited excellent selectivity for co-electrolysis, with CO content in products exceeding 50% at 800 °C and different current densities (Fig.4(b)).

Hou et al. [16] provided a comprehensive review of the development of H-SOECs for co-electrolysis. Despite their potential, H-SOECs have received limited for syngas production due to their complex fabrication process. For instance, Bausá et al. [44] used a composite cathode made of La_0.8Sr_0.2MnO_3−δ and BaCe_0.2Zr_0.7Y_0.1O_3−δ, activated by Pr₆O₁₁-CeO₂ nanoparticles. Their study demonstrated that H₂ and CO were produced at rates of 3.71 and 0.40 mL/min, respectively, at a current density of 0.104 A/cm².

Among CO₂ conversion technologies, co-electrolysis has significant potential due to its high efficiency and compatibility. Future trends will focus on improving cathode catalysts performance, achieving precise control over the syngas ratio, expanding syngas production, and reducing costs [45].

3.1.3 DRM

DRM allows for power-to-syngas and CO production. Biogases generally consist of 60% to 70% methane, 30% to 40% CO₂, and trace impurities such as H₂S and H₂O. DRM drives the conversion of biogas to syngas, highlighting its potential as an alternative to fossil fuels. In the context of SOECs, DRM involves the coupling of methane partial oxidation at the anode to produce syngas, while simultaneously facilitating CO₂ electrolysis.

DRM has mostly been explored in O-SOECs. Liu et al. [46] designed a Ni-Gd_0.1Ce_0.9O₂ porous cathode and a Ni-Y_0.16Zr_0.84O_1.92 microchannel anode for CO₂ electrolysis and methane oxidation. The SOEC with this anode showed durability for 400 h at 800 °C, with current density of 2 A/cm². Dong et al. [47] prepared in situ exsolved Fe nanoparticles on (La_0.75Sr_0.25)_0.9Cr_0.5Mn_0.5O_3−δ, constructing an active metal-oxide interface. The Fe nanoparticles provided active sites for methane oxidation, enhancing coking resistance and catalyst stability. The SOEC demonstrated stable performance at 850 °C for 70 h without significant degradation.

Notably, Song et al. [48] made major breakthroughs in this area. By calcinating physical mixtures of anode powder (La_0.6Sr_0.4Co_0.2Fe_0.8O_3−δ-Ce_0.8Sm_0.2O_2−δ) and commercial RuO₂ powder in static air at high temperatures, they anchored Ru on the inner surface of the porous anode. This approach resulted in better DRM activity (90% selectivity) and enhanced durability (300 h), outperforming materials obtained through infiltration and doping methods (Fig.4(c)). In another study, Guo et al. [49] reported outstanding DRM performance by producing in situ exsolved CoFe nanoparticles on the La_0.6Sr_0.4Ti_0.3Fe_0.5Co_0.2O_3−δ anode surface. The methane conversion reached 86.9%, with CO selectivity of 90.1% at 800 °C. Additionally, the SOEC with this anode operated stably for over 1250 h (Fig.4(d)).

These studies highlight the dual benefit of DRM in SOECs, where methane is converted to syngas at the anode, and CO₂ is reduced to CO at the cathode, enabling the utilization of greenhouse gases while simultaneously storing renewable electricity in chemicals. Given these advantages, DRM is considered as a promising direction and is anticipated to be a key pathway for P2X technologies in the future.

3.1.4 CO₂ hydrogenation

CO₂ hydrogenation allows for power-to-methane. In O-SOECs, when suitable catalysts are present, the syngas generated at the cathode can undergo methanation reaction (MR), essentially in situ F-T synthesis. Early studies have shown that MR is an exothermic reaction, typically requiring temperatures around 350 °C. However, O-SOECs operate at temperatures above 600 °C, creating a temperature gap between co-electrolysis and MR [50]. Although tubular SOECs with established temperature gradients have been reported, the methane yield remains low [51,52]. To address this, Błaszczak et al. [53] employed the impregnation method to disperse Co metal particles on the surface of Ni-YSZ. Their results demonstrated that the methane concentration in the outlet stream of the cathode, when containing 3.6 wt% Co, was 2.5 times higher than that of the original sample.

In H-SOECs, CO₂ hydrogenation involves coupling the oxidation reaction of hydrogen sources (e.g. H₂O, H₂, etc.) at the anode to assist the reduction of CO₂ at the cathode. H-SOECs are particularly advantageous for power-to-methane due to their ability to operate at lower temperatures and directly reduce CO₂ to methane. Duan et al. [54] developed a reversible H-SOC, utilizing H₂O as the hydrogen source for methane production. In electrolysis mode, methane yield was negatively correlated with temperature. At 500 °C and an electrolysis current of −1.625 A, the methane yield reached 7.5%. Li et al. [55] used proton ceramic membranes as hydrogen pumps and Ir-Ce-based oxides as catalysts. By controlling the species of Ir, they tuned Ir-O hybridization and altered the chemical environment of the catalyst surface, stabilizing a specific transition state. It resulted in near 100% methane selectivity when H₂ was used as the hydrogen source.

Furthermore, Pan et al. [56] harnessed the unique properties of protonic ceramic electrolysis cells (PCECs) to accomplish co-electrolysis of CO₂ and H₂O. At an electrolysis current of −1 A/cm², the methane yield reached 34.6%. Ye et al. [57] selectively impregnated a thin CeO₂ layer onto the surface of BaCe_0.7Zr_0.1Y_0.1Yb_0.1O_3−δ, resulting in a PCEC that exhibited more than a threefold increase in methane selectivity at 550 °C and 1250 mA/cm² compared to a cell using a pristine electrode (Fig.5(a) and Fig.5(b)).

Compared to the three conversion processes mentioned above, literature on CO₂ hydrogenation is scarce. This is partly due to the fact that methane is both a greenhouse gas and naturally abundant, resulting in a relatively low market value. As a result, researchers are increasingly interested in coupling the oxidation reactions of other substances at the anode to produce higher-value chemicals.

3.1.5 Oxidation of methane/ethane via CO₂ to produce ethylene

Oxidation of methane/ethane via CO₂ enables power-to-ethylene conversion. Ethylene is a fundamental raw material in the petrochemical industry and serves as a precursor for various bulk chemicals, including polyethylene, ethylene oxide, and ethylene glycol. Currently, ethylene is mainly produced from non-renewable resources such as petroleum and coal. In contrast to non-oxidative processes, the oxidative coupling of methane (OCM) and the oxidative dehydrogenation of ethane (ODE) are thermodynamically advantageous. Therefore, partial oxidation of methane and ethane to ethylene is coupled at the anode, aiming to produce ethylene [58–60].

For O-SOECs, Ye et al. [61] focused on OCM. Single-crystalline Ni nanoparticles were exsolved in porous single-crystalline CeO₂ monoliths, allowing for electrochemical regulation of the chemical states and flux of active oxygen species at the anode. The results demonstrated an unprecedented C₂ selectivity (ethane and ethylene) of over 99.5%, with a methane conversion rate of approximately 7%. Additionally, the SOEC with this anode could operate continuously for over 100 h (Fig.5(c) and Fig.5(d)) [61]. ODE has also been explored at the anodes of O-SOECs. Sun et al. [62] fabricated an SOEC using Sr₂Ti_0.8Co_0.6Fe_0.6O_6−δ as the electrode material, achieving an ethylene yield of 66.3% at 800 °C, which is among the highest values reported in the literature. Furthermore, He et al. [63] constructed a metal-oxide interface, Co@CeO₂, through in situ exsolution, which achieved an ethane conversion rate of 33.1% and an ethylene selectivity of 88.9% at 1.0 V.

Besides, Qin et al. [64] prepared CoFe@Sr_1.95Fe_1.4Co_0.1Mo_0.5O_6‒δ nanoalloy-oxide heterostructure via in situ exsolved process. At 800 °C and 1.6 V, the ethane conversion rate exceeded 36.4% and ethylene selectivity was over 94.5%. After 50 h of testing, the degradation of the SOEC was negligible (Fig.6(a)). In another study, Zhang et al. [65] fabricated an ODE anode electrocatalyst, Ce_0.6Mn_0.3Fe_0.1O_2−δ-NiFe-MnO_x, via a self-assembly process. At 1.8 V at 700 °C, the ethane conversions rate exceeded 52.23%, with 94.11% ethylene selectivity.

Studies on H-SOECs for OCM and ODE is still limited. Zhang et al. [66] achieved the ODE reaction at 700 °C in H-SOECs, where Ni_xCu_1‒x nanoparticles were exsolved on the Nb_1.33(Ti_0.8Mn_0.2)_0.67O_4−δ surface to form a metal-oxide interface. The ethane conversion rate reached 75.2%, with an ethylene selectivity of nearly 100% at 700 °C (Fig.6(b) and Fig.6(c)).

Overall, research on the partial oxidation of alkanes coupled CO₂ reduction at the anodes is still in its infancy. The optimum reaction conditions require further exploration, and the mechanisms to prevent the deep oxidation of alkanes need additional investigation.

3.2 Coupling co-electrolysis with other processes

Coupling co-electrolysis using SOECs with other processes, especially exothermic reactions, can improve the energy efficiency and reduce operating costs while enabling the production of different kinds of chemicals.

3.2.1 Co-electrolysis for preparing methane

The coupling of co-electrolysis and MR allows for power-to-methane production through three main approaches: designing SOECs and MR separately; integrating SOECs with MR; and in situ F-T synthesis on the anode of SOECs, as partially introduced Section 3.1.4. Additionally, methane can be produced using specially engineered SOECs that incorporate catalysts with high methane selectivity, operate under pressurized, low-temperature conditions, and include hydrogen addition. Typically, elevated pressure and reduced temperature favor methane production. By pressurizing the methanation reaction during the co-electrolysis phase, synthetic natural gas composed of nearly 100% methane can be obtained. However, this approach tends to decrease overall production efficiency and increase costs [16].

Due to the significant limitations of the first two methods (e.g., high costs, substantial heat losses), related studies are relatively scarce. For instance, Wang et al. [67] developed an integrated hybrid reactor model that combined a tubular SOEC electrolysis cell with the F-T process. In this setup, feed gas was co-electrolyzed to produce a specific proportion of syngas, which was then converted into methane via methane steam reforming within the F-T process. Their study examined the effect of co-electrolysis, methane water-vapor reforming, and the reverse water-gas shift reaction on the power-to-methanation pathway. The simulation results helped optimize various reactor parameters, such as temperature, voltage, and pressure, that directly impact energy consumption, production yield, and overall system stability.

3.2.2 Co-electrolysis for preparing methanol

The coupling of co-electrolysis with the methanol production process allows for power-to-methanol conversion. Currently, the production of methanol from syngas has been successfully commercialized. Co-electrolysis of H₂O and CO₂ to produce syngas, followed by methanol synthesis, is considered an environmental friendliness approach. Al-Kalbani et al. [68] compared two CO₂-to-methanol conversion methods, CO₂ hydrogenation and high-temperature co-electrolysis, using Aspen HYSYS modeling. The results reveal that the CO₂ electrolysis method achieves an energy efficiency of 41%, nearly twice that of the CO₂ hydrogenation process.

However, due to the high cost of SOECs, implementing this method at an industrial scale is currently economically unfeasible. Zong et al. [69] assessed nine pathways for producing methanol from CO_2, revealing that although co-electrolysis has the lowest carbon footprint (0.28 t CO₂ eq/t methanol), the levelized cost of methane is extremely high ($590.3/t methanol).

However, some scholars are optimistic about this technology. Ferguson et al. [70] predicted that by 2030, the capital cost of SOECs will be reduced by 50%, making power-to-methanol more cost-effective than power-to-methane. Zhang and Desideri [71] explored large-scale power-to-methanol conversion using SOEC co-electrolysis combined with methanol synthesis. Their system demonstrated a strong balance between methanol production cost and energy efficiency, achieving energy and carbon conversion efficiencies of 72% and 93.6%, respectively, while annually consuming 146.7 kt of CO₂. Khan et al. [72] examined a solar-integrated process that co-electrolyzed H₂O and CO₂ using SOECs to generate hydrogen-rich syngas, which was subsequently directed to methanol synthesis via a network of heat exchangers and compressors. This system achieved a solar-to-fuel conversion efficiency of 29.1%, producing methanol at a rate of 41.5 kg per hour, along with 199 kW of thermal power and 501 kW of electrical power. The levelized fuel cost was found to be $430/t methanol.

3.2.3 Co-electrolysis for F-T synthesis

Co-electrolysis for F-T synthesis enables power-to-fuel conversion, providing a pathway to produce a range of alkanes, from light gases to heavy waxes. These alkanes could serve as alternatives to oil, helping to mitigate energy, economic, and political crises caused by petroleum shortages. Therefore, co-electrolysis for F-T synthesis has garnered extensive attention.

For instance, Zang et al. [73] developed a comprehensive techno-economic model to assess the feasibility of this process. The study highlights the importance of managing heating costs and proposes alternative system layouts that maximize thermal and chemical energy utilization. Additionally, given the degradation of the SOEC stacks over time, the model suggested that operating at a current density of 500 mA/cm² was more cost-effective in the long run compared to 850 mA/cm². Pratschner et al. [74] evaluate off-grid and grid-based scenarios of three process configurations, concluding that scaling up the plant showed diminishing returns in net production costs after surpassing a 100 MW threshold. Therefore, future power-to-fuel projects are expected to be designed at a 100 MW scale.

In summary, while the CO₂ conversion technologies discussed in Section 3.2 remain at the theoretical research stage and are not yet ready for industrial application, the methods covered in Section 3.1, particularly CO direct reduction and co-electrolysis of CO₂ and H₂O, are the two most extensively studied. Compared with CO₂ direct reduction, co-electrolysis of CO₂ and H₂O not only produces higher-value synthesis gas but also exhibits superior reaction kinetics. Furthermore, recent research has also focused on utilizing SOECs for DRM, CO₂ hydrogenation, and the oxidation of methane/ethane via CO₂ to produce ethylene. These methods are particularly promising because they enable the conversion of greenhouse gases (CO₂ and methane) into valuable products like syngas and ethylene, while CO₂ hydrogenation remains relatively underexplored due to the low value of its products, these approaches are seen as critical directions for future development.

4 Markets and manufacturers of SOECs

Over the past few decades, substantial investments have been made globally in the research and commercialization of CO₂ conversion using SOECs [75]. Initially, the development of SOECs was emphasized in the United States and European countries, where a number of companies focused on specialized fields of this technology. In the United States, Bloom Energy pays attention to the implementation of co-electrolysis for syngas production and DRM using SOECs. In Europe, the German company Sunfire is committed to the industrial-scale preparation of syngas. Denmark’s Haldor Tøpsoe intends to integrate SOECs with CO₂ capture and conversion technologies to develop an efficient carbon-neutral production chain. Meanwhile, the UK-based Ceres Power has leveraged its solid oxide fuel cells (SOFCs) technology platform to actively advance the application of SOECs in co-electrolysis for syngas production.

In recent years, Asian countries have increasingly recognized the importance of SOECs in achieving carbon neutrality goals, resulting in greater investment in this technology. In Japan, Tosoh with its long-term technological accumulation in materials science, especially in ceramics, has made rapid progress in SOECs for syngas production. LG Fuel Cell Systems in the Republic of Korea, mainly focus on SOFCs but is also exploring SOEC applications. Notably, in China, several companies are growing rapidly in the SOEC field. Ningbo SOFCMAN offers multiple key materials, components (e.g., catalyst powders, etc.) and test equipment for SOEC research. Chao Zhou Three-Circle, a leading manufacturer of electronic ceramic components, specializes in the design and manufacture of SOFCs and has recently optimized the cell and stack designs for SOECs. A summary of the key SOEC manufacturers is presented in Tab.1.

It is notable that while the market for SOECs is growing, it remains at a nascent stage compared with AECs and PEMECs. According to Precedence Research, the global electrolyzer market was valued at 12.81 billion USD in 2023 and is expected to exceed 278.82 billion USD by 2033, reflecting a compound annual growth rate of 36% from 2024 to 2033 (Fig.7(a)). Nonetheless, in 2023, SOECs accounted for only 2.17% of this total market share, with most of their applications focused on hydrogen production (Fig.7(b)) [76].

Geographically, North America currently dominates the electrolyzer market, driven by high demand in manufacturing processes and extensive hydrogen use in the power sector. The region’s well-established manufacturing infrastructure has been a key factor in this growth. In Europe, substantial investments from leading market players and a strong infrastructure presence have contributed to significant revenue generation. Meanwhile, the Asia Pacific region is experiencing increased demand for clean energy and fuel, further spurring hydrogen demand (Fig.7(c)) [76]. Consequently, the Asia Pacific electrolyzer market was valued at $ 5.84 billion in 2023 and is projected to grow to approximately $ 138.95 billion by 2033, with a compound annual growth rate of 37% from 2024 to 2033 (Fig.7(d)) [76].

Policy incentives play a pivotal role in driving the market growth of SOECs and other electrolyzer technologies. By May 2024, carbon neutrality targets had been established by 151 countries, with 120 of these countries having formalized commitments through legislation or policy measures [77]. Regulatory frameworks that mandate or incentivize the use of renewable energy and low-carbon technologies, such as the US Inflation Reduction Act, the European Green Deal, and similar initiatives in the Asia Pacific, have been created to stimulate demand for electrolyzers [77]. These frameworks also help build long-term market confidence, which is crucial for sustained growth. Moreover, government-led policies that promote collaborative research between academia and industry can lead to breakthroughs in efficiency and durability of SOECs, further enhancing their market potential. Particularly, as a special incentive, carbon pricing mechanisms impose costs on CO₂ emissions, making carbon-intensive processes less economically viable. This shift in cost structures improves the competitiveness of low-carbon technologies like SOECs and other electrolyzers, as their operational costs become comparatively lower than those of conventional fossil fuel-based systems.

5 Conclusions and perspectives

As advancements in SOECs continue, this technology holds significant promise for the efficient electrochemical conversion of CO₂ into value-added chemicals and fuels. Key advantages, such as high energy efficiency, the absence of precious metal catalysts, and strong compatibility with high-temperature industrial processes, distinguish SOECs from conventional systems like AECs and PEMECs.

In view of global carbon neutrality targets, it is increasingly recognized that integrating CO₂ conversion technologies, exemplified by SOECs, with carbon capture and storage infrastructure will be critical for achieving deep decarbonization. This integration not only facilitates carbon mitigation but also enables the valorization of captured CO₂, thereby contributing to the development of a circular carbon economy [78–86].

Nevertheless, several challenges must be addressed before large-scale implementation of SOECs. These include material degradation during prolonged high-temperature operation, high capital investment, and limited demonstration at industrial scales. Overcoming these barriers will require sustained research efforts, technological innovation, and system-level integration to fully unlock the potential of SOECs in future low-carbon energy systems.

First, the high-temperature operation of SOECs poses significant challenges to the long-term stability of electrolyte materials. Degradation mechanisms such as thermal expansion mismatch and interfacial reactions can lead to performance loss or mechanical failure over time. Although promising electrolyte materials like YSZ and GDC have been developed, their durability in large-scale stacks under industrial conditions requires further validation. To address this, advanced characterization techniques, such as in situ diffuse reflectance infrared Fourier transform spectroscopy, in situ X-ray photoelectron spectroscopy, and X-ray absorption near-edge structure, can be employed to investigate electrode processes.

Second, the economic barrier remains a significant obstacle to SOEC commercialization. The high capital cost arises from expensive materials and complex system design, while elevated operating temperatures further increase energy demands. Reducing investment through mass production, process simplification, and the use of cheaper materials is crucial. The current objective is to achieve a cost of $1140/kW by 2030 and $600/kW by 2050. Additionally, the integration of renewable electricity and industrial waste heat can help reduce operational costs and improve economic feasibility.

Finally, integrating SOEC co-electrolysis with downstream fuel and chemical synthesis holds great potential for carbon neutrality. The ability to produce syngas directly from CO₂ and H₂O makes SOECs ideal for coupling with industrial processes. However, most current research remains at the theoretical or laboratory scale, with few demonstrations under industrial conditions. Bridging this gap will require more pilot-scale studies, system integration, and interdisciplinary collaboration to advance industrial deployment.

References

[1] Allen M R, Frame D J, Friedlingstein P. . Geological Net Zero and the need for disaggregated accounting for carbon sinks. Nature, 2025, early access

[2] Rogger J, Judd E J, Mills B J W. . Biogeographic climate sensitivity controls Earth system response to large igneous province carbon degassing. Science, 2024, 385(6709): 661–666

[3] An Z, Zhou W, Zhang Z. . Mid-pleistocene climate transition triggered by Antarctic Ice Sheet growth. Science, 2024, 385(6708): 560–565

[4] Lachs L, Bozec Y M, Bythell J C. . Natural selection could determine whether Acropora corals persist under expected climate change. Science, 2024, 386(6727): 1289–1294

[5] Schleussner C F, Ganti G, Lejeune Q. . Overconfidence in climate overshoot. Nature, 2024, 634(8033): 366–373

[6] Walmsley T G, Philipp M, Picón-Núñez M. . Hybrid renewable energy utility systems for industrial sites: A review. Renewable & Sustainable Energy Reviews, 2023, 188: 113802

[7] Wen Z, Yao L, Cheng F. . A comprehensive review of wind power based power system frequency regulation. Frontiers in Energy, 2023, 17(5): 611–634

[8] Xu Y, Du Y, Chen H. . Recent advances in rational design for high-performance potassium-ion batteries. Chemical Society Reviews, 2024, 53(13): 7202–7298

[9] Kang H, Ma J, Perathoner S. . Understanding the complexity in bridging thermal and electrocatalytic methanation of CO₂. Chemical Society Reviews, 2023, 52(11): 3627–3662

[10] Jang I, SA Carneiro J, Crawford J O. . Electrocatalysis in solid oxide fuel cells and electrolyzers. Chemical Reviews, 2024, 124(13): 8233–8306

[11] Ashraf S, Gohar O, Khan M Z. . Exploring the frontiers of electrochemical CO₂ conversion: A comprehensive review. Nano Materials Science, 2024,

[12] Liu R T, Xu Z L, Li F M. . Recent advances in proton exchange membrane water electrolysis. Chemical Society Reviews, 2023, 52(16): 5652–5683

[13] Wan L, Xu Z, Xu Q. . Key components and design strategy of the membrane electrode assembly for alkaline water electrolysis. Energy & Environmental Science, 2023, 16(4): 1384–1430

[14] Cao J, Hu Y, Zheng Y. . Recent advances and challenges of nitrogen/nitrate electro catalytic reduction to ammonia synthesis. Frontiers in Energy, 2024, 18(2): 128–140

[15] Kang S, Pan Z, Guo J. . Scientometric analysis of research trends on solid oxide electrolysis cells for green hydrogen and syngas production. Frontiers in Energy, 2024, 18(5): 583–611

[16] Hou X, Jiang Y, Wei K. . Syngas production from CO₂ and H₂O via solid-oxide electrolyzer cells: Fundamentals, materials, degradation, operating conditions, and applications. Chemical Reviews, 2024, 124(8): 5119–5166

[17] Liu H, Yu M, Tong X. . High temperature solid oxide electrolysis for green hydrogen production. Chemical Reviews, 2024, 124(18): 10509–10576

[18] Zheng Y, Chen Z, Zhang J. Solid oxide electrolysis of H₂O and CO₂ to produce hydrogen and low-carbon fuels. Electrochemical Energy Reviews, 2021, 4(3): 508–517

[19] Tezel E, Whitten A, Yarema G. . Electrochemical reduction of CO₂ using solid oxide electrolysis cells: Insights into catalysis by nonstoichiometric mixed metal oxides. ACS Catalysis, 2022, 12(18): 11456–11471

[20] Zong S, Zhao X, Jewell L L. . Advances and challenges with SOEC high temperature co-electrolysis of CO₂/H₂O: Materials development and technological design. Carbon Capture Science & Technology, 2024, 12: 100234

[21] Xu R, Liu S, Yang M. . Advancements and prospects of perovskite-based fuel electrodes in solid oxide cells for CO₂ electrolysis to CO. Chemical Science, 2024, 15(29): 11166–11187

[22] Malavasi L, Fisher C A, Islam M S. Oxide-ion and proton conducting electrolyte materials for clean energy applications: Structural and mechanistic feature. Chemical Society Reviews, 2010, 39(11): 4370–4387

[23] Luo Y, Zhang D, Liu T. . In situ exsolution of quaternary alloy nanoparticles for CO₂‒CO mutual conversion using reversible solid oxide cell. Advanced Functional Materials, 2024, 34(40): 2403922

[24] Du Y, Zhao L, Xiao Y. . High electrolysis performance of the SOEC cathode by creating oxygen vacancies to regulate the adsorption energy. Journal of Materials Chemistry. A, Materials for Energy and Sustainability, 2024, 12(42): 28911–28918

[25] Jing J, Pang J, Chen L. . Structure, synthesis, properties and solid oxide electrolysis cells application of Ba(Ce, Zr)O₃ based proton conducting materials. Chemical Engineering Journal, 2022, 429: 132314

[26] Medvedev D, Lyagaeva J, Plaksin S. . Sulfur and carbon tolerance of BaCeO₃-BaZrO₃ proton-conducting materials. Journal of Power Sources, 2015, 273: 716–723

[27] Danilov N A, Lyagaeva J G, Medvedev D A. . Transport properties of highly dense proton-conducting BaCe_0.8–xZr_xDy_0.2O_3–δ materials in low- and high-temperature ranges. Electrochimica Acta, 2018, 284: 551–559

[28] Gore C M, White J O, Wachsman E D. . Effect of composition and microstructure on electrical properties and CO₂ stability of donor-doped, proton conducting BaCe_1‒(x+y)Zr_xNb_yO₃. Journal of Materials Chemistry. A, Materials for Energy and Sustainability, 2014, 2(7): 2363–2373

[29] Zhang Y, Song R, Zou J. . Research on CO₂ reduction reaction in the proton conducting solid oxide electrolysis reactor with Fe catalyst layer coverage. International Journal of Hydrogen Energy, 2025, 98: 86–95

[30] Hanif M B, Rauf S, Khan M Z. . Innovative advances and challenges in solid oxide electrolysis cells: Exploring surface segregation dynamics in perovskite electrodes. Materials Science and Engineering R Reports, 2024, 161: 100864

[31] Zhang L, Sun W, Xu C. . Two-fold improvement in chemical adsorption ability to achieve effective carbon dioxide electrolysis. Applied Catalysis B: Environmental, 2022, 317: 121754

[32] Liu Q, Song Y, Li R. . A vanadium-doped BSCF perovskite for CO₂ electrolysis in solid oxide electrolysis cells. International Journal of Hydrogen Energy, 2021, 46(38): 19814–19821

[33] Hu F, Ling Y, Fang S. . Engineering dual-exsolution on self-assembled cathode to achieve efficient electrocatalytic CO₂ reduction. Applied Catalysis B: Environmental, 2023, 337: 122968

[34] Wang Z, Tan T, Du K. . A high-entropy layered perovskite coated with in situ exsolved core-shell CuFe@FeO_x nanoparticles for efficient CO₂ electrolysis. Advanced Materials, 2024, 36(11): 2312119

[35] Akhmadjonov A, Bae K T, Lee K T. Novel perovskite oxide hybrid nanofibers embedded with nanocatalysts for highly efficient and durable electrodes in direct CO₂ electrolysis. Nano-Micro Letters, 2024, 16(1): 93

[36] Han F, Wang Z, Zhang S. . Highly efficient perovskite-based fuel electrodes for solid oxide electrochemical cells via iin-situ nanoparticle exsolution and electron conduction enhancement. Applied Catalysis B: Environment and Energy, 2025,

[37] Liu Q, Shen F, Song G. . Tailoring ion ordering in perovskite oxide for high-temperature oxygen evolution reaction. Angewandte Chemie International Edition, 2023, 62(32): e202307057

[38] Li J, Wu Z, Shen Y. . Suppressing surface segregation by introducing lanthanides to enhance high-temperature oxygen evolution reaction activity and durability. Journal of Physics: Energy, 2025, 7(2): 025002

[39] Yang C, Wang Z, Tan Y. . Interface engineering of La_0.6Sr_0.4Co_0.2Fe_0.8O_3−δ/Gd_0.1Ce_0.9O_1.95 heterostructure oxygen electrode for solid oxide electrolysis cells with enhanced CO₂ electrolysis performance. Chemical Engineering Journal, 2024, 498: 155461

[40] Yang K, Wang Y, Jiang L. . Cobalt-free perovskite Ba_0.95La_0.05FeO_3−δ as efficient and durable oxygen electrode for solid oxide electrolysis cells. International Journal of Hydrogen Energy, 2023, 48(71): 27464–27472

[41] Wu K T, Matsuda J, Staykov A. . Crucial role of self-exsolved heterostructured cermet nanoparticles in highly active spinel electrodes for CO₂/H₂O co-electrolysis. Advanced Energy Materials, 2023, 13(41): 2301042

[42] Wu K, Ishihara T. Superior syngas product control of La(Sr)Fe(Mn)O₃ perovskite in high-temperature CO₂/H₂O co-electrolysis. Applied Catalysis B. Environment and Energy, 2024, 357: 124335

[43] Zhang N, Naden A, Zhang L. . Enhanced CO₂ electrolysis through Mn substitution coupled with Ni exsolution in lanthanum calcium titanate electrodes. Advanced Materials, 2024, 36(19): 2308481

[44] Bausá N, Escolástico S, Serra J M. Direct CO₂ conversion to syngas in a BaCe_0.2Zr_0.7Y_0.1O_3−δ-based proton-conducting electrolysis cell. Journal of CO₂ Utilization, 2019, 34: 231–238

[45] Li W, Luo J. High-temperature electrochemical devices based on dense ceramic membranes for CO₂ conversion and utilization. Electrochemical Energy Reviews, 2021, 4(3): 518–544

[46] Liu F, Chen Z, Zhou H. . Highly efficient CH₄-assisted CO₂ electrolysis for syngas production in a quasi-symmetric Ni-ceramic electrolyzer. Journal of Power Sources, 2024, 609: 234703

[47] Dong C, Jiang F, Yang L. . Enhancing electrocatalytic reforming of CO₂/CH₄ with in situ exsolved metal-oxide interfaces in a solid oxide electrolysis cell. Separation and Purification Technology, 2022, 299: 121714

[48] Song Y, Liu T, Feng W. . Atomically dispersed Ru species induced by strong metal-support interaction for electrochemical methane reforming. Journal of the American Chemical Society, 2024, 146(46): 31825–31835

[49] Guo Y, Wang S, Li R. . In situ exsolved CoFe alloy nanoparticles for stable anodic methane reforming in solid oxide electrolysis cells. Joule, 2024, 8(7): 2016–2032

[50] Xie K, Zhang Y, Meng G. . Direct synthesis of methane from CO₂/H₂O in an oxygen-ion conducting solid oxide electrolyser. Energy & Environmental Science, 2011, 4(6): 2218–2222

[51] Chen L, Chen F, Xia C. Direct synthesis of methane from CO₂–H₂O co-electrolysis in tubular solid oxide electrolysis cells. Energy & Environmental Science, 2014, 7(12): 4018–4022

[52] Lei L, Liu T, Fang S. . The co-electrolysis of CO₂–H₂O to methane via a novel micro-tubular electrochemical reactor. Journal of Materials Chemistry. A, Materials for Energy and Sustainability, 2017, 5(6): 2904–2910

[53] Błaszczak P, Zając M, Ducka A. . High-temperature Co-electrolysis of CO₂/H₂O and direct methanation over Co-impregnated SOEC. Bimetallic synergy between Co and Ni. International Journal of Hydrogen Energy, 2022, 47(82): 35017–35037

[54] Duan C, Kee R, Zhu H. . Highly efficient reversible protonic ceramic electrochemical cells for power generation and fuel production. Nature Energy, 2019, 4(3): 230–240

[55] Li M, Hua B, Wang L. . Switching of metal–oxygen hybridization for selective CO₂ electrohydrogenation under mild temperature and pressure. Nature Catalysis, 2021, 4(4): 274–283

[56] Pan Z, Duan C, Pritchard T. . High-yield electrochemical upgrading of CO₂ into CH₄ using large-area protonic ceramic electrolysis cells. Applied Catalysis B: Environmental, 2022, 307: 121196

[57] Ye Y, Lee W, Pan J. . Tuning the product selectivity of CO₂/H₂O co-electrolysis using CeO₂-modified proton-conducting electrolysis cells. Energy & Environmental Science, 2023, 16(7): 3137–3145

[58] Zhu C, Hou S, Hu X. . Electrochemical conversion of methane to ethylene in a solid oxide electrolyzer. Nature Communications, 2019, 10(1): 1173

[59] Song Y, Lin L, Feng W. . Interfacial enhancement by γ-Al₂O₃ of electrochemical oxidative dehydrogenation of ethane to ethylene in solid oxide electrolysis cells. Angewandte Chemie International Edition, 2019, 58(45): 16043–16046

[60] Ye L, Duan X, Xie K. Electrochemical oxidative dehydrogenation of ethane to ethylene in a solid oxide electrolyzer. Angewandte Chemie International Edition, 2021, 60(40): 21746–21750

[61] Ye L, Shang Z, Xie K. Selective oxidative coupling of methane to ethylene in a solid oxide electrolyser based on porous single-crystalline CeO₂ monoliths. Angewandte Chemie International Edition, 2022, 61(32): e202207211

[62] Sun X, Yang H, Chen B. . Electrochemical activation of surface oxygen for efficient oxidative dehydrogenation reaction at elevated temperatures. ACS Catalysis, 2024, 14(8): 5827–5837

[63] He X, Huang X, Sun H. . Electrochemical oxidative dehydrogenation of ethane to ethylene in a solid oxide electrolysis cell with in situ grown metal-oxide interface active electrodes. International Journal of Hydrogen Energy, 2024, 79: 1030–1036

[64] Qin M, Zhang S, Sun W. . Novel Sr_1.95Fe_1.4Co_0.1Mo_0.5O_6‒δ anode heterostructure for efficient electrochemical oxidative dehydrogenation of ethane to ethylene by solid oxide electrolysis cells. Ceramics International, 2023, 49(18): 30178–30186

[65] Zhang S, Xu C, Ren R. . Self-assembly dual active site nanocomposite anode Ce_0.6Mn_0.3Fe_0.1O_2-δ/NiFe/MnO_x for electrooxidative dehydrogenation of ethane to ethylene. ACS Applied Materials & Interfaces, 2024, 16(3): 3451–3459

[66] Zhang X, Ye L, Li H. . Electrochemical dehydrogenation of ethane to ethylene in a solid oxide electrolyzer. ACS Catalysis, 2020, 10(5): 3505–3513

[67] Wang L, Pérez-Fortes M, Madi H. . Optimal design of solid-oxide electrolyzer based power-to-methane systems: A comprehensive comparison between steam electrolysis and co-electrolysis. Applied Energy, 2018, 211: 1060–1079

[68] Al-Kalbani H, Xuan J, García S. . Comparative energetic assessment of methanol production from CO₂: Chemical versus electrochemical process. Applied Energy, 2016, 165: 1–13

[69] Zong Z, Koers N, Cai G. . CO₂-to-methanol: Economic and environmental comparison of emerging and established technologies with dry reforming and methane pyrolysis. Chemical Engineering Journal, 2024, 487: 150274

[70] Ferguson K M, Saafan H, Wildeboer E K H. . Production of carbon neutral methanol using co-electrolysis of CO₂ and steam in solid oxide electrolysis cell in tandem with direct air capture. ECS Transactions, 2021, 103(1): 663–676

[71] Zhang H, Desideri U. Techno-economic optimization of power-to-methanol with co-electrolysis of CO₂ and H₂O in solid-oxide electrolyzers. Energy, 2020, 199: 117498

[72] Khan M S, Abid M, Chen C. . Sustainable hydrogen storage and methanol synthesis through solar-powered co-electrolysis using SOEC. Energy Storage, 2024, 6(8): e70095

[73] Zhang Y, Li A, Fei Y. . Techno-economic assessment of electro-synthetic fuel based on solid oxide electrolysis cell coupled with Fischer-Tropsch strategy. Journal of CO₂ Utilization, 2024, 86: 102905

[74] Pratschner S, Hammerschmid M, Müller S. . Off-grid vs. grid-based: Techno-economic assessment of a power-to-liquid plant combining solid-oxide electrolysis and Fischer-Tropsch synthesis. Chemical Engineering Journal, 2024, 481: 148413

[75] Chatenet M, Pollet B G, Dekel D R. . Water electrolysis: From textbook knowledge to the latest scientific strategies and industrial developments. Chemical Society Reviews, 2022, 51(11): 4583–4762

[76] Precedence Research. Electrolyzer market size, share, and trends 2024 to 2033. 2024, ,

[77] Can W, Cai W, Zhang S. . Global carbon neutrality annual progress report. 2024–10, available at website of Tsinghua University. , ,

[78] Zheng Y, Gao L, He S. . Reduction potential of the energy penalty for CO₂ capture in CCS. Frontiers in Energy, 2023, 17(3): 390–399

[79] Zhu F, Ge J, Gao Y. . Molten salt electro-preparation of graphitic carbons. Exploration, 2023, 3(1): 20210186

[80] Habibzadeh F, Mardle P, Zhao N. . Ion exchange membranes in electrochemical CO₂ reduction processes. Electrochemical Energy Reviews, 2023, 6(1): 26

[81] Tang T, Wang Z, Guan J. Achievements and challenges of copper-based single-atom catalysts for the reduction of carbon dioxide to C₂₊ products. Exploration, 2023, 3(5): 20230011

[82] Prakash J, Chen Z, Saini S. . Advancements on metal oxide semiconductor photocatalysts in photo-electrochemical conversion of carbon dioxide into fuels and other useful products. Frontiers in Energy, 2024, 18(2): 187–205

[83] Xue J, Chen Z, Zhang Y. . A review on plasmonic enhancement of activity and selectivity in electrocatalytic CO₂ reduction. Frontiers in Energy, 2024, 18(4): 399–417

[84] Hossain M N, Zhang L, Neagu R. . Free-standing single-atom catalyst-based electrodes for CO₂ reduction. Electrochemical Energy Reviews, 2024, 7(1): 5

[85] Li F, Li Y, Chen H. . Impact of strain-induced changes in defect chemistry on catalytic activity of Nd₂NiO_4+δ electrodes. ACS Applied Materials & Interfaces, 2018, 10(43): 36926–36932

[86] Song Y, Zhang X, Xiao Z. . Coupled amorphous NiFeP/crystalline Ni₃S₂ nanosheets enables accelerated reaction kinetics for high current density seawater electrolysis. Applied Catalysis B. Environment and Energy, 2024, 352: 124028

RIGHTS & PERMISSIONS

Higher Education Press 2025