Hydrogen storage is a critical component in transition to clean energy systems and the promotion of sustainable practices across various industries. The primary technical challenge lies in designing adsorbent materials that effectively balance both volumetric and gravimetric storage capabilities while ensuring operational reliability. Achieving this balance is essential for the efficient and practical application of hydrogen in fuel-based systems. Recently, in Nature Chemistry, Stoddart et al. introduced a straightforward and precise method: multivalent hydrogen bonding facilitates molecular linkage at defined nodal points in hydrogen-bonded organic frameworks (HOFs). This methodology demonstrates simultaneous optimization of hydrogen storage performance, achieving notable volumetric (53.7 g/L) and gravimetric (9.3 wt%) capacities under dynamic thermo-pressure cycling conditions.
The increasing accumulation of discarded plastics has already caused serious environmental pollution. Simple landfills and incineration will inevitably lead to the loss of the abundant carbon resources contained in plastic waste. In contrast, photoconversion technology provides a green and sustainable solution to the global plastic waste crisis by converting plastics into hydrogen fuel and valuable chemicals. This review briefly introduces the advantages of photoconversion technology and highlights recent research progress, with a focus on photocatalyst design as well as the thermodynamics and kinetics of the reaction process. It discusses in detail the degradation of typical common plastic types into hydrogen and fine chemicals via photoconversion. Additionally, it outlines future research directions, including the application of artificial intelligence in catalyst design. Although photocatalytic technology remains at the laboratory stage, with challenges in catalyst performance and industrial scalability, the potential for renewable energy generation and plastic valorization is promising.
Direct air capture (DAC) is an emerging technology aimed at mitigating global warming. However, conventional DAC technologies and the subsequent utilization processes are complex and energy-intensive. An integrated system of direct air capture and utilization (IDACU) via in-situ catalytic conversion to fuels and chemicals is a promising approach, although it remains in the early stages of development. This review examines the current technical routes of IDACU, including solid-based dual-functional materials (DFMs) through thermo-catalysis, IDACU using liquid sorbents with thermo-catalysis, and non-thermal conversion methods. It covers the basic principles, reaction conditions, main products, material types, and the existing problems and challenges associated with these technical routes. Additionally, it discusses the recent advancements in solid-based DFMs for IDACU, with particular attention to the differences in material characteristics between carbon capture from flue gases (ICCU) and DAC. While IDACU technology holds significant promise, it still faces numerous challenges, especially in the design of advanced materials.
Proton exchange membrane fuel cells (PEMFCs) have attracted significant attention as sustainable energy technologies due to their efficient energy conversion and fuel flexibility. However, several challenges remain, such as low catalytic activity of fuel cell membrane electrode assembly (MEA), insufficient mass transfer performance, and performance degradation caused by catalyst deactivation over long period of operation. These issues are especially significant at high current densities, limiting both efficiency and operational lifespan. Mesoporous carbon materials, characterized by a high specific surface area, tunable pore structure, and excellent electrical conductivity, are emerging as crucial components for enhancing power density, mass transfer efficiency, and durability of PEMFCs. This review first discusses the properties and advantages of mesoporous carbon and outlines various synthetic strategies, including hard template, soft template, and template-free approaches. It then comprehensively examines the applications of mesoporous carbon in PEMFCs, focusing on their effects on the catalyst and gas diffusion layer. Finally, it concludes with future perspectives, emphasizing the need for further research to fully exploit the potential of mesoporous carbon in PEMFCs.
Diethyl ether (DEE, C4H10O) has emerged as a promising renewable alternative to conventional diesel fuels, offering potential solutions for sustainable energy development. This review systematically examines the fundamental combustion characteristics of DEE, including pyrolysis and oxidation behaviors, kinetic modeling, and actual combustion characteristics. It comprehensively summarized the key research progress and main findings in this field. Research has indicated that DEE demonstrates excellent ignition performance, whether used alone or as an additive, and significantly reduces soot formation during combustion by limiting the discharge of C3–C4 hydrocarbon species. However, a complete mechanistic understanding of DEE combustion still remains limited by the lack of key coupling reaction pathways, which directly restricted the accuracy of the reaction kinetic model. At the actual combustion level in devices, the effects of DEE on engine performance, combustion behavior, and emissions has been investigated. Although a large number of experiments have confirmed that DEE has a significant improvement effect in the above aspects, certain performance degradation phenomena and their internal mechanism still require further elucidation. Based on these insights, this review also analyzes the key challenges facing DEE in practical applications and discusses possible solutions, aiming to build a complete research framework spanning from fundamental studies to engineering application future development.
Single-atom transition metal-nitrogen-doped carbons (SA M-N-Cs) catalysts are promising alternatives to platinum-based catalysts for the oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs). However, enhancing their performance for practical applications remains a significant challenge. This review summarizes recent advances in enhancing the intrinsic activity of SA M-N-C catalysts through various strategies, such as tuning the coordination environment and local structure of central metal atoms, heteroatom doping, and the creation of dual-/multi metal sites. Additionally, it discusses methods to increase the density of M-Nx active sites, including chelation, defect capture, cascade anchoring, spatial confinement, porous structure design, and secondary doping. Finally, it outlines future directions for developing highly active and stable SA M-N-C catalysts, providing a comprehensive framework for the design of advanced catalysts.
Sodium-ion batteries (SIBs) exhibit significant potential for large-scale energy storage systems due to the abundance and low cost of sodium resources. Triggering lattice oxygen redox (LOR) in P2-type transition metal oxides is considered a promising approach to enhance energy density in SIB cathodes, providing high operating potential and substantial capacity. However, irreversible phase transitions associated with LOR, particularly from prisms (P-type stacking) to octahedrons (O-type stacking), lead to severe structural distortions and sluggish Na+ diffusion kinetics. In this work, an Al-substitution strategy is proposed to suppress the formation of O-type stacking and instead promote the formation of a beneficial Z phase. The flexible Al–O bonds accommodate asymmetric variations in their occupied states during the sodiation process, mitigating local structural distortions through Al–O bond contraction. Stabilization of the local structure ensures the maintenance of a robust Na+ diffusion pathway. As a result, the Al-substituted cathode achieves a low Na+ diffusion barrier of 0.47 eV and delivers a capacity of 86 mAh/g even at a high current density of 1 A/g within 1.5–4.5 V, maintaining 62.5% capacity retention over 100 cycles.
Electrochemical CO2 reduction (CO2RR) is a promising technology for mitigating global climate change. The catalyst layer (CL), where the reduction reaction occurs, plays a pivotal role in determining mass transport and electrochemical performance. However, accurately characterizing local structures and quantifying mass transport remains a significant challenge. To address these limitations, a systematic characterization framework based on deep learning (DL) is proposed. Five semantic segmentation models, including Segformer and DeepLabV3plus, were compared with conventional image processing techniques, among which DeepLabV3plus achieved the highest segmentation accuracy (> 91.29%), significantly outperforming traditional thresholding methods (72.35%–77.42%). Experimental validation via mercury intrusion porosimetry (MIP) confirmed its capability to precisely extract key structural parameters, such as porosity and pore size distribution. Furthermore, a series of ionomer content gradient experiments revealed that a CL with an ionomer/catalyst (I/C) ratio of 0.2 had the optimal pore network structure. Numerical simulations and electrochemical tests demonstrated that this CL enabled a twofold increase in gas diffusion distance, thereby promoting long-range mass transport and significantly enhancing CO production rates. This work establishes a multi-scale analysis framework integrating “structural characterization, mass transport simulation, and performance validation,” offering both theoretical insights and practical guidance for the rational design of CO2RR CLs.
Developing low-cost and high-performance acid-resistant electrocatalysts is essential for the industrialization of hydrogen production via proton exchange membrane water electrolysis. Herein, an acid-stable bimetal phosphide (NiCoP) catalyst wrapped around silver nanowires (Ag NWs), forming a seamless conductive core-shell structure (NiCoP@Ag NWs), is reported to enhance the hydrogen evolution reaction (HER). The incorporation of Ag NWs creates an uninterrupted conductive network that facilitates efficient electron transfer and provides a large electrolyte-accessible surface area for mass transport. The synergistic interaction among Ni, Co, and P further optimizes electronic structure and decreases the energy barrier of NiCoP@Ag NWs for H* adsorption and desorption. More importantly, the distinctive core-shell structure imparts outstanding acid resistance to the catalyst. Notably, NiCoP@Ag NWs displays remarkable HER performance, with a low overpotential of 109 mV (significantly lower than Ni2P@Ag NWs at 144 mV and Co2P@Ag NWs at 174 mV) at a current density of 10 mA/cm2, along with excellent durability exceeding 100 h in acidic media. These features surpass most reported non-noble metal catalysts, demonstrating extraordinary potential for practical hydrogen production via acidic water electrolysis.
NH3 has emerged as a promising candidate for low-carbon gas turbines, with NOx emission issues being mitigated by air-staged combustion. However, the role of fuel/air mixing quality (represented by unmixedness) in NOx formation in NH3 systems remains poorly explored. In this study, the characteristics of NOx formation under the effects of unmixedness have been numerically investigated using an NH3/CH4 fired air-staged model combustor consisting of perfectly stirred reactors (PSRs) and plug flow reactors (PFRs), employing the 84-species, 703-reaction Tian mechanism under H/J heavy duty gas turbine conditions. It was found that a primary-stage equivalence ratio of 1.2–1.5 corresponds to a low NOx formation region under perfectly mixed fuel and air conditions. In this region, a relatively low NOx formation is achieved when the unmixedness is less than 0.12 and NOx formation exhibits low sensitivity to fuel/air unmixedness. Based on these findings and the fact that the air-staged combustion loses its advantage in reducing NOx emissions when the unmixedness exceeds 0.12 across all equivalence ratios, recommended mixing quality thresholds for different equivalence ratios are proposed to guide combustor design and operation optimization. A parametric study of chemical reaction pathways at different unmixedness levels in the two stages demonstrates that NOx is mainly formed in the main combustion zone of the secondary stage via the HNO pathway, which results in NOx formation rising to thousand ppm when unmixedness exceeds 0.3, although NOx reduction through NHi and N2O pathways partially offsets contributions from the HNO and thermal NOx pathways. To leverage the NOx reduction potential of the NHi and N2O pathways, the residence time in both stages should be carefully adjusted to help suppress NOx to as low as 48 ppm. The results of this study are important for engineering applications, providing guidance for the design of NH3 fired combustors aimed at significantly reducing NOx formation.
This study employs the method of embedding voltage leads within three cells of an electrolysis stack to investigate the quantitative impact of the electrolysis cells and their interfaces on overall stack performance. A 900-h stability test was conducted at a constant temperature of 750 °C with a current density of 500 mA/cm2 and 60 vol.% (volume fraction) water steam content. The results indicate the electrolysis voltage of the stack increased by 0.213 V, while the voltage across the three cells increased by 0.268 V. Post-mortem analysis reveals changes in the three-phase boundary (TPB) and porosity of the Ni-YSZ electrodes across different cells. These structural changes explain the variations in both ohmic resistance and polarization resistance. In contrast, the voltage drop across the current-collecting interface between the interconnect and the cell decreases by 0.055 V, accounting for 25.82% of the total stack degradation. Improved interface contact helps inhibit stack degradation. Future work will further investigate the stability of stack components and their interfaces, aiming to optimize stack design.
The oxygen reduction reaction (ORR) plays a crucial role in key processes of fuel cells and zinc-air batteries. To enable commercialization, reducing the platinum (Pt) content and increasing the specific activity per unit mass is essential. A promising approach involves synthesizing of Fe-N-C precursors via the polyaniline (PANI) pathway, which ensures a uniform distribution of Fe-N-C species and facilitates the subsequent adsorption of platinum ions. This leads to the formation of Pt-Fe bimetallic alloys. The synergistic interaction between Pt and Fe-N-C sites promotes the homogeneous dispersion of Pt and the formation of smaller particle sizes, which in turn enhances intrinsic activity and stability of the catalyst. Notably, the Pt/Fe-N-C catalyst, featuring an ultra-low Pt loading of just 1.79 wt%, exhibits a remarkable doubling of mass activity compared to conventional catalysts. Moreover, zinc-air batteries using this catalyst achieve an impressive peak power density of 200 mW/cm2.
Existing swirling combustion technology, which relies on faulty coal, is unable to meet deep peak shaving demands without auxiliary methods. This paper developed a deep peak regulation burner (DPRB) to achieve stable combustion at 15%–30% of the boiler’s rated load without auxiliary support. Gas-particle tests, industrial trials, and transient numerical simulations were conducted to evaluate the burner’s performance. At full rated load, the DPRB formed a central recirculation zone (RZ) with a length of 1.5d and a diameter of 0.58d (where d represents the outlet diameter). At 40%, 20%, and 15% rated loads, the RZ became annular, with diameters of 0.30d, 0.40d, and 0.39d, respectively, with a length of 1.0d. At 20% and 15% rated loads, the recirculation peak and the range of particle volume flux were comparable to those at 40% rated load. The prototype burner demonstrated that, without oil support, the gas temperature within 0 to 1.8 m from the primary air outlet remained below 609 °C, insufficient to ignite faulty coal. As the load rate increased from 20% to 30%, the prototype’s central region temperature remained low, with a maximum of 750 °C between 0 and 2.0 m. In contrast, the DPRB’s central region temperature reached 750 °C at around 0.65–0.70 m. At a 3%·min‒1 load-up rate, when the load increased from 20% to 30%, the prototype burner extinguished after 30 s. However, the DPRB maintained stable combustion throughout the process.
To mitigate the adverse effects of high concentrations of Cl− ions in seawater on electrolysis efficiency, it is essential to develop efficient and stable electrocatalysts. Based on this need, CuCo-ZIF NCs were used as a precursor to synthesize a CuCo-TA@FeOOH heterojunction composites, specifically designed for the oxygen evolution reaction (OER) in alkaline seawater, through a combination of acid etching and a self-growth method. The resulting material exhibits an OER overpotential of 234 mV at 10 mA/cm2 in alkaline freshwater and 256 mV at 10 mA/cm2 in seawater electrolyte. This performance is attributed to synergistic interactions at the heterojunction interfaces, which enhances the specific surface area, offers abundant active sites, and improves mass transfer efficiency, thereby increasing catalytic activity. Moreover, at a current density of 100 mA/cm², it maintains stable performance for up to 300 h without deactivation. This remarkable stability and corrosion resistance stems from the synergistic effect at the CoOOH and FeOOH interface formed during reconstruction, which facilitates electron transfer, optimizes the electronic structure during the reaction process, and effectively suppresses the chlorine evolution reaction (CER). This study offers a valuable reference for the rational design of high-performance electrocatalysts for alkaline seawater oxidation.
Gallium nitride (GaN) nanostructures are highly promising for photoelectrochemical (PEC) water splitting due to their excellent electron mobility, chemical stability, and large surface area. However, the wide bandgap (~3.4 eV) of GaN limits its ability to absorb a broad spectrum of solar radiation, restricting its PEC performance. To address this limitation, MoS2/GaN nanorods (NRs) heterostructures for enhanced PEC applications were fabricated on thin tungsten foil using a combination of atmospheric pressure chemical vapor deposition (CVD) and laser molecular beam epitaxy (LMBE). The Raman spectroscopy and X-ray diffraction revealed the hexagonal phase of GaN and MoS2. X-ray photoelectron spectroscopy examined the electronic states of the GaN and MoS2. PEC measurements revealed that the MoS2-decorated GaN NRs exhibited a photocurrent density of approximately172 µA/cm2, nearly 2.5-fold compared to bare GaN NRs (~70 µA/cm2). The increased photocurrent density is ascribed to the Type II band alignment between MoS2 and GaN, which promotes effective charge separation, the decrease in charge transfer resistance, and the increase in active sites. The findings of this work underscore that the CVD and LMBE technique fabricated MoS2/GaN heterostructures on W metal foil substrate can provide the vital strategy to raise the PEC efficiency toward solar water splitting.
Proton exchange membrane (PEM) electrolyzer (EL) is regarded as a promising technology for hydrogen generation, offering load flexibility for electric grids (EGs), especially those with a high penetration of renewable energy (RE) sources. This paper proposes a PEM-focused economic dispatch strategy for EG integrated with wind-electrolysis systems. Existing strategies commonly assume a constant efficiency coefficient to model the EL, while the proposed strategy incorporates a bottom-up PEM EL model characterized by a part-load efficiency curve, which accurately represents the nonlinear hydrogen production performance, capturing efficiency variations at different loads. To model this, it first establishes a 0D electrochemical model to derive the polarization curve. Next, it accounts for the hydrogen and oxygen crossover phenomena, represented by the Faraday efficiency, to correct the stack efficiency curve. Finally, it includes the power consumption of ancillary equipment to obtain the nonlinear part-load system efficiency. This strategy is validated using the PJM-5 bus test system with coal-fired generators (CFGs) and is compared with a simple EL model using constant efficiency under three scenarios. The results show that the EL modeling method significantly influences both the dispatch outcome and the economic performance. Sensitivity analyses on coal and hydrogen prices indicate that, for this case study, the proposed strategy is economically advantageous when the coal price is below 121.6 $/tonne. Additionally, the difference in total annual operating cost between using the efficiency curve anda constant efficiency to model becomes apparent when the hydrogen price ranges from 2.9 to 5.4 $/kg.
The development of anti-corrosion and anti-poison electrocatalysts for both the hydrogen oxidation reaction (HOR) and oxygen reduction reaction (ORR) is of great importance for effective applications of proton exchange membrane fuel cells (PEMFCs). In this study, a non-carbon supported catalyst, Pt/TiO2-Ov, enriched with oxygen vacancies (Ov), is successfully synthesized using a microwave-assisted method. This catalyst is developed as a bifunctional electrocatalyst with superior contamination tolerance, enabling efficient HOR and ORR performance. The electronic metal-support interaction (EMSI) is leveraged to facilitate electron transfer between Pt and Ti atoms, induced by the formation of oxygen vacancy channels in the small-sized, high surface area TiO2-Ov support. Notably, TiO2-Ov has a lower bandgap than commercial TiO2, enhancing its catalytic properties. In a 0.1 mol/L HClO4 electrolyte, the normalized Pt mass activity (jk,m) and specific activity (j0,s) of Pt/TiO2-Ov are 1.24 times higher than those of commercial Pt/C. Furthermore, Pt/TiO2-Ov catalyst exhibits minimal current density decay after a prolonged durability testing under hydrogen and oxygen atmospheres. Remarkably, under a H2/(1000×10–6) CO atmosphere, the relative retention rate of Pt/TiO2-Ov significantly exceeds that of Pt/C catalyst, demonstrating its superior CO tolerance and promising potential for practical applications in PEMFCs. This study highlights the critical role of the strong metal-support interaction between the reducible oxide support and the noble metal Pt in improving long-term performance and CO poisoning resistance.