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  • HIGHLIGHTS
    Wenzhong SHEN, Yixin ZHAO, Feng LIU
    Frontiers in Energy, 2024, 18(1): 8-15. https://doi.org/10.1007/s11708-024-0937-5
  • REVIEW ARTICLE
    Simiao SHA, Riyue GE, Ying LI, Julie M. CAIRNEY, Rongkun ZHENG, Sean LI, Bin LIU, Jiujun ZHANG, Wenxian LI
    Frontiers in Energy, 2024, 18(3): 265-290. https://doi.org/10.1007/s11708-023-0892-6

    High entropy materials (HEMs) have developed rapidly in the field of electrocatalytic water-electrolysis for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) due to their unique properties. In particular, HEM catalysts are composed of many elements. Therefore, they have rich active sites and enhanced entropy stability relative to single atoms. In this paper, the preparation strategies and applications of HEM catalysts in electrochemical water-electrolysis are reviewed to explore the stabilization of HEMs and their catalytic mechanisms as well as their application in support green hydrogen production. First, the concept and four characteristics of HEMs are introduced based on entropy and composition. Then, synthetic strategies of HEM catalysts are systematically reviewed in terms of the categories of bottom-up and top-down. The application of HEMs as catalysts for electrochemical water-electrolysis in recent years is emphatically discussed, and the mechanisms of improving the performance of electrocatalysis is expounded by combining theoretical calculation technology and ex-situ/in situ characterization experiments. Finally, the application prospect of HEMs is proposed to conquer the challenges in HEM catalyst fabrications and applications.

  • COMMENTS
    Baowen ZHOU, Shuhui SUN
    Frontiers in Energy, 2024, 18(1): 122-124. https://doi.org/10.1007/s11708-023-0870-z
  • MINI REVIEW
    Yixin LI, Sharif Md. SADAF, Baowen ZHOU
    Frontiers in Energy, 2024, 18(1): 56-79. https://doi.org/10.1007/s11708-023-0881-9

    Sunlight-powered water splitting presents a promising strategy for converting intermittent and virtually unlimited solar energy into energy-dense and storable green hydrogen. Since the pioneering discovery by Honda and Fujishima, considerable efforts have been made in this research area. Among various materials developed, Ga(X)N/Si (X = In, Ge, Mg, etc.) nanoarchitecture has emerged as a disruptive semiconductor platform to split water toward hydrogen by sunlight. This paper introduces the characteristics, properties, and growth/synthesis/fabrication methods of Ga(X)N/Si nanoarchitecture, primarily focusing on explaining the suitability as an ideal platform for sunlight-powered water splitting toward green hydrogen fuel. In addition, it exclusively summarizes the recent progress and development of Ga(X)N/Si nanoarchitecture for photocatalytic and photoelectrochemical water splitting. Moreover, it describes the challenges and prospects of artificial photosynthesis integrated device and system using Ga(X)N/Si nanoarchitectures for solar water splitting toward hydrogen.

  • REVIEW ARTICLE
    Nan QI, Kang YAN, Yajuan YU, Rui LI, Rong HUANG, Lai CHEN, Yuefeng SU
    Frontiers in Energy, 2024, 18(2): 223-240. https://doi.org/10.1007/s11708-023-0891-7

    As the intersection of disciplines deepens, the field of battery modeling is increasingly employing various artificial intelligence (AI) approaches to improve the efficiency of battery management and enhance the stability and reliability of battery operation. This paper reviews the value of AI methods in lithium-ion battery health management and in particular analyses the application of machine learning (ML), one of the many branches of AI, to lithium-ion battery state of health (SOH), focusing on the advantages and strengths of neural network (NN) methods in ML for lithium-ion battery SOH simulation and prediction. NN is one of the important branches of ML, in which the application of NNs such as backpropagation NN, convolutional NN, and long short-term memory NN in SOH estimation of lithium-ion batteries has received wide attention. Reports so far have shown that the utilization of NN to model the SOH of lithium-ion batteries has the advantages of high efficiency, low energy consumption, high robustness, and scalable models. In the future, NN can make a greater contribution to lithium-ion battery management by, first, utilizing more field data to play a more practical role in health feature screening and model building, and second, by enhancing the intelligent screening and combination of battery parameters to characterize the actual lithium-ion battery SOH to a greater extent. The in-depth application of NN in lithium-ion battery SOH will certainly further enhance the science, reliability, stability, and robustness of lithium-ion battery management.

  • RESEARCH ARTICLE
    Mingkuan ZHANG, Xudong ZHANG, Luna GUO, Xuan LI, Wei RAO
    Frontiers in Energy, 2023, 17(6): 796-810. https://doi.org/10.1007/s11708-023-0877-5

    Liquid metal-based microchannel heat sinks (MCHSs) suffer from the low heat capacity of coolant, resulting in an excessive temperature rise of coolant and heat sink when dealing with high-power heat dissipation. In this paper, it was found that expanded space at the top of fins could distribute the heat inside microchannels, reducing the temperature rise of coolant and heat sink. The orthogonal experiments revealed that expanding the top space of channels yielded similar temperature reductions to changing the channel width. The flow and thermal modeling of expanded microchannel heat sink (E-MCHS) were analyzed by both using the 3-dimensional (3D) numerical simulation and the 1-dimensional (1D) thermal resistance model. The fin efficiency of E-MCHS was derived to improve the accuracy of the 1D thermal resistance model. The heat conduction of liquid metal in Z direction and the heat convection between the top surface of fins and the liquid metal could reduce the total thermal resistance (Rt). The above process was effective for microchannels with low channel aspect ratio, low mean velocity (Um) or long heat sink length. The maximum thermal resistance reduction in the example of this paper reached 36.0%. The expanded space endowed the heat sink with lower pressure, which might further reduce the pumping power (P). This rule was feasible both when fins were truncated (h2 < 0, h2 is the height of expanded channel for E-MCHS) and when over plate was raised (h2 > 0).

  • RESEARCH ARTICLE
    Ting DENG, Shuaiqiang JIA, Shitao HAN, Jianxin ZHAI, Jiapeng JIAO, Xiao CHEN, Cheng XUE, Xueqing XING, Wei XIA, Haihong WU, Mingyuan HE, Buxing HAN
    Frontiers in Energy, 2024, 18(1): 80-88. https://doi.org/10.1007/s11708-023-0898-0

    Electrocatalytic CO2 reduction (ECR) offers an attractive approach to realizing carbon neutrality and producing valuable chemicals and fuels using CO2 as the feedstock. However, the lack of cost-effective electrocatalysts with better performances has seriously hindered its application. Herein, a one-step co-electrodeposition method was used to introduce Zn, a metal with weak *CO binding energy, into Cu to form Cu/Zn intermetallic catalysts (Cu/Zn IMCs). It was shown that, using an H-cell, the high Faradaic efficiency of C2+ hydrocarbons/alcohols (FEC 2+) could be achieved in ECR by adjusting the surface metal components and the applied potential. In suitable conditions, FEC2+ and current density could be as high as 75% and 40 mA/cm2, respectively. Compared with the Cu catalyst, the Cu/Zn IMCs have a lower interfacial charge transfer resistance and a larger electrochemically active surface area (ECSA), which accelerate the reaction. Moreover, the *CO formed on Zn sites can move to Cu sites due to its weak binding with *CO, and thus enhance the C–C coupling on the Cu surface to form C2+ products.

  • REVIEW ARTICLE
    Hongxia LI, Khaja WAHAB AHMED, Mohamed A. ABDELSALAM, Michael FOWLER, Xiao-Yu WU
    Frontiers in Energy, 2024, 18(3): 291-307. https://doi.org/10.1007/s11708-024-0917-9

    Solar-driven hydrogen production from seawater attracts great interest for its emerging role in decarbonizing global energy consumption. Given the complexity of natural seawater content, photocatalytic vapor splitting offers a low-cost and safe solution, but with a very low solar-to-hydrogen conversion efficiency. With a focus on cutting-edge photothermal–photocatalytic device design and system integration, the recent research advances on vapor splitting from seawater, as well as industrial implementations in the past decades were reviewed. In addition, the design strategies of the key processes were reviewed, including vapor temperature and pressure control during solar thermal vapor generation from seawater, capillary-fed vaporization with salt repellent, and direct photocatalytic vapor splitting for hydrogen production. Moreover, the existing laboratory-scale and industrial-scale systems, and the integration principles and remaining challenges in the future seawater-to-hydrogen technology were discussed.

  • RESEARCH ARTICLE
    Jinlong WANG, Jin XIAO, Yingdong CHENG, Zhen HUANG
    Frontiers in Energy, 2023, 17(6): 811-821. https://doi.org/10.1007/s11708-022-0848-2

    Free-piston engine generators (FPEGs) can be applied as decarbonized range extenders for electric vehicles because of their high thermal efficiency, low friction loss, and ultimate fuel flexibility. In this paper, a parameter-decoupling approach is proposed to model the design of an FPEG. The parameter-decoupling approach first divides the FPEG into three parts: a two-stroke engine, an integrated scavenging pump, and a linear permanent magnet synchronous machine (LPMSM). Then, each of these is designed according to predefined specifications and performance targets. Using this decoupling approach, a numerical model of the FPEG, including the three aforementioned parts, was developed. Empirical equations were adopted to design the engine and scavenging pump, while special considerations were applied for the LPMSM. A finite element model with a multi-objective genetic algorithm was adopted for its design. The finite element model results were fed back to the numerical model to update the LPMSM with increased fidelity. The designed FPEG produced 10.2 kW of electric power with an overall system efficiency of 38.5% in a stable manner. The model provides a solid foundation for the manufacturing of related FPEG prototypes.

  • REVIEW ARTICLE
    Zhijing ZHANG, Haoze ZHANG, Yaopeng WU, Wei YAN, Jiujun ZHANG, Yun ZHENG, Lanting QIAN
    Frontiers in Energy, 2024, 18(2): 141-159. https://doi.org/10.1007/s11708-024-0918-8

    The electrochemistry of cathode materials for sodium-ion batteries differs significantly from lithium-ion batteries and offers distinct advantages. Overall, the progress of commercializing sodium-ion batteries is currently impeded by the inherent inefficiencies exhibited by these cathode materials, which include insufficient conductivity, slow kinetics, and substantial volume changes throughout the process of intercalation and deintercalation cycles. Consequently, numerous methodologies have been utilized to tackle these challenges, encompassing structural modulation, surface modification, and elemental doping. This paper aims to highlight fundamental principles and strategies for the development of sodium transition metal oxide cathodes. Specifically, it emphasizes the role of various elemental doping techniques in initiating anionic redox reactions, improving cathode stability, and enhancing the operational voltage of these cathodes, aiming to provide readers with novel perspectives on the design of sodium metal oxide cathodes through the doping approach, as well as address the current obstacles that can be overcome/alleviated through these dopant strategies.

  • MINI REVIEW
    Junwen CAO, Yikun HU, Yun ZHENG, Wenqiang ZHANG, Bo YU
    Frontiers in Energy, 2024, 18(2): 128-140. https://doi.org/10.1007/s11708-023-0908-2

    The Haber-Bosch process is the most widely used synthetic ammonia technology at present. Since its invention, it has provided an important guarantee for global food security. However, the traditional Haber-Bosch ammonia synthesis process consumes a lot of energy and causes serious environmental pollution. Under the serious pressure of energy and environment, a green, clean, and sustainable ammonia synthesis route is urgently needed. Electrochemical synthesis of ammonia is a green and mild new method for preparing ammonia, which can directly convert nitrogen or nitrate into ammonia using electricity driven by solar, wind, or water energy, without greenhouse gas and toxic gas emissions. Herein, the basic mechanism of the nitrogen reduction reaction (NRR) to ammonia and nitrate reduction reaction (NO3 RR) to ammonia were discussed. The representative approaches and major technologies, such as lithium mediated electrolysis and solid oxide electrolysis cell (SOEC) electrolysis for NRR, high activity catalyst and advanced electrochemical device fabrication for NO3 RR and electrochemical ammonia synthesis were summarized. Based on the above discussion and analysis, the main challenges and development directions for electrochemical ammonia synthesis were further proposed.

  • RESEARCH ARTICLE
    Bin WANG, Bei AN, Xiaoqian LI, Shaohua SHEN
    Frontiers in Energy, 2024, 18(1): 101-109. https://doi.org/10.1007/s11708-023-0894-4

    It has been widely reported that, for faceted nanocrystals, the two adjacent facets with different band levels contribute to promoted charge separation, and provide active sites for photocatalytic reduction and oxidation reaction, respectively. In such cases, only one family of facets can be used for photocatalytic hydrogen evolution. Herein, by using SrTiO3 nanocrystals enclosed by {023} and {001} facets as a model photocatalyst, this paper proposed a strategy to achieve the full-facets-utilization of the nanocrystals for photocatalytic hydrogen via chemically depositing Pt nanoparticles on all facets. The photo-deposition experiment of CdS provided direct evidence to demonstrate that the {023} facets which were responsible for photooxidation reaction can be function-reversed for photocatalytic hydrogen evolution after depositing Pt nanoparticles, together with the {001} facets. Thus, the full-facets-utilization led to a much-improved activity for photocatalytic hydrogen, in contrast to those SrTiO3 nanocrystals with only {001} facets deposited by Pt nanoparticles via a photo-deposition method.

  • PERSPECTIVES
    C. C. CHAN, Wei HAN, Hanlei TIAN, Yanbing LIU, Tianlu MA, C. Q. JIANG
    Frontiers in Energy, 2023, 17(6): 693-703. https://doi.org/10.1007/s11708-023-0890-8

    The automotive industry is in the midst of a groundbreaking revolution, driven by the imperative to achieve intelligent driving and carbon neutrality. A crucial aspect of this transformation is the transition to electric vehicles (EVs), which necessitates widespread changes throughout the entire automotive ecosystem. This paper examines the challenges and opportunities of this transition, including automotive electrification, intelligence-connected transportation system, and the potential for new technologies such as hydrogen fuel cells. Meanwhile, it discusses the key technologies and progress of the hydrogen energy industry chain in the upstream hydrogen production, midstream hydrogen storage and transportation, downstream hydrogen station construction and hydrogen fuel cells in turn. Finally, it proposes the directions for future layout, providing guidance for future development.

  • REVIEW ARTICLE
    Cheng YUAN, Shiming ZHANG, Jiujun ZHANG
    Frontiers in Energy, 2024, 18(2): 206-222. https://doi.org/10.1007/s11708-023-0907-3

    Platinum (Pt)-based materials are still the most efficient and practical catalysts to drive the sluggish kinetics of cathodic oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs). However, their catalysis and stability performance still need to be further improved in terms of corrosion of both carbon support and Pt catalyst particles as well as Pt loading reduction. Based on the developed synthetic strategies of alloying/nanostructuring Pt particles and modifying/innovating supports in developing conventional Pt-based catalysts, Pt single-atom catalysts (Pt SACs) as the recently burgeoning hot materials with a potential to achieve the maximum utilization of Pt are comprehensively reviewed in this paper. The design thoughts and synthesis of various isolated, alloyed, and nanoparticle-contained Pt SACs are summarized. The single-atomic Pt coordinating with non-metals and alloying with metals as well as the metal-support interactions of Pt single-atoms with carbon/non-carbon supports are emphasized in terms of the ORR activity and stability of the catalysts. To advance further research and development of Pt SACs for viable implementation in PEMFCs, various technical challenges and several potential research directions are outlined.

  • RESEARCH ARTICLE
    Yibo GAO, Erjiang HU, Bo HUANG, Zuohua HUANG
    Frontiers in Energy, 2023, 17(6): 751-762. https://doi.org/10.1007/s11708-023-0895-3

    Dehydrogenation of formic acid (FA) is considered to be an effective solution for efficient storage and transport of hydrogen. For decades, highly effective catalysts for this purpose have been widely investigated, but numerous challenges remain. Herein, the PdxAu1−x (x = 0, 0.2, 0.4, 0.5, 0.6, 0.8, 1) alloys over the whole composition range were successfully prepared and used to catalyze FA hydrogen production efficiently near room temperature. Small PdAu nanoparticles (5–10 nm) were well-dispersed and supported on the activated carbon to form PdAu solid solution alloys via the eco-friendly slow synthesis methodology. The physicochemical properties of the PdAu alloys were comprehensively studied by utilizing various measurement methods, such as X-ray diffraction (XRD), N2 adsorption–desorption, high angle annular dark field-scanning transmission electron microscope (HAADF-STEM), X-ray photoelectrons spectroscopy (XPS). Notably, owing to the strong metal-support interaction (SMSI) and electron transfer between active metal Au and Pd, the Pd0.5Au0.5 obtained exhibits a turnover frequency (TOF) value of up to 1648 h−1 (313 K, nPd+Au/nFA = 0.01, nHCOOH/nHCOONa = 1:3) with a high activity, selectivity, and reusability in the FA dehydrogenation.

  • RESEARCH ARTICLE
    Zhao-ting SHANG, Tang-ming LI, Bing-qian HU, Min LIU, Wang-ting LU, Fan YU, Yun ZHENG
    Frontiers in Energy, 2024, 18(3): 378-389. https://doi.org/10.1007/s11708-024-0924-x

    The use of two-dimensional (2D) layered metal-organic frameworks (MOFs) as self-sacrificial templates has been proven to be a successful method to create high-efficiency Selenium (Se)-containing electrocatalysts for overall water splitting. Herein, two strategies are then utilized to introduce Se element into the Co–Fe MOF, one being the etching of as-prepared MOF by SeO2 solution, and the other, the replacing of SCN with SeCN as the construction unit. The electrochemical activity of the pristine 2D MOF and their calcinated derivatives for catalyzing the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is evaluated and further discussed. It is found that the effect of introducing Se on improving electrochemical catalytic activity is significant for the HER process. Specifically, the calcinated derivative in the replacing method exhibits an overpotential of 235 mV for HER and 270 mV for OER at a current density of 10 mA/cm2. For comparing the two methods of introducing Se element into MOF, similar electrocatalytic activity can be achieved on the their calcinated derivatives. The high electrochemical performance of 2D CoFe-MOF derivatives may be resulted from the unique 2D hierarchical porous structure and strong synergistic effect between different components in the material.

  • RESEARCH ARTICLE
    Yang GE, Quanhao SHEN, Qi ZHANG, Naixu LI, Danchen LU, Zhaoming ZHANG, Zhiwei FU, Jiancheng ZHOU
    Frontiers in Energy, 2024, 18(1): 110-121. https://doi.org/10.1007/s11708-023-0899-z

    Metal-free graphitic carbon nitride (g-C3N4) has captured significant attention as a low-cost and efficient hydrogen production photocatalyst through. Effectively regulating the microstructure and accelerating the separation of photogenerated carriers remain crucial strategies for promoting the photocatalytic performance of this material. Herein, a novel sulfur–carbon co-doped g-C3N4 (SCCN) hierarchical microtubules filled with abundant nanosheets inside by thermal polymerization is reported. Numerous nanosheets create abundant pores and cavities inside the SCCN microtubes, thereby increasing the specific surface area of g-C3N4 and providing sufficient reactant attachment sites. Besides, the hierarchical structure of SCCN microtubules strengthens the reflection and scattering of light, and the utilization of visible light is favorably affected. More importantly, co-doping S and C has greatly improved the photocatalytic performance of graphitic carbon nitride, optimized the band gap structure and enhanced the photogenerated carrier splitting. Consequently, the SCCN exhibits a remarkable photocatalytic H2 evolution rate of 4868 μmol/(g·h). This work demonstrates the potential of multi-nonmetal doped g-C3N4 as the ideal photocatalyst for H2 evolution.

  • RESEARCH ARTICLE
    Chen YANG, Xin-Yu MU
    Frontiers in Energy, 2023, 17(6): 822-832. https://doi.org/10.1007/s11708-023-0900-x

    Advancing portable electronics and electric vehicles is heavily dependent on the cutting-edge lithium-ion (Li-ion) battery technology, which is closely linked to the properties of cathode materials. Identifying trends and prospects of cathode materials based on patent analysis is considered a kernel to optimize and refine battery related markets. In this paper, a patent analysis is performed on 6 popular cathode materials by comprehensively considering performance comparison, development trend, annual installed capacity, technology life cycle, and distribution among regions and patent assignees. In the technology life cycle, the cathode materials majorly used in electric vehicle have entered maturity stage, while the lithium cobalt oxide (LCO) cathode that is widely used in portable electronics is still in the growth stage. In global patent distributions, China holds more than 50% of total patents. In the top 10 patent assignees of 6 cathode materials, 2 institutes are from China with the rest being Japan (6) and Republic of Korea (2), indicating that the technology of cathode materials in China is relatively scattered while cathode research is highly concentrated in Japan and Republic of Korea. Moreover, the patent distribution has to consider practical issues as well as the impacts of core patents. For example, the high cost discourages the intention of applying international patents. This paper is expected to stimulate battery research, understand technical layout of various countries, and probably forecast innovative technology breakthroughs.

  • RESEARCH ARTICLE
    Zhouzhou WANG, Qingwei WU, Jieming WANG, Ying YU
    Frontiers in Energy, 2024, 18(1): 89-100. https://doi.org/10.1007/s11708-023-0893-5

    Hydrogen production from photoelectrochemical (PEC) water splitting has been regarded as a promising way to utilize renewable and endless solar energy. However, semiconductor film grown on photoelectrode suffers from numerous challenges, leading to the poor PEC performance. Herein, a straightforward sol-gel method with the ligand-induced growth strategy was employed to obtain dense and homogeneous copper bismuthate photocathodes for PEC hydrogen evolution reaction. By various characterizations, it was found that the nucleation and surface growth of CuBi2O4 layer induced by 2-methoxyethanol ligand (2-CuBi2O4) demonstrated a decent crystallinity and coverage, as well as a large grain size and a low oxygen vacancy concentration, leading to the good ability of light absorption and carrier migration. Consequently, under simulated sunlight irradiation (AM1.5G, 100 mW/cm2), the 2-CuBi2O4 photocathode achieved an enhanced photocurrent density of −1.34 mA·cm−2 at 0.4 V versus the reversible hydrogen electrode and a promising applied bias photon-to-current efficiency of 0.586%. This surface modification by ligand growth strategy will shed light on the future design of advanced photoelectrodes for PEC water splitting.

  • RESEARCH ARTICLE
    Chunyu LI, Haihong WU, Ziyu CEN, Wanying HAN, Xinrui ZHENG, Jianxin ZHAI, Jiao XU, Longfei LIN, Mingyuan HE, Buxing HAN
    Frontiers in Energy, 2023, 17(6): 763-774. https://doi.org/10.1007/s11708-023-0897-1

    Plastic waste is causing serious environmental problems. Developing efficient, cheap and stable catalytic routes to convert plastic waste into valuable products is of great importance for sustainable development, but remains to be a challenging task. Zeolites are cheap and stable, but they are usually not efficient for plastic conversion at a low temperature. Herein a series of microporous and mesoporous zeolites were used to study the influence of porosity and acidity of zeolite on catalytic activity for plastics conversion. It was observed that H-Beta zeolite was an efficient catalyst for cracking high-density polyethylene to gasoline at 240 °C, and the products were almost C4–C12 alkanes. The effect of porosity and acidity on catalytic performance of zeolites was evaluated, which clearly visualized the good performance of H-Beta due to high surface area, large channel system, large amount accessible acidic sites. This study provides very useful information for designing zeolites for efficient conversion of plastics.

  • REVIEW ARTICLE
    Yongting ZHANG, Wanzhong LI, Hui GONG, Qianqian ZHANG, Liang YAN, Hao WANG
    Frontiers in Energy, 2024, 18(2): 160-186. https://doi.org/10.1007/s11708-024-0927-7

    Great progress has been made in the electrochromic (EC) technology with potential applications in various fields. As one of the most promising EC materials, Prussian blue (PB) has attracted great attention due to its excellent EC performance, such as low cost, easy synthesis, rich color states, chemical stability, suitable redox potential, and fast color-switching kinetics. This review summarizes the recent progress in PB electrodes and devices, including several typical preparation techniques of PB electrodes, as well as the recent key strategies for enhancing EC performance of PB electrodes. Specifically, PB-based electrochromic devices (ECDs) have been widely used in various fields, such as smart windows, electrochromic energy storage devices (EESDs), wearable electronics, smart displays, military camouflage, and other fields. Several opportunities and obstacles are suggested for advancing the development of PB-based ECDs. This comprehensive review is expected to offer valuable insights for the design and fabrication of sophisticated PB-based ECDs, enabling their practical integration into real-world applications.

  • MINI REVIEW
    Yichen Zhou, Jia Wen, Yulin Zheng, Wei Yang, Yuru Zhang, Wenxing Cheng
    Frontiers in Energy, 2024, 18(5): 685-698. https://doi.org/10.1007/s11708-024-0923-y

    As a clean and efficient renewable energy source, solar energy has been rapidly applied worldwide. The growth rate of China’s installed capacity ranks first in the world. However, the life span of photovoltaic (PV) modules is 25 to 30 years, and the rapid development of installed capacity indicates that a large number of PV modules will be decommissioned in the future. Therefore, the ongoing treatment of the scrapped PV waste cells in the near future requires urgent plans and countermeasures. Proper recycling and disposal of decommissioned PV modules is a practical requirement for the sustainable development of the country and industry. Crystalline silicon (c-Si) solar cells currently occupy 85%–90% of the market share, and some scholars have begun to seek the utilization pathways of the waste Si in and outside the PV industry. In this paper, the research status of the separation and recycling process of crystalline Si PV modules is reviewed, and the recycling ways of crystalline silicon are particularly focused on. In addition, the current bottlenecks in the PV recycling industry in China are analyzed and some suggestions on the sustainable development of the PV industry are proposed.

  • RESEARCH ARTICLE
    Guangxun CHEN, Jian-hua ZHANG, Kai-Ling ZHOU, Yang YANG, Haoxiang MA, Yuhong JIN, Jingbin LIU, Hao WANG
    Frontiers in Energy, 2024, 18(3): 369-377. https://doi.org/10.1007/s11708-024-0925-9

    Using the electrochemical technology to split water molecules to produce hydrogen is the key to obtain green hydrogen for solving the energy crisis. The large-scale application of hydrogen evolution reaction (HER) in water dissociation requires a highly active catalyst. In this paper, the highly dispersed PtCo bimetallic nanoparticles loading on MXene (PtCo/MXene) were prepared by using a step-to-step reduction strategy. The mentioned PtCo/MXene catalyst exhibits a high current density of −100 mA/cm2 in an acidic medium with just a 152 mV overpotential. In addition, the PtCo/MXene catalyst also displays a superior stability. Computational analysis and experimental testing demonstrate that the electronic interaction between Pt and Co can effectively modify the electronic structure of the active site, thereby enhancing the inherent catalytic performance of the material. More importantly, MXene two-dimensional nanosheets can expose more active sites because of their large specific surface area. Furthermore, MXene substrate with excellent electrical conductivity and harmonious interfaces between PtCo and MXene enhance charge transfer efficiency and lower the reaction activation energy.

  • RESEARCH ARTICLE
    Junwen CAO, Yun ZHENG, Wenqiang ZHANG, Bo YU
    Frontiers in Energy, 2024, 18(3): 390-398. https://doi.org/10.1007/s11708-023-0901-9

    Interconnector is a critical component to construct solid oxide cells (SOCs) stack. Oxidation of metallic interconnectors and Cr poisoning caused by oxidation are important factors that lead to long-term performance degradation of SOCs. Coating on the interconnector surface is an important approach to inhibit the oxidation and Cr migration of the interconnector. Herein, (La0.75Sr0.25)0.95MnO3–δ (LSM) and Mn1.5Co1.5O4 (MCO) are used to fabricate the coatings of interconnector. Two advanced thermal spray technology, atmospheric plasma spraying (APS) and low-pressure plasma spray (LPPS), are adopted for the coating preparation. The electrochemical performance, rising and cooling cycle stability, and Cr diffusion inhibition performance of the coatings are tested and evaluated. The result indicates that MCO can generate more uniform and denser coatings than LSM. In addition, MCO coatings prepared by LPPS shows the best electrochemical performance, rising and cooling cycle stability, and Cr diffusion inhibition. The initial area specific resistance (ASR) is 0.0027 Ω·cm2 at 800 °C. After 4 cooling cycle tests, the ASR increases to 0.0032 Ω·cm2 but lower than other samples. Meanwhile, the relative intense of Cr at the interface of SUS430 with MCO coatings fabricated by LPPS is lower than that of MCO fabricated by APS after 4 rising and cooling cycle operations, showing more favorable Cr diffusion inhibition performance.

  • RESEARCH ARTICLE
    Linsong GAN, Fei LIU, Xinhai YUAN, Lijun FU, Yuping WU
    Frontiers in Energy, 2023, 17(6): 775-781. https://doi.org/10.1007/s11708-023-0902-8

    Aqueous zinc-ion batteries (ZIBs) have great prospects for widespread application in massive scale energy storage. By virtue of the multivalent state, open frame structure and high theoretical specific capacity, vanadium (V)-based compounds are a kind of the most developmental potential cathode materials for ZIBs. However, the slow kinetics caused by low conductivity and the capacity degradation caused by material dissolution still need to be addressed for large-scale applications. Therefore, sodium vanadate Na2V6O16·3H2O (NVO) was chosen as a model material, and was modified with alumina coating through simple mixing and stirring methods. After Al2O3 coating modification, the rate capability and long-cycle stability of Zn//NVO@Al2O3 battery have been significantly improved. The discharge specific capacity of NVO@Al2O3 reach up to 228 mAh/g (at 4 A/g), with a capacity reservation rate of approximately 68% after 1000 cycles, and the Coulombic efficiency (CE) is close to 100%. As a comparison, the capacity reservation rate of Zn//NVO battery is only 27.7%. Its superior electrochemical performance is mainly attributed to the Al2O3 coating layer, which can increase zinc-ion conductivity of the material surface, and to some extent inhibit the dissolution of NVO, making the structure stable and improving the cyclic stability of the material. This paper offers new prospects for the development of cathode coating materials for ZIBs.

  • RESEARCH ARTICLE
    Zhiyuan WEI, Changying LIU, Xiaowen SUN, Yiduo LI, Haiyan LU
    Frontiers in Energy, 2024, 18(4): 447-462. https://doi.org/10.1007/s11708-023-0906-4

    Lithium-ion batteries (LIBs) are widely used in transportation, energy storage, and other fields. The prediction of the remaining useful life (RUL) of lithium batteries not only provides a reference for health management but also serves as a basis for assessing the residual value of the battery. In order to improve the prediction accuracy of the RUL of LIBs, a two-phase RUL early prediction method combining neural network and Gaussian process regression (GPR) is proposed. In the initial phase, the features related to the capacity degradation of LIBs are utilized to train the neural network model, which is used to predict the initial cycle lifetime of 124 LIBs. The Pearson coefficient’s two most significant characteristic factors and the predicted normalized lifetime form a 3D space. The Euclidean distance between the test dataset and each cell in the training dataset and validation dataset is calculated, and the shortest distance is considered to have a similar degradation pattern, which is used to determine the initial Dual Exponential Model (DEM). In the second phase, GPR uses the DEM as the initial parameter to predict each test set’s early RUL (ERUL). By testing four batteries under different working conditions, the RMSE of all capacity estimation is less than 1.2%, and the accuracy percentage (AP) of remaining life prediction is more than 98%. Experiments show that the method does not need human intervention and has high prediction accuracy.

  • RESEARCH ARTICLE
    Can FANG, Xiangmei TANG, Jiaoyan WANG, Qingfeng YI
    Frontiers in Energy, 2024, 18(1): 42-53. https://doi.org/10.1007/s11708-023-0913-5

    Highly efficient and stable iron electrodes are of great significant to the development of iron-air battery (IAB). In this paper, iron nanoparticle-encapsulated C–N composite (NanoFe@CN) was synthesized by pyrolysis using polyaniline as the C–N source. Electrochemical performance of the NanoFe@CN in different electrolytes (alkaline, neutral, and quasi-neutral) was investigated via cyclic voltammetry (CV). The IAB was assembled with NanoFe@CN as the anode and IrO2 + Pt/C as the cathode. The effects of different discharging/charging current densities and electrolytes on the battery performance were also studied. Neutral K2SO4 electrolyte can effectively suppress the passivation of iron electrode, and the battery showed a good cycling stability during 180 charging/discharging cycles. Compared to the pure nano-iron (NanoFe) battery, the NanoFe@CN battery has a more stable cycling stability either in KOH or NH4Cl + KCl electrolyte.

  • REVIEW ARTICLE
    Zeyu WANG, Yanru LIU, Shun CHEN, Yun ZHENG, Xiaogang FU, Yan ZHANG, Wanglei WANG
    Frontiers in Energy, 2024, 18(2): 241-262. https://doi.org/10.1007/s11708-024-0932-x

    Proton exchange membrane fuel cells (PEMFCs) are playing irreplaceable roles in the construction of the future sustainable energy system. However, the insufficient performance of platinum (Pt)-based electrocatalysts for oxygen reduction reaction (ORR) hinders the overall efficiency of PEMFCs. Engineering the surface strain of catalysts is considered an effective way to tune their electronic structures and therefore optimize catalytic behavior. In this paper, insights into strain engineering for improving Pt-based catalysts toward ORR are elaborated in detail. First, recent advances in understanding the strain effects on ORR catalysts are comprehensively discussed. Then, strain engineering methodologies for adjusting Pt-based catalysts are comprehensively discussed. Finally, further information on the various challenges and potential prospects for strain modulation of Pt-based catalysts is provided.

  • RESEARCH ARTICLE
    Cong LEI, Rongzhong YANG, Jianan ZHAO, Wenbin TANG, Fadong MIAO, Qinghong HUANG, Yuping WU
    Frontiers in Energy, 2024, 18(4): 436-446. https://doi.org/10.1007/s11708-024-0928-6

    In this study, the Lewis doping approach of polyaniline (PANI) was employed to fabricate cobait–nitrogen–carbon (Co–N–C) oxygen electrocatalysts for Zn–air batteries, aiming to enhance the active spots of Co–N–C. This resulting Co–N–C catalysts exhibited well-defined nanofiber networks, and the Brunauer-Emmett-Teller (BET) analysis confirmed their substantial specific surface area. Electrochemical experiments demonstrated that the Co–N–C catalysts achieved the half-wave potential (vs. RHE) of 0.85 V in alkaline medium, overcoming Pt/C and iron–nitrogen–carbon (Fe–N–C) counterparts in extended cycle testing with only a 25 mV change in a half-wave potential after 5000 cycles. Remarkably, the highest power density measured in the zinc (Zn)-air battery reached 227 mW/cm2, a significant improvement over the performance of 101 mW/cm2 of the platinum on activated carbon (Pt/C) catalyst. These findings highlight the advantageous stability enhancement associated with the utilization of Co in the Co–N–C catalysts.

  • RESEARCH ARTICLE
    Xiao GUO, Yanbo CHE, Zhihao ZHENG, Jiulong SUN
    Frontiers in Energy, 2024, 18(1): 28-41. https://doi.org/10.1007/s11708-023-0912-6

    With the promotion of “dual carbon” strategy, data center (DC) access to high-penetration renewable energy sources (RESs) has become a trend in the industry. However, the uncertainty of RES poses challenges to the safe and stable operation of DCs and power grids. In this paper, a multi-timescale optimal scheduling model is established for interconnected data centers (IDCs) based on model predictive control (MPC), including day-ahead optimization, intraday rolling optimization, and intraday real-time correction. The day-ahead optimization stage aims at the lowest operating cost, the rolling optimization stage aims at the lowest intraday economic cost, and the real-time correction aims at the lowest power fluctuation, eliminating the impact of prediction errors through coordinated multi-timescale optimization. The simulation results show that the economic loss is reduced by 19.6%, and the power fluctuation is decreased by 15.23%.