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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.

  • 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
    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
    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.

  • 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
    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
    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.

  • 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.

  • 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.

  • 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
    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
    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
    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%.

  • REVIEW ARTICLE
    Shun CHEN, Yanru LIU, Xiaogang FU, Wanglei WANG
    Frontiers in Energy, 2024, 18(3): 330-355. https://doi.org/10.1007/s11708-024-0929-5

    Exploring advanced platinum (Pt)-based electrocatalysts is vital for the widespread implementation of proton exchange membrane fuel cells (PEMFCs). Morphology control represents an effective strategy to optimize the behavior of Pt catalysts. In this work, an attempt is made to comprehensively review the effect of morphology control on the catalytic behavior of catalysts in the oxygen reduction reaction (ORR). First, the fundamental physicochemical changes behind morphology control, including exposing more active sites, generating appropriate lattice strains, and forming different crystalline surfaces, are highlighted. Then, recently developed strategies for tuning the morphologies of electrocatalysts, including core-shell structures, hollow structures, nanocages, nanowires, and nanosheets, are comprehensively summarized. Finally, an outlook on the future development of morphology control of Pt catalysts is presented, including rational design strategies, advanced in situ characterization techniques, novel artificial intelligence, and mechanical learning. This work is intended to provide valuable insights into designing the morphology and technological innovation of efficient redox electrocatalysts in fuel cells.

  • 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.

  • REVIEW ARTICLE
    Yanzhi Cai, Zhongyi Hu, Laifei Cheng, Siyu Guo, Tingting Liu, Shaohua Huang, Dengpeng Chen, Yuhan Wang, Haiming Yu, Yuan Zhou
    Frontiers in Energy, 2024, 18(5): 612-639. https://doi.org/10.1007/s11708-024-0911-2

    In recent years, the rapid development of portable/wearable electronics has created an urgent need for the development of flexible energy storage devices. Flexible lithium-ion batteries (FLIBs) have emerged as the most attractive and versatile flexible electronic storage devices available. Carbon nanotubes (CNTs) are hollow-structured tubular nanomaterials with high electrical conductivity, large specific surface area, and excellent mechanical properties. Graphene (G) is to some extent comparable to CNTs, because both have unlimited value in flexible electrodes. Herein, a systematic summary of the application of CNT and G in FLIBs electrodes is presented, including different functional applications and services at different temperatures. Furthermore, the effects of electrode structures, including powder, wire-shaped, and film-shaped structures, on electrochemical properties is highlighted. The assembly structures of the FLIBs consisting of CNT and G-based flexible electrodes to realize different functions, including bendability, stretchability, foldability, self-healing, and self-detecting, are systematically reviewed. The current challenges and development prospects of flexible CNT and G-based flexible electrodes and corresponding FLIBs are discussed.

  • RESEARCH ARTICLE
    Chengrong YU, Zehua PAN, Hongying ZHANG, Bin CHEN, Wanbing GUAN, Bin MIAO, Siew Hwa CHAN, Zheng ZHONG, Yexin ZHOU
    Frontiers in Energy, 2024, 18(3): 356-368. https://doi.org/10.1007/s11708-023-0919-z

    Due to the depletion of traditional fossil fuels and the aggravation of related environmental problems, hydrogen energy is gaining more attention all over the world. Solid oxide fuel cell (SOFC) is a promising power generation technology operating on hydrogen with a high efficiency. To further boost the power output of a single cell and thus a single stack, increasing the cell area is an effective route. However, it was recently found that further increasing the effective area of an SOFC single cell with a flat-tubular structure and symmetric double-sided cathodes would result in a lower areal performance. In this work, a multi-physical model is built to study the effect of the effective area on the cell performance. The distribution of different physical fields is systematically analyzed. Optimization of the cell performance is also pursued by systematically tuning the cell operating condition and the current collection setup. An improvement of 42% is revealed by modifying the inlet gas flow rates and by enhancing the current collection. In the future, optimization of cell geometry will be performed to improve the homogeneity of different physical fields and thus to improve the stability of the cell.

  • MINI REVIEW
    Jai PRAKASH, Zhangsen CHEN, Shakshi SAINI, Gaixia ZHANG, Shuhui SUN
    Frontiers in Energy, 2024, 18(2): 187-205. https://doi.org/10.1007/s11708-024-0939-3

    Due to its fascinating and tunable optoelectronic properties, semiconductor nanomaterials are the best choices for multidisciplinary applications. Particularly, the use of semiconductor photocatalysts is one of the promising ways to harness solar energy for useful applications in the field of energy and environment. In recent years, metal oxide-based tailored semiconductor photocatalysts have extensively been used for photocatalytic conversion of carbon dioxide (CO2) into fuels and other useful products utilizing solar energy. This is very significant not only from renewable energy consumption but also from reducing global warming point of view. Such current research activities are promising for a better future of society. The present mini-review is focused on recent developments (2–3 years) in metal oxide semiconductor hybrid photocatalysts-based photo-electrochemical conversion of CO2 into fuels and other useful products. First, general mechanism of photo-electrochemical conversion of CO2 into fuels or other useful products has been discussed. Then, various metal oxide-based emerging hybrid photocatalysts including tailoring of their morphological, compositional, and optoelectronic properties have been discussed with emphasis on their role in enhancing photo-electrochemical efficienty. Afterwards, mechanism of their photo-electrochemical reactions and applications in CO2 conversion into fuels/other useful products have been discussed. Finally, challenges and future prospects have been discussed followed by a summary.

  • MINI REVIEW
    Meng FANG, Yuqin PENG, Puwei WU, Huan WANG, Lixin XING, Ning WANG, Chunmei TANG, Ling MENG, Yuekuan ZHOU, Lei DU, Siyu YE
    Frontiers in Energy, 2024, 18(3): 308-329. https://doi.org/10.1007/s11708-024-0916-x

    The development of renewable and affordable energy is crucial for building a sustainable society. In this context, establishing a sustainable infrastructure for renewable energy requires the integration of energy storage, specifically use of renewable hydrogen. The hydrogen evolution reaction (HER) of electrochemical water splitting is a promising method for producing green hydrogen. Recently, two-dimensional nanomaterials have shown great promise in promoting the HER in terms of both fundamental research and practical applications due to their high specific surface areas and tunable electronic properties. Among them, molybdenum disulfide (MoS2), a non-noble metal catalyst, has emerged as a promising alternative to replace expensive platinum-based catalysts for the HER because MoS2 has a high inherent activity, low cost, and abundant reserves. At present, greatly improved activity and stability are urgently needed for MoS2 to enable wide deployment of water electrolysis devices. In this regard, efficient strategies for precisely modifying MoS2 are of interest. Herein, the progress made with MoS2 as an HER catalyst is reviewed, with a focus on modification strategies, including phase engineering, morphology design, defect engineering, heteroatom doping, and heterostructure construction. It is believed that these strategies will be helpful in designing and developing high-performance and low-cost MoS2-based catalysts by lowering the charge transfer barrier, increasing the active site density, and optimizing the surface hydrophilicity. In addition, the challenges of MoS2 electrocatalysts and perspectives for future research and development of these catalysts are discussed.

  • RESEARCH ARTICLE
    Brian Lenhart, Devadharshini Kathan, Valerie Hiemer, Mike Zuraw, Matt Hull, William E. Mustain
    Frontiers in Energy, 2024, 18(5): 650-664. https://doi.org/10.1007/s11708-024-0904-1

    In modern alkaline batteries, the zinc anode is the performance-limiting and lifetime-limiting electrode, making the choice of zinc powder critical. Due to the various material fabrication processes that are used to manufacture industrial zinc powder, there exists a wide array of possible zinc particle shapes, sizes, and crystallinities. These industrial zinc powders are typically conceived, produced, and tested through trial-and-error processes using historical “rules of thumb.” However, a data-driven approach could more effectively elucidate the optimum combination of zinc particle properties. In this paper, the effect of Zn particle size, shape, and crystallinity on the achievable capacity and corrosion current is investigated. The Zn types are tested in both powder and slurry form. Following the data collection, a factorial-based statistical analysis is performed to determine the most statistically significant variables affecting capacity and corrosion. This information is then used to down-select to a subset of particles that are tested in cylindrical cells with an AA-equivalent geometry. The reported technique can be used to develop actionable principles for battery manufacturers to create cells that are more stable, longer lasting, and have higher energy densities.

  • PERSPECTIVES
    Ziyuan TENG, Chao TAN, Peiyuan LIU, Minfang HAN
    Frontiers in Energy, 2024, 18(1): 16-27. https://doi.org/10.1007/s11708-023-0909-1

    The hydrogen fuel cell vehicle is rapidly developing in China for carbon reduction and neutrality. This paper evaluated the life-cycle cost and carbon emission of hydrogen energy via lots of field surveys, including hydrogen production and packing in chlor-alkali plants, transport by tube trailers, storage and refueling in hydrogen refueling stations (HRSs), and application for use in two different cities. It also conducted a comparative study for battery electric vehicles (BEVs) and internal combustion engine vehicles (ICEVs). The result indicates that hydrogen fuel cell vehicle (FCV) has the best environmental performance but the highest energy cost. However, a sufficient hydrogen supply can significantly reduce the carbon intensity and FCV energy cost of the current system. The carbon emission for FCV application has the potential to decrease by 73.1% in City A and 43.8% in City B. It only takes 11.0%–20.1% of the BEV emission and 8.2%–9.8% of the ICEV emission. The cost of FCV driving can be reduced by 39.1% in City A. Further improvement can be obtained with an economical and “greener” hydrogen production pathway.