In order to solve the problems of high cost and low electrolytic efficiency of traditional catalysts and realize the development of large-scale green hydrogen production technology, an interfacial catalyst based on transition metal was constructed by structural design and synthesis optimization in this study. The Ni₃Se₂/NiSe@NF heterojunction bifunctional electrocatalyst with interface structure was prepared on a nickel foam (NF) substrate by a two-step hydrothermal method. The strong charge transfer at the heterogeneous interface of Ni₃Se₂/NiSe@NF effectively optimizes the electronic structure of Ni₃Se₂/NiSe@NF compared with the single interface (Ni₃Se₂@NF and NiSe@NF), thus increasing the activities of hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). The prepared Ni₃Se₂/NiSe@NF has an overpotential of 71 and 207 mV (10 mA·cm^-2) at 1 mol/L KOH, respectively, and has impressive stability (no significant degradation within 500 h). In addition, when the current density is 10 mA·cm^-2, the current of the monolithic water decomposition electrolyzer with Ni₃Se₂/NiSe@NF as anode and cathode can be reduced to 1.52 V. Therefore, this study provides a new idea for the development of low-cost and high-stability catalysts for water electrolysis, which is expected to accelerate the integration of green hydrogen preparation and renewable energy systems, and help realize the goal of “dual-carbon”.

Proton exchange membrane water electrolyzer decomposes water into oxygen and hydrogen using electrical energy as the driving force. During the water electrolysis process, the anode catalyst layer is a key factor influencing the performance of the electrolyzer. Based on the initial structural parameters of the proton exchange membrane water electrolyzer, this study establishes a one-dimensional electrolysis model to investigate the effect of ionomers in the anode catalyst layer on the operational performance of electrolyzer. Six ionomers with different equivalent weights, including both long-chain and short-chain types, were compared. Proton conductivity of ionomers was corrected based on their equivalent weights, and interfacial contact resistance at different ionomer contents was calculated using the constriction resistance theory. Since excessive ionomer in the catalyst layer can cover the active sites of catalyst, there exists an optimal ionomer content in the anode catalyst layer. When using different types of ionomers, the optimal ionomer content varies due to differences in water absorption, which is related to the porosity of the catalyst layer after ionomer water absorption and swelling. Based on this, a formula related to the optimal porosity is proposed in this paper. Furthermore, the performance of short-chain ionomer consistently outperforms that of long-chain ionomer both before and after water absorption and swelling, which demonstrates the advantages of short-chain ionomers. This study can provide references for the optimal design of catalyst layer in proton exchange membrane water electrolyzer.

Temperature significantly affects battery performance. However, the mechanism of in-plane temperature gradient caused by high current on battery degradation is still unclear. In this study, the in-plane temperature gradient is artificially constructed between battery tabs and bottom region. Then, the fast-charging cycling test is performed. Post-mortem analysis after battery cycling is carried out to obtain the anode surface morphology and elemental distribution. A three-dimensional electrochemical model is developed to obtain the internal parameter distributions during fast charging. The results indicate that the battery degradation process can be divided into three stages: in-plane current density gradient stage, in-plane temperature gradient stage, and emergence of degradation factors stage. A spatial matching criterion between in-plane temperature gradient and in-plane current density gradient is proposed to suppress battery degradation, where optimal performance is achieved when high current density region coincide with high temperature region. Specifically, the in-plane temperature gradient with high temperature at the high current density tabs and low temperature at the low current density bottom region enhances battery fast charging performance, maintaining over 90% capacity after 50 cycles at 2C charging rate. However, an in-plane temperature gradient in the opposite direction can lead to lithium plating and material cracking, with a 34.3% capacity loss after just 5 cycles. Additionally, the low-temperature discharge tests demonstrate that achieving the spatial matching criterion can enhance battery discharge performance. Specifically, the discharge capacity increases by 8% at −20 ​℃. This study provides a novel temperature-regulation-based approach for reducing battery polarization.