Understanding the catalytic mechanism of non-noble transition metal electrocatalysts is crucial to design-ing high-efficiency,low-cost,and durable alternative electrocatalysts for water splitting which comprises the hydrogen evolution reaction(HER)and oxygen evolution reaction(OER).In this work,Se-NiSe2 hybrid nanosheets with a self-regulated ratio of ionic Se(I-Se)to elemental Se(E-Se)are designed on carbon cloth by solution synthesis and hydrothermal processing.The effects of the I-Se/E-Se ratios on the elec-trocatalytic characteristics in HER and OER are investigated systematically both experimentally and the-oretically.The optimized bifunctional electrocatalyst needs overpotentials of only 133 mV to deliver an HER current density of 10 mA cm-2 and 350 mV to generate an OER current density of 100 mA cm-2 in 1.0 mol L-1 KOH.Based on the density-functional theory calculation,surface-adsorbed E-Se is beneficial to optimizing the electron environment and the adsorption/desorption free energy of hydrogen/water of the hybrid catalyst,consequently facilitating the electrocatalytic water splitting process.There is a proper I-Se/E-Se ratio to improve the catalytic activity and kinetics of the reaction and the optimized E-Se ad-sorption amount can balance the interactions between I-Se and E-Se,so that the catalyst can achieve appropriate Se-H binding and active site exposure for the excellent electrocatalytic activity.To demon-strate the practicality,the assembled symmetrical device can be powered by an AA battery to produce hydrogen and oxygen synchronously.Our results provide a deeper understanding of the catalytic mech-anism of transition metal selenides in water splitting and insights into the design of high-efficiency and low-cost electrocatalysts in energy-related applications.

Hubei Key Laboratory of Plasma Chemistry and Advanced Materials,Hubei Engineering Technology Research Center of Optoelectronic and New Energy Materials,Wuhan Institute of Technology,Wuhan 430205,China;Department of Physics,Department of Materials Science and Engineering,Department of Biomedical Engineering,City University of Hong Kong,Tat Chee Avenue,Kowloon,Hong Kong,China;School of Textile Science and Engineering,Xi'an Polytechnic University,Xi'an 710048,China;State Key Laboratory of Refractories and Metallurgy,Institute of Advanced Materials and Nanotechnology,Wuhan University of Science and Technology,Wuhan 430081,China;Department of Chemistry,Key Laboratory for Preparation and Application of Ordered Structural Materials of Guangdong Province,Shantou University,Shantou 515063,China

[1]Xiang Peng;Yujiao Yan;Shijian Xiong;Yaping Miao;Jing Wen;Zhitian Liu;Biao Gao;Liangsheng Hu;Paul K.Chu-.Se-NiSe2 hybrid nanosheet arrays with self-regulated elemental Se for efficient alkaline water splitting)[J].材料科学技术（英文版）,2022(23):136-143

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