Design,Synthesis,and Electrocatalytic Properties Of Nickel-Based Electrocatalysts Towards Water Electrolysis For Hydrogen Production

In order to deal with the energy crisis caused by the overuse of fossil fuels and the associated environmental problems,the development of clean and efficient renewable energy sources is particularly important.As an ideal energy carrier,hydrogen is expected to occupy an important position in the new energy structure in the future.Water electrolysis technology coupled with renewable energy is a sustainable way to produce hydrogen,but its industrial application is limited by high energy consumption cathodic hydrogen evolution（HER）and anodic oxygen evolution reaction（OER）.On the other hand,the hydrazine-assisted overall water electrolyzer system（OHz S）uses hydrazine oxidation reaction（Hz OR）with lower thermodynamic potential to replace the traditional OER reaction,which can break the high voltage barrier of traditional electrolytic water and realize energy-saving electrolysis to produce hydrogen.At present,the precious metals Pt and Ru O₂ are the most efficient HER and Hz OR electrocatalysts respectively,but the high cost and rare reserves severely limit their large-scale industrial applications.Therefore,it is of great significance to develop low-cost,high-performance,and long-life transition metal-based HER and Hz OR electrocatalysts.In this paper,the transition metal nickel and tungsten nitride are the main research objects,focusing on the design and preparation of highly active and stable electrocatalysts used in alkaline HER and Hz OR processes,as well as the correlation between the composition-structure-catalytic performance of electrocatalysts.The main research progress is as follows:（1）A nickel-foamed carbon-coated boron-doped metal nickel nanosheet electrocatalyst（Ni-B@C）was prepared by simple hydrothermal,room temperature borization,and subsequent annealing methods.Density functional theory calculations（DFT）show that B-doped induces the electron redistribution of Ni,optimizing H₂O dissociation step and the composite desorbed step of hydrogen intermediate（H*）,thereby significantly improving the alkaline HER dynamics;the construction of graded nanosheets is conducive to the exposure of the active site,and the resulting catalyst has a high electrochemical activity area.Based on the above factors,the Ni-B@C electrocatalyst exhibits excellent HER activity and stability in alkaline media.The Ni-B@C electrocatalyst only needs a low overpotential of 26 m V to drive a current density of 10 m A·cm^-2,and no significant performance degradation occurred in the 10,50,and 100m A·cm^-2 current density small constant current test for 50 h.This work can provide a certain reference for the reasonable design of efficient and low-cost transition metal electrocatalysts.（2）A WN/Ni heterostructure electrocatalyst loaded with nickel foam（NF）was designed and synthesized by combining hydrothermal and nitriding annealing treatment methods.The experimental and DFT calculation results show that the construction of metal nitride/metal heterostructure effectively triggers the charge transfer between the two phases,improves the charge transfer rate,and optimizes the absorption/desorption of intermediates in the HER and Hz OR processes,thereby effectively enhancing the intrinsic catalytic activity of the catalyst.The resulting catalyst therefore exhibits excellent HER and Hz OR catalytic activity in alkaline solution.In 1.0 M KOH,the hydrogenation overpotential of the WN/Ni/NF electrode at 10 m A·cm^-2 is only 28 m V.At the same time,in the 1.0 M KOH/0.4 M N₂H₄ electrolyte,driving the current density of 10 m A·cm^-2 requires only an ultra-low potential of-26 m V.The two-electrode hydrazine oxidation-assisted hydrogen analysis system assembled with WN/Ni/NF also exhibits excellent low-voltage hydrogen production characteristics,and the battery voltage required to reach a current density of 100m A·cm^-2 is 348 m V.This work verifies the feasibility of interface engineering for constructing catalysts and provides a certain reference for the design and synthesis of high-efficiency,high-stability,and low-cost dual-function electrocatalysts.