Preparation Of Nickel-based Nitride Composite Catalyst And Its High Efficiency In Water Electrolysis

The development of clean renewable new energy to replace the traditional fossil energy technology is the only way to achieve social sustainable development.China is the world’s largest emitter of carbon dioxide emissions and faces a daunting task of reducing emissions.At present,it is urgent to develop clean energy when the development goal of carbon peak and carbon neutral is put forward.Hydrogen energy is a green,clean,high energy and efficient energy,and its development and utilization is the trend of clean energy.The original intention of develop hydrogen is to realize zero or low carbon emissions,and the vast majority of hydrogen is still produced from non-renewable sources such as coal and natural gas.However,only hydrogen from renewable sources can be truly sustainable.Therefore,the development of green hydrogen（electrolysis of water）is a direction of future energy development.Water electrolysis is an electrochemical process in which oxygen and hydrogen are separated at the anode and cathode under the action of direct current.However,the existence of overpotential caused by anode,cathode and other factors seriously restricts the efficiency of hydrogen production from electrolytic water.In order to reduce energy consumption and realize large-scale application of water electrolysis technology,it is necessary to develop green,efficient and cheap catalysts to improve the efficiency of hydrogen production.Nickel-based catalysts are widely used in alkaline electrolysis of water for hydrogen production due to their rich,cheap and efficient electrocatalysis of HER activity.However,due to the strong adsorption of nickel to hydrogen,the catalytic activity of nickel-based catalyst is limited,which makes it fail to meet the requirements of commercialization.As a heterogeneous catalyst,the surface structure of water electrolysis catalyst directly affects the performance of electrocatalysis.Based on this,the surface structure of nickel-based nitride composite catalyst is studied in this paper to achieve high activity electrolysis water decomposition.The research results of this paper are as follows:（1）Ni/VN catalysts supported by metal nitrides are synthesized and the electrocatalytic activity of HER is tested.The results show that the pure nickel nanoparticles are about 20 nm.After the addition of transition metal nitride,the nickel nanoparticles of metal-supported catalyst are obviously dispersed,and the particle size is 7～8nm.During electrocatalytic HER reaction,metal-supported catalysts can expose more active sites of nickel.In addition,the addition of metal nitride carrier reduces the electron cloud density of nickel,which is conducive to improving the catalytic process of HER reaction by the active center of metal nickel.（2）A heterojunction catalyst is synthesized for the compound of nitride（Fe Ni₃N）and sulfide（Ni₃S₂）.The electronic effect between Fe Ni₃N and Ni₃S₂ enhanced the intrinsic activity of the composite catalyst.In addition,density functional theory（DFT）study confirmed that Fe Ni₃N-Ni₃S₂ reduced the Gibbs free energy of the reaction intermediates during OER reaction（promoted the adsorption of hydroxyl species,electrochemical oxidation,peroxide intermediates and oxygen generation step）.The test of zinc empty battery shows that the catalyst has low charging voltage and long cycle performance.（3）A heterojunction catalyst is synthesized by the combination of nitride（Fe Ni₃N）and metal alloy（Fe Ni₃）.The existence of the heterostructure provided abundant activity sites for HER（Fe-Ni-Ni and Ni-Ni-Ni vacancy）,thus enhancing the activity of HER;At the same time,the catalyst with this structure increased the electrochemical active area of OER and the number of active sites.In addition,the current density is 10 m A cm^-2 and only 1.50V voltage is required when the dual-function catalyst is self-assembled into a symmetric electrode for full hydrolysis test.（4）A kind of supported catalyst with metal nitride（Ni₃N）and oxide（V₂O₃）composite is synthesized.The interaction between Ni₃N and V₂O₃ leads to electron transfer from Ni₃N to V₂O₃,which reduces the electron cloud density around nickel and thus improves HER electrocatalytic activity.The anodic 5-（hydroxymethyl）furfural oxidation reaction（Hmf OR）is tested and it is found that only 230 m V is required for the overpotential at the current density of 10 m A cm^-2.When HER and Hmf OR are coupled to prepare a symmetrical membraneless electrolytic cell device for testing,he hydrogen generation voltage is only 1.40 V at the current density is 10 m A cm^-2.We believe that this concept is of great significance in the field of electrocatalytic hydrogen evolution and can provide an important strategy for the development of composite catalysts.