Construction Of Element-doped Non-precious Metal Nanostructure Array Catalysts And Their Electrocatalytic Water Splitting Performance

The large consumption of non-renewable resources has exacerbated environmental pollution and the greenhouse effect,and it is becoming more and more urgent to use renewable clean energy to replace traditional fossil energy.However,both solar and wind energy are intermittent energy sources that cannot be sustained for a long time.The increase in demand for energy motivates the development of new materials and technologies that enable the transformation of H₂O into sustainable H₂fuel.The electrolysis of water is considered as a promising route for high-purity hydrogen supply.As we all know,noble metals have high electrocatalytic performance,but their application is greatly restricted due to their severe scarcity and high price.Therefore,it is of great significance to search for non-precious metal electrocatalysts with low price and superior performance.Transition metals are cheap and easy to obtain,and have unique electronic structures and strong redox ability,which makes them widely used in electrocatalytic water splitting.In this thesis,transition metals are used as the research object,using doping and vacancy strategies to design and prepare metal sulfides,selenides,phosphides non-noble metal electrocatalysts.The prepared catalyst was analyzed by XRD,XPS,SEM,TEM,HRTEM and other characterization methods to analyze its material structure and microscopic morphology.The electrocatalytic hydrogen evolution reaction（HER）or oxygen evolution reaction（OER）activity and stability of the catalyst were investigated,and the electrocatalytic mechanism was clarified and its practical application value was evaluated.The main contents are as follows:1.Mn-N-Co₉S₈ nanorod array electrocatalyst was successfully prepared on foam nickel by hydrothermal and calcination method,the performance of the catalyst was optimized by controlling the doping amount of Mn and N.In alkaline conditions,the best Mn/N co-doped Co₉S₈（Mn-N-Co₉S₈）catalyst can achieve overpotential of 102and 238 m V at-10 and-100 m A cm^-2 in 1 M KOH solution,respectively,which is significantly better than Mn-Co₉S₈,N-Co₉S₈ and the Co₉S₈-based HER catalysts reported in recent years,and the Mn-N-Co₉S₈ has an excellent stability.The higher HER catalytic performance of Mn-N-Co₉S₈ benefits from the dopants optimizing the electronic structure of the catalyst,lowering the water dissociation energy barrier,and accelerating the electron transport rate,thereby enhancing the inherent HER activity of the active site.2.Using the 3D porous NF-supported Co-MOF triangular nanosheet array as the precursor,the Fe-N-Co Se₂ nanosheet array was prepared by static and calcination methods.In alkaline conditions,the Fe-N-Co Se₂ TNA obtained has a low overpotential of 270 m V at 50 m A cm^-2,showing excellent OER performance.The long-term durability of 100 m A cm^-2 constant current up to 100 h is superior to reported transition metal catalysts and commercial Ru O₂ catalysts.The research results of the catalytic mechanism show that Fe doping enhances the specific surface area（ECSA）and the number of active sites of the material,thereby promoting the improvement of OER activity.N doping reduces the charge transfer resistance,promotes charge transfer and accelerates the reaction kinetics,thereby synergistically increasing the OER activity of the catalyst.3.The Cr_0.4Co₂P（V_p）NWs electrocatalyst was successfully prepared on foam nickel by hydrothermal and calcination methods.The obtained Cr_0.4Co₂P（V_p）NWs catalyst has excellent bifunctional catalytic activity for both HER and OER,and the overpotentials at-10 m A cm^-2 and 20 m A cm^-2 are 37 and 253 m V,respectively.The Cr_0.4Co₂P（V_p）NWs dual-function catalytic electrode only needs a voltage of 1.54 V to provide 10 m A cm^-2.The research results of the catalytic mechanism show that the formation of a large number of vacancy defects on the surface of Co₂P nanowires may effectively reduce the energy barrier of H₂O adsorption and optimize the adsorption energy of HER and OER intermediates.In addition,the Cr_0.4Co₂P（V_p）NWs nanowire array on the foamed nickel has a high electrochemically active area,which is conducive to charge and electrolyte mass transfer,thereby further enhancing the electrocatalytic activity.