Study On The Controllable Synthesis And Catalytic Performance Of Nickel-Cobalt-Based Bimetal Derivatives

In recent years,environmental pollution has become more and more serious due to the burning of fossil energy,and the development of clean,pollution-free and highly efficient renewable energy has become urgent.The electrocatalytic decomposition of water to produce hydrogen,due to its high efficiency,high purity gas production,environmental friendliness and strong adaptability to energy fluctuations,shows excellent application prospects in hydrogen energy development technology.Nowadays,precious metals such as platinum,ruthenium or platinum-based precious metals exhibit extremely excellent electrocatalytic properties due to their excellent lattice structure.However,it is well known that precious metals have low abundance on the earth,small storage capacity and relatively high cost.High,not suitable for large-scale applications.Therefore,in order to solve this problem,the development and exploration of a non-noble metal electrocatalyst with stable performance,high efficiency and economical practicality is put on the agenda.Among many non-precious metal electrocatalysts,transition metal phosphides have become popular materials in the field of electrocatalysis due to their unique electronic properties,stable structure,high electronic conductivity and good chemical stability.A single transition metal electrocatalyst,due to its higher surface energy barrier,causes its hydrogen production efficiency to be low.Compared with a single transition metal phosphide,two or more transition metal phosphides are selected to use the synergistic effect between their metals.The electronic structure can be optimized,the charge transfer rate can be accelerated,and the tissue morphology can be adjusted to increase the reactive sites,thereby improving the stability and catalytic activity of the catalyst.This thesis mainly studies the application of nickel and cobalt bimetallic phosphides in electrocatalysis.Three electrocatalysts with different structures and morphologies have been synthesized through different research methods such as adjusting the ratio and doping of non-metallic elements.The specific research content is as follows:（1）N i Co-LDH precursor is obtained by hydrothermal reaction,and N ix Coy P in different proportions is obtained by low-temperature phosphating method.The obtained phosphide has a three-dimensional sea urchin-like structure and basically maintains the three-dimensional morphology of the precursor.The space structure formed by the overlapping nanorods makes it have a larger specific surface area and reactive sites,which is beneficial to the occurrence of e lectrochemical reactions.A comparative analysis of the electrochemical test results of different ratios of N ix Coy P shows that N i Co_1.5P@NF and Ni₂Co P@NF show better HER（123m V）and OER（253m V）performance at a current density of 10m Acm^-2.（2）The synthesis of nickel-cobalt bimetallic phosphide on different substrates was explored,and on this basis,the electrocatalytic performance was improved by nitrogen doping.A new type of nitrogen doping method is proposed.Through the CVD method,urea is pyrolyzed.According to subsequent characterization methods,it is known that nitrogen doping has been successfully achieved.According to electrochemical tests,N-Ni Co P@NF has the most excellent electrocatalytic performance,and its high aspect ratio nano-needle clusters made of nano-flowers make its specific surface area larger,thus increasing more reactions.The active site,the shorter transmission distance accelerates the transfer rate of the charge,so that the electrochemical performance is good.When the cur rent density is 10m A cm^-2,the overpotential of the hydrogen evolution reaction of N-Ni Co P@NF is 75m V.After5000 cycles of CV,the polarization curve before and after the comparison does not show obvious attenuation,showing good stability.（3）With the special morphology of similar Prussian blue,N i Co-LDH is prepared based on the one-step hydrothermal method,using potassium cobalt cyanide as the precursor,two-step hydrothermal synthesis of the new nanocube-shaped N i Co-LDH@PBA,Ni Co P@PBA was successfully prepared through low-temperature phosphating reaction,and the original morphology was basically maintained after phosphating.Among them,N i Co P@PBA shows the best catalytic effect in both hydrogen evolution reaction and oxygen evolution reaction performance.When the current density is 10m A cm^-2,59m V(corresponding to the Tafel slope of 54 m V dec^-1)and 263m V are required respectively.(Corresponding to the Tafel slope of 120m V dec^-1)overpotential can break the reaction energy barrier,is a relatively excellent dual-function catalyst.The stability test shows that the Ni Co P@PBA electrode has good stability,and there is no obvious attenuation after running for 90000s.