Research On The Performance Control Of Transition Metal Electrocatalysts

It has been plagued people for a long time because of the low combustion efficiency and side effect of common fossil fuels,which will cause a great burden on the environment.Therefore,it is urgent to find clean energy sources which can be used as a substitute.Hydrogen,raw materials and products only produce water,is one of the most popular environmentally friendly energy with highcombustion calorific value.It is recognized as a clean energy that can replace fossil fuels.Water splitting has always been used to produce hydrogen by hydrogen evolution reaction so that electrocatalysts for water splitting with good performance is needed.However,the existing efficient catalysts is platinum（Pt）,palladium（Pd）,rhodium（Rh）,silver（Ag）and other precious metal-based catalysts that hinders the widespread application of water splitting in the industrial field because of its small reserves and high costs.Hence,it is the main research direction to search for high catalytic performance materials which can replace these noble metal catalysts.Transitional metals have gradually attracted people’s attention,such as cobalt（Co）,iron（Fe）,aluminum（Al）,have extremely rich reserves and excellent performance.At present,there are many methods that can optimize the performance of the catalyst to a certain extent.For example,the performance of the catalyst can be improved by adjusting the morphology of the material,element doping,surface modification,or changing the external field environment.This paper has done research on catalyst performance control from many aspects.The main experimental results are as follows:Firstly,the Co:FeS₂/CoS₂ material was prepared by one-step hydrothermal route with the morphology of nanoflower which could increase the surface area.After that,the material was qualitatively analyzed through a series of characterization means to verify the constituent elements and valence of the material.To reveal the relationship between the external environment and the catalytic performance of the Co:Fe S₂/Co S₂,the materials was studied from two aspect.The former part mainly tests the effect of external temperature on the catalytic performance of the catalyst.When the temperature of the solution increases from 0°C to 60°C,the overpotential of the material drops from 115m V to 75m V at 10 m A cm^-2.In the second part,the overpotential of the material will also change significantly with different p H of the test solution.As the p H of the solution decreases,the overpotential of the catalyst decreases significantly.The overpotential at p H=14 is132 m V,which is in strong contrast with the overpotential at p H=12.1,which is much greater than1000 m V.Through the stability test,it can be found that the material has good stability.Secondly,it is expected that carbon doping can improve the conductivity of the material to improve the catalytic performance.On the basis of preparing Co:Fe S₂/Co S₂,the material was doped with carbon.Because the addition of carbon can not only improve the conductivity of the material itself and between the material and the substrate,but also can form carbon defects to provide more active sites to optimize catalytic performance.At room temperature,the overpotential of the material in a 0.5 M H₂SO₄ solution is 88m V(current density is 10 m A cm^-2).Compared with the performance of the material without carbon doping,it is obviously optimized.Finally,the catalytic performance of other transition metal compounds was studied,and the micro/nano structure of Ni S₂ catalyst was controlled by changing the experimental scheme.Using sulfur powder and sodium 3-mercapto-1-propanesulfonate（MPS）as the source of the sulfur,we prepare a high-performance Ni S₂ catalyst with a polyhedral structure.The overpotential of Ni S₂ of the disulfide source is 131m V in 0.5 M H₂SO₄ at room temperature,which is significantly higher than that of single sulfur source（197 m V）and MPS（261 m V）respectively.