Study On Preparation And Performance Of Metal Oxide Supported Electrocatalytic Hydrogen Evolution Catalyst

Although the use of fossil fuels such as coal,oil and natural gas has promoted the rapid development of society,it has also caused environmental pollution.Fossil fuels are non-renewable energy sources,and the continuous consumption of fossil fuels will eventually lead to energy depletion.Looking for renewable and clean energy to replace fossil fuels can well solve the above problems.Hydrogen is very popular among researchers due to its environmental friendliness and a wide range of sources.The development of hydrogen production technology by water splitting provides technical support for the production of hydrogen.At present,water splitting is recognized as a feasible solution to the energy crisis due to their low pollution emissions and mild operating conditions.However,the slow reaction kinetics,low catalytic efficiency and poor catalyst stability of water splitting technology limit its commercial applications.This requires the research of catalysts with high catalytic efficiency,good stability and low price.It is found that nanomaterials have shown great potential in the field of electrocatalysis.In this work,metal oxides supported noble metals are used as catalysts,and the catalytic activity of the catalysts for hydrogen evolution reaction（HER）is studied in alkaline environments.The work is divided into the following three parts.1.Zinc oxide（ZnO）and molybdenum disulfide（Mo S₂）are favored by researchers due to their excellent physical and chemical properties.In this part,Mo S₂,ZnO and Mo S₂-ZnO composites with heterogeneous structure are successfully synthesized by hydrothermal method.The physical properties of the samples are characterized by XRD,FESEM,TEM and XPS;and the catalytic activity of the samples for hydrogen evolution reaction is tested in 0.1 M KOH solution.XRD results show the samples with high purity are successfully synthesized;FESEM and TEM results showed that ZnO is successfully grown on Mo S₂nanosheets.The electrochemical results show that the heterostructure between ZnO and Mo S₂is beneficial to the catalytic activity of the samples for hydrogen evolution reaction.The catalytic activity of Mo S₂-ZnO increases with the increase of the amount of Mo S₂.40%Mo S₂-ZnO has the best catalytic activity,and its overpotential is 492 m V.This is due to the increase of the electron transfer rate and the number of active sites of the catalyst after the recombination of ZnO and Mo S₂.2.In this part,Ag-ZnO,Mo S₂-ZnO and Ag-Mo S₂-ZnO are successfully synthesized by hydrothermal method.The physical properties of the samples are characterized by FESEM,XRD,TEM,EDS and BET.The catalytic activity of the samples for hydrogen evolution reaction is investigated by an electrochemical workstation in 0.1 M KOH.XRD results indicate the catalysts have good crystallinity and purity.According to the FESEM results,Ag and ZnO are evenly distributed on the Mo S₂nanosheets in the 5%Ag-5%Mo S₂-ZnO.LSV results show that adding Ag or Mo S₂to ZnO can improve its catalytic activity,5%Mo S₂-ZnO has better catalytic activity than 5%Ag-ZnO.The catalytic activity of adding Ag and Mo S₂to ZnO to form a three-way catalyst is significantly higher than that of adding Ag or Mo S₂to ZnO to form a two-way catalyst.5%Ag-5%Mo S₂-ZnO has the best catalytic activity,and its overpotential is 568 m V,which is mainly due to the synergistic effect of heterojunction and Ag.3.In this part,Pd/TiO₂composites are successfully prepared by anodic oxidation and electrodeposition.When the time of depositing Pd is 15 min and 5 min,the electrocatalyst is marked as 15 min Pd/TiO₂and 5 min Pd/TiO₂respectively.The physical properties of Pd/TiO₂composites are characterized by XRD,EDS,FESEM and XPS.The catalytic activity of Pd/TiO₂for hydrogen evolution reaction in 1M KOH solution and 1M Na₂SO₄solution is characterized by the electrochemical workstation.XRD results showed that Pd/TiO₂is successfully synthesized;the EDS and XPS results confirmed the above results.FESEM results show that Pd nanoparticles are uniformly distributed on the surface of TiO₂nanotube arrays.The electrochemical results show that Pd/TiO₂has better catalytic activity than TiO₂.In 1M KOH solution,the overpotential of 15 min Pd/TiO₂is positively shifted by 98 m V and 588 m V compared with the overpotential of 5 min Pd/TiO₂and TiO₂-2h;the 15 min Pd/TiO₂still has good catalytic activity after 2000 CV cycles.The catalytic performance of all catalysts in 1M KOH is better than that in 1M Na₂SO₄.The experimental results show that the use of metal oxides supported noble metals to prepare catalysts is a feasible solution.On the one hand,the metal oxide can increase the dispersibility of the noble metal particles;on the other hand,the noble metal particles can increase the conductivity and the number of active sites of the catalyst,thereby improving the catalytic performance of the catalyst for HER.