Design Of Metal-based Catalysts And Study On Electrocatalytic Oxygen Reduction And Hydrazine Hydrate-assisted Hydrogen Production

In the 21st century,with the rapid development of industry,energy issues have attracted more and more attention from the public.Based on this,the development of a new energy system with high efficiency,energy saving,clean and pollution-free is urgent.The metal-air battery is a green and environmentally friendly electrochemical energy conversion system.It directly converts chemical energy into electrical energy through oxygen reduction reaction（ORR）.It has the advantages of high conversion efficiency,high energy density,and zero pollution.It is considered the best One of the potential new energy systems.However,ORR at the cathode of the battery is a slow kinetics process.At present,the catalyst of ORR is mainly a Pt-based catalyst.Due to its high cost and poor stability,the development of zinc-air batteries is limited.Therefore,it is very important to find a cheap,stable and efficient ORR catalyst.At the same time,the massive burning of fossil fuels has not only caused huge pollution to the environment,but also faced the crisis of energy shortages.Finding new alternative energy sources has become a top priority.As a green renewable energy source,hydrogen energy generated from water electrolysis is expected to solve the energy crisis facing mankind.Therefore,the development of high-efficiency hydrogen production catalysts is also a research hotspot in academia.This thesis mainly focuses on the above two issues to carry out the following work.（1）Most of the ORR catalysts that have been reported are only active under alkaline conditions.There is an urgent need to extend the catalytic activity of ORR catalysts to a wider p H range.Based on this,this paper prepared an atom-dispersed Fe-Zn pair（Fe-Zn-SA/NC）fixed on the porous N-doped C framework,which can effectively function as an ORR catalyst in the entire p H range.In 0.1 M HCl O₄,0.1 M KOH and 0.1 M PBS electrolytes,it can achieve high half-wave potentials of 0.78,0.85and 0.72 V respectively,which is comparable to Pt/C.When assembled into a Zn-air battery,its power density and stability can reach 167.2 m W·cm^-2 and 120 h,respectively.Theoretical calculations show that the excellent catalytic activity of Fe-Zn-SA/NC comes from Fe-Zn-N₆,which can help reduce the energy barrier of ORR.This work proves that the Fe-Zn pair is expected to be a substitute for Pt catalysts and provides new insights for the application of diatomic catalysts to ORR in a wider p H range.（2）Using the hydrazine oxidation reaction（HzOR）to replace the anode water oxidation reaction is an effective way to reduce the overpotential of hydrogen produced by water electrolysis.In this paper,we have prepared a highly efficient dual-function electrocatalyst with Rh nanoparticles（Rh-NS-HCS）on hollow C doped with N and S,which can achieve hydrazine-assisted hydrogen production（OHz S）under alkaline conditions.Specifically,Rh-NS-HCS shows a low hydrogen evolution reaction（HER）overpotential in alkaline electrolytes,reaching a current density of 10 m A·cm^-2 at only70 m V.At the same time,Rh-NS-HCS also shows excellent Hz OR performance in alkaline electrolyte.Therefore,Rh-NS-HCS is used as a dual-function electrocatalyst for HER and Hz OR,and a simple electrolytic cell assembled into a two-electrode system also shows better performance than Pt/C catalyst.Compared with the corresponding fully decomposed water system,energy consumption can be saved.This work developed an efficient dual-function electrocatalyst for hydrazine-assisted hydrogen production,and provided certain insights for reducing the cost of large-scale industrial hydrogen production.