Preparation Of Polysulfur （Selenium） Supported By Transition Metal Doped Carbon Materials And Study On The Performance Of Electrocatalytic Water Splitting

The burning of traditional fossil fuels has brought serious environmental problems to the world,so there is an urgent need to seek new energy sources to replace traditional fossil fuels to solve this problem.As a clean,efficient and sustainable new energy,hydrogen energy is an ideal substitute for traditional fossil fuels.Nowadays,hydrogen production from water electrolysis is a green and sustainable energy conversion technology,but it is still difficult to achieve industrial application.Noble metal-based catalysts（Pt/Ir O₂/Ru O₂,etc.）are the most efficient catalysts,but it is necessary to seek inexpensive and earth-abundant catalysts to solve this difficulty due to their high price and low earth reserves.Currently,transition metal catalyst materials have received extensive attention from researchers because of their excellent catalytic activity in hydrogen evolution reaction（HER）and oxygen evolution reaction（OER）.In this paper,on one hand,non-metal（N/S）doping is used,and on the other hand,transition metal composites are formed by doping trace noble metals to realize the control of the morphology,structure,active sites and even intrinsic activity of the material,thereby improving the HER and OER activity of catalysts at neutral and full range of p H.The specific research works are as follows:1.For the first time,S with active bridging S_n^2-is supported on a Co Fe alloy embedded in N-doped carbon nanosheets（S-Co Fe@NC）by a templating method,which exhibits extremely strong HER activity in neutral media.This sample exhibits the same HER performance as commercial Pt/C under neutral conditions,requiring only an overpotential of 37 m V to reach a current density of 10 m A cm^-2,and the Tafel slope of only 34 m V dec^-1.Systematic studies show that the strong interaction between bridging S_n^2-and Co Fe@NC introduces M-S_n^2-as a powerful catalytic site for HER,and this also facilitates charge exchange.Meanwhile,the special interconnected network structure of the synthesized nanosheets provides structural advantages for obtaining active sites and electrocatalytic charge transfer.Therefore,this study paves the way for the development of novel sulfur-based electrocatalysts for neutral water splitting with efficient HER performance.2.In this chapter,an efficient single-atom doping strategy is established to enhance the water-splitting performance of MOFs.A simple solvothermal strategy is utilized to construct excellent metal-organic frameworks（MOFs）electrocatalysts（Co Ir-BDC@NF-x）by introducing microdispersed noble metal Ir.Ir doping can not only serve as a catalytic site,but also tune the electronic structure of Co to facilitate OER and HER processes.Notably,the synthesized Co Ir-BDC@NF-4 exhibits good OER activity in alkaline solution.At a current density of 50 m A cm^-2,the overpotential is only 274 m V.At the same time,it displays good HER activity in wide p H range.At a current density of 50 m A cm^-2,the overpotentials are 70,44,and 74 m V in 0.5 M H₂SO₄,1.0 M KOH,and 1.0 M PBS solutions,respectively.More interestingly,when Co Ir-BDC@NF-4 is used as the electrode of the two-electrode system,it exhibits a good overall water splitting performance,which only requires 1.494 V to achieve a current density of 10 m A cm^-2.3.A Ru-loaded Co Se₂material（Ru-Co Se₂@NF）on nickel foam is designed for the first time by a simple two-step solvothermal method,which exhibits excellent HER and OER activities under neutral conditions.The oxygen evolution reaction of Ru-Co Se₂@NCF only requires an overpotential of 110 m V to reach a current density of 50 m A cm^-2,and its hydrogen evolution reaction reaches a current density of 50 m A cm^-2at an overpotential of 65 m V.The systematic study of the comparative samples shows that the loading of a small amount of Ru not only improves the charge transport rate of the precursor but also increases the active specific surface area,thereby increasing the number of active sites.At the same time,its small Tafel slope suggests that Ru loading improves the electrochemical kinetics.In addition,the structure formed by the three-dimensional flower-based N-doped C material not only provides more active sites but also accelerates charge transfer.This study will provide different insights into the design of novel sulfur-based materials as efficient bifunctional electrocatalysts under neutral conditions.