Study On Surface Modification Of Stainless Steel Based Electrode And Its Electrochemical Performance

In recent years,with the the increasing environmental pollution and the deepening of people's understanding of non-renewable resources,there is an urgent need to find a cleaner and more efficient energy supply method to reduce dependence on fossil energy.Hydrogen is considered to be the most promising energy carrier and the best substitute for fossil energy in the future due to its clean and efficient properties.There are many ways to produce hydrogen,and electrolyzing water is one of the more effective methods.However,the energy consumption of direct electrolysis water is high,so a suitable catalyst is needed to reduce the energy barrier of water decomposition reaction.Nickel iron hydroxide composite materials have attracted wide attention of researchers due to their good catalytic performance,low cost and abundant resources.The main components of stainless steel are catalytically active metals(Ni,Fe,and Cr),and stainless steel is non-toxic and low cost.Therefore,applying them in the electrolytic water process can greatly reduce the process cost.In sight of that,316L stainless steel fiber felt was selected as the target,and the electrode based stainless steel was modified by a series of methods to improve its electrolytic catalytic water decomposition performance.The research contents and results are as follows:(1)Compared with the traditional method,in-situ modification of the stainless steel electrode by cyclic voltammetry(CV)is simple and easy,and can be directly modified in alkaline electrolyte.So that the extra source of nickel and iron need not be injected.The paper explores the effects of CV scanning range,scanning rate,the number of cycles and electrolyte concentration on the catalytic performance of stainless steel for oxygen evolution,in order to determine the optimal parameters.In addition,the morphology and element composition of SSF-F were further investigated.Finally,SSF-F was utilized in the electrolytic carbonate.The results of the section indicate that the overpotential of SSF-F is only 230 mV at 10 mA cm-2 in 1 mol L-1 KOH,and the Tafel slope of is only 69 mV dec-1 in 0.5 mol L-1 Na2CO3/NaHCO3,exhibiting good electrocatalytic performance for oxygen evolution reaction in both alkaline and carbonate solutions.(2)In order to improve the hydrogen evolution catalytic performance of the stainless steel electrode,sulfur and phosphorus elements were doped in it.The experimental results show that the sulfur element doping can better improve the hydrogen evolution catalytic activity of the stainless steel electrode than the phosphorus element.Through the further studying of the influence of calcination temperature,calcination time and doping amount of sulfur on the hydrogen evolution performance of the sulfide modified stainless steel electrode,the optimal sulfidation modification process parameters were determined.It can be indicated from electrochemical test that the best SSF@S electrode exhibits good hydrogen evolution catalytic activity and stability,the hydrogen evolution overpotential is 150 mV in 1 mol L-1 KOH at 10 mA cm-2,and and the change in potential for 12 h is only about 3 mV.(3)The SSF@NiFe electrode with dual-functional catalytic properties was obtained by constant current deposition nickel-iron hydroxide nanosheet onto stainless steel electrode.The optimal preparation process parameters of the constant current were determined by studying the effects of the proportion of metal elements in the electrolyte,the total metal ion concentration,the deposition current density and the deposition time on the hydrogen evolution and oxygen evolution performance of the electrode.The results show that the optimal molar ratio of nickel to iron is 2:1,the total metal ion concentration in the electrolyte precursor salt is 96 mmol L-1,the electrodeposition current density is 50 mA cm-2,and the electrodeposition time is 120 s.Based on this,this electrode was used as the cathode and anode for the performance test of full water decomposition,the results show that the electrode has a lower potentials of 1.55 V and 1.80 V at 10 mA cm-2 and 100 mA cm-2,respectively.In addition,the electrode can work stably more than 10 h in 1 M KOH.