Preparation Of Iron-nickel Alloy Self-supported Electrocatalyst By Corrosion Method

As a promising secondary energy source,hydrogen energy can be obtained through water electrolysis technology.The water electrolysis reaction consists of the cathode hydrogen evolution reaction（HER）and the anode oxygen evolution reaction（OER）.Compared with HER,OER has a more complicated process and higher energy consumption,which has attracted more attention from researchers.Among OER catalysts,noble metal compounds such as Ir O₂ and Ru O₂ have high catalytic activity,but their reserves are limited and the price is high.Therefore,related researches on non-precious metal catalysts such as nickel and iron have become current research hotspots and difficulties.However,the current preparation methods of non-precious metal electrocatalysts often have many steps and harsh conditions,making it difficult to achieve low-cost macro-production.On the other hand,metal corrosion is a common natural phenomenon.The corrosion products of many metals such as nickel and iron in sulfur-or oxygen-containing environments are often sulfides or（hydrogen）oxides,and these products usually have OER or HER catalytic activity.Based on this idea,this thesis uses foamed iron-nickel alloy（NIF）as the base,and uses various corrosion methods such as Na₂S solution hydrothermal,chloride solution water bath,and Na₂S₂O₃solution immersion to successfully prepare a self-supporting electrocatalyst.The test results show that The prepared catalyst has excellent OER catalytic performance.The main work is as follows:（1）Na₂S solution high temperature and high pressure corrosion NIF.Under hydrothermal,high temperature and high-pressure conditions,the main components of Fe S and Ni₃S₂ grown on the surface of NIF in situ are Fe S and Ni₃S₂,which are nano-sheet structures and can be used as OER catalysts.The catalyst has excellent OER activity:η₁₀=184 m V,η₁₀₀=227 m V in 1 M KOH solution;η₁₀=198 m V,η₁₀₀=332m V in 1 M KOH+0.5 M NaCl solution.The noble metal Pt/C/NIF is used as the cathode,and the prepared electrode material is used as the anode to form an electrolytic cell.The decomposition voltage is 1.57 V when the current density is 10 m A cm^-2.In addition,the material has good stability:the stability test is performed at a current density of50m A cm^-2 for 25 h,and the voltage is basically unchanged.Based on various characterization results such as electric double layer capacitance measurement,contact angle measurement,impedance spectroscopy measurement,etc.,it is speculated that the excellent OER performance of the catalyst is mainly due to:the nanosheet structure exposes more active sites;the hydrophilicity and aerophobicity are both beneficial Full contact with the electrolyte,but also the rapid release of bubbles;a small charge transfer resistance（Rct）improves the charge transfer capacity,and the self-sufficient in-situ growth method avoids the use of binders,thereby reducing contact resistance and enhancing OER activity.（2）Temperature and atmospheric pressure corrosion NIF in NaCl-MgCl₂ solution.Under such medium temperature and normal pressure conditions,the self-supporting nano flake iron-nickel metal hydroxide NiFe（OH）_x is prepared on the surface of the NIF with the help of the corrosion effect of chloride ions.This substance shows excellent OER activity and stability:η₁₀=170 m V,η₁₀₀=301 m V;in 1 M KOH+0.5 M NaCl solution,η₁₀₀=369 m V.The electrolytic cell composed of the noble metal Pt/C/NIF as the cathode and the prepared electrode material as the anode has a decomposition voltage of 1.52 V at a current density of 10 m A cm^-2.Based on various characterization results,its excellent OER performance can still be attributed to factors such as large specific surface area,many exposed active sites,good hydrophilic and air-repellent properties,high intrinsic activity,and low contact resistance.（3）Na₂S₂O₃ solution at room temperature and pressure corrosion NIF.This preparation method is very gentle（room temperature and normal pressure）and fast（just soaking for a few minutes）,and the sulfur-doped iron-nickel metal hydroxide nanosheet catalyst S-（Ni,Fe）OOH can be prepared.This catalyst has excellent OER performance and stability in alkaline electrolyte and simulated seawater electrolyte:in 1 M KOH,η₁₀=176 m V,η₁₀₀=279 m V;in 1 M KOH+0.5 M NaCl solution,η₁₀=234 m V,η₁₀₀=336m V.It has excellent stability for 50 h when the current density is 200 m A cm^-2.The electrolytic cell composed of the noble metal Pt/C/NIF as the cathode and the prepared electrode material as the anode has a decomposition voltage of 1.54 V at a current density of 10 m A cm^-2 and has good hydrolysis stability.Based on various characterization results,it is inferred that the excellent OER performance of S-（Ni,Fe）OOH is mainly due to the large specific surface area,many active sites exposed,good hydrophilicity and air repellency,high intrinsic activity,low contact resistance,etc.