Preparation Of Carbon-based Iridium Oxide Composites And Their Electrocatalytic Performance

Increasing energy demand and environmental pollution have stimulated research on renewable energy conversion and storage.The development of efficient and stable catalysts for oxygen evolution reaction(OER)is the core of renewable energy technology.Although non-noble metal catalysts have been reported as oxygen evolution catalysts in electrolytic water,most non-noble metal catalysts can only be used in alkaline electrolyte solutions and lack extensive adaptability.At present,the high corrosive environment of electrochemical water decomposition still needs to use noble metal-based electrocatalysts,and the noble metal-based catalyst iridium oxide(IrO2)is a research hot spot.The problem of IrO2 as an oxygen evolution catalyst is easy agglomeration and low conductivity.Therefore,how to improve the dispersion and conductivity of IrO2 has become the focus of research.This paper uses multi-walled carbon nanotubes and graphene oxide with high specific surface area as the carrier,intends to increase the dispersibility of IrO2 nanoparticles,improve the atom utilization and expose more active sites,so that the composite catalyst has more catalytic active center.The following contents were specifically carried out:(1)IrO2 nanoparticles were successfully loaded onto functionalized multiwalled carbon nanotubes by hydrothermal method,while samples calcined at different temperatures were compared(350,400,450 and 500℃).The structure of composites was studied by TEM,XRD,Raman,XPS and other characterization methods,and the effects of IrO2@MWCNT composites on the physical and chemical properties and electrochemical properties of OER at different temperatures were evaluated by CV,LSV,EIS and other methods.The results showed that as the calcination temperature increased,MWCNTs gradually disappeared,but the tubular structure formed by IrO2 nanoparticles remained,the size and crystallinity of IrO2 nanoparticles also increased.Electrochemical studies have shown that IrO2@MWCNT-400℃only needs an OER overpotential of 40 mV(vs.SCE)to reach a current density of 10 mA cm-2 and has excellent oxygen evolution activity.Its high electrocatalytic activity can be attributed to the high dispersion of IrO2 on the surface of MWCNTs to prevent agglomeration,resulting in a higher specific surface area of the catalytic center,at the same time,MWCNTs enhanced the electron transfer rate and improved the electrocatalytic activity.(2)IrO2@GO composites at different temperatures were prepared by hydrothermal and calcination methods.The material is a composite structure of IrO2 nanoparticles uniformly distributed on a graphene oxide carrier with a high specific surface area.By studying the electrochemical performance of IrO2@GO composites in OER at different temperatures,it is found that IrO2@GO-350℃ exhibits excellent oxygen evolution reaction activity,and its OER overpotential is 50 mV(vs.SCE)at a current density of 10 mA cm-2.This is due to the GO nanosheets can be used as a support to uniformly load IrO2 nanoparticles,which enhances the utilization of IrO2 active materials and exposes more active sites.Therefore,the electrocatalytic activity is significantly improved.(3)Using element doping strategy,Pt/IrO2@MWCNT-400℃ composite catalyst and Pt/IrO2@GO-350℃composite catalyst were successfully prepared by chemical reduction method.From the results of the morphology study,it can be seen that Pt nanoparticles are uniformly dispersed on the surface of IrO2@MWCNT-400℃ and IrO2@GO-350℃,respectively.The electrochemical test showed that Pt/IrO2@MWCNT-400℃ and Pt/IrO2@GO-350℃ showed significantly enhanced oxygen evolution reaction activity compared with the composite without Pt doping,respectively.At a current density of 10 mA cm-2,the OER overpotential value of Pt/IrO2@MWCNT-400℃ is 28 mV(vs.SCE),the Tafel slope value is 83.2 mV dec-1,and the overpotential value of Pt/IrO2@GO-350℃ is 42 mV(vs.SCE),the Tafel slope value is 84.9 mV dec-1.The research results show that the high catalytic activity displayed by Pt/IrO2@MWCNT-400℃ and Pt/IrO2@GO-350℃ is mainly due to the fact that carbon nanotubes and graphene oxide nanosheets can uniformly load Pt/IrO2 nanoparticles,exposed more reactive sites.In addition,the excellent conductivity of carbon nanotubes and graphene oxide nanosheets enhances the electron transfer rate of the catalyst,where Pt optimizes the IrO2 nanostructure and their dispersibility to improve the electrocatalytic activity.The research in this paper will provide certain theoretical data for the efficient use of IrO2 in the field of electrolytic water.