| Hydrogen is considered to be the most ideal energy carrier in the future.Due to its high energy density,clean combustion products and sustainable recycling,the preparation and development of hydrogen has always been a research hotspot in the energy field.Among the many hydrogen production technologies,Proton exchange membrane（PEM）electrolysis of water hydrogen production technology has a series of advantages such as simple ingredients,high hydrogen production concentration and simple operation.Compared with fossil reforming hydrogen production with low production concentration and serious carbon emissions,it greatly meets people’s expectations for hydrogen production process.However,the complex mechanism of anodic side oxygen evolution（OER）in PEM electrolytic cell and the high price of common noble metal materials are an important link to limit the development of the technology.In this paper,the OER performance of iridium oxide（Ir O2）supported several carbides（WC,Ta C and Si C）catalysts under acidic conditions was studied in order to reduce the catalyst cost and improve the battery life.At the same time,the effects of different holding time and noble metal content on the reactivity and life of Ir O2-WC,and the relationship between the microstructure and electrochemical performance of Ru O2@Ir O2catalyst were further discussed.Firstly,the optimum temperature for preparing WC,Ta C and Si C carriers by carbothermic reduction was investigated.According to XRD analysis,WC,Ta C prepared at 1400℃and commercial Si C were used as catalyst carriers in this chapter.Subsequently,Ir O2-WC,Ir O2-Ta C and Ir O2-Si C anodic catalysts were prepared using Ir Cl3as raw material and Ir O2was attached to the surface of the carrier by Adams melting method.The results show that the oxygen evolution activity of the carbide carrier itself is low,and the oxygen evolution activity of the material almost comes from the surface loaded Ir O2.In the calcination process of Ir O2,WC and Si C carriers are stable and have no obvious phase transformation except for the formation of a small amount of oxygen-containing chemical bonds on the surface.Ta C generates a large amount of Na Ta O3in the loading process,which affects the active area and catalytic performance.The crystallization of Ir O2on WC surface is slow,and Ir O2is mainly wrapped around WC in fibrous form.When the oxygen evolution reaction is at a high current density（above 30 m A/cm~2）,the activity of Ir O2is higher than that of Ir O2-Ta C and Ir O2-Si C.Ir O2-Si C has the strongest catalytic durability,and the potential attenuates only 55 m V after 20 h continuous testing.Secondly,considering the unique Ir O2structure on the Ir O2-WC’s surface in the previous experiment,the purpose of this chapter is to improved the oxygen evolution performance of Ir O2-WC by regulating the holding time（4,5,6 h）and the content of Ir O2（20,40,60 wt%）.In each sample,WC carrier phase was stable and morphology did not change significantly.The holding time mainly affects the transformation process of Ir O2from fibrous to spherical particles.The spherical Ir O2formed at 5 and 6 h of holding time has a stable structure,and the long time of insulation promotes the refinement of surface particles..The high content of Ir O2load can provide more active sites for the material and enhance the oxygen evolution efficiency of the material by increasing the reaction area.After comprehensive consideration of oxygen evolution performance,stability and material cost,it is considered that the Ir O2-WC catalyst prepared at 40 wt%Ir O2content under 5 h thermal insulation has the best application prospect.The overpotential of the sample was 259 m V at the current density of 10 m A/cm~2,and the potential deviation was35 m V after continuous testing for 24 h.The single cell current of the PEM electrode（Cathode catalyst 40 wt%Pt/C）can reach 0.77A@2.2 V at 80℃.Finally,Ru O2@Ir O2anode catalyst with Ru O2as core was prepared by hydrothermal method and Adams melting method.The average grain size of Ru O2prepared by hydrothermal method is less than 10 nm,it has excellent oxygen evolution performance with an overpotential of 201 m V at 10 m A/cm~2current density.Appropriate amount of external Ir O2has a good protective effect on Ru O2,which makes Ru O2@Ir O2catalyst exhibit better performance than Ru O2particles at high current density.The overpotential of Ru O2@Ir O2-1 catalyst prepared with Ru O2:Ir O2=8:2 at 100 m A/cm~2current density is 364 m V,the potential shift is only 29 m V after 20 h.The outer layer of Ir O2effectively alleviates the transition oxidation dissolution of lattice oxygen in Ru O2and improves the durability of the material. |
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