Preparation Of Carbon Material Supported Cobalt-based Alloy Electrocatalysts And Study Of Their Performance In Oxygen Reduction/hydrogen Evolution Reaction

With the rapid development of science and technology,the world is facing problems such as energy consumption and environmental pollution.Electrocatalytic energy technology plays a crucial role in achieving a carbon-neutral future.A fossil fuel-free energy infrastructure is a blueprint for the future,which could be a hydrogen-based energy system,including solar-powered hydrogen production by water electrolysis,hydrogen fuel cells,etc.Among them,hydrogen production from electrolytic water is popular among researchers because of its high purity and low cost,and it is an important area for energy development nowadays.In addition,fuel cells combine oxygen and hydrogen to convert chemical energy into electrical energy,making them a promising source of power.However,at this stage of research on both,precious metal-based catalysts are usually used,and their limited reserves,high prices and lack of durability limit the large-scale application of these new energy systems.Therefore,the design of catalysts with low cost,high catalytic activity and stability is the main task of current research.This thesis focuses on catalysts for hydrogen precipitation reactions（HER）and oxygen reduction reactions（ORR）.We have designed and synthesized two electrocatalysts,which are cobalt（Co）-based alloy catalysts loaded with carbon materials,using an interfacial modulation approach.The main research contents are as follows:（1）First,Co Zn hydroxide precursors were prepared using a simple hydrothermal synthesis method.Next,melamine was utilized as the carbon source.The catalyst material in the form of carbon nanofibers was prepared by high-temperature pyrolysis,and Co Zn alloy nanoparticles were encapsulated in carbon nanofibers（Co Zn/N-CNFs）.The ratio of Co Zn hydroxide precursor to melamine was optimized,where the optimal ratio was 1:5.The half-wave potential of the modified sample in alkaline（0.1 M KOH）electrolyte could reach 0.814 V,which is close to the half-wave potential of commercial Pt/C catalysts.In addition,the assembled zinc air batteries（ZABs）with good specific capacity(756.7 m Ah g^-1),high power density(223.8 m W cm^-2)and long service life（87.5 h）using the material as a cathode catalyst have shown good promise for ZABs applications.（2）The carbon nanotubes were doped/removed with N and the formed defective carbon nanotubes were used as carbon carriers.Then the mixture of aqueous solution with H₂Pt Cl₆and Co（NO₃）₂was well stirred.Finally,the defective carbon nanotubes loaded Co/Pt alloy composites（Pt/Co（3/2）@D-CNT）were obtained using UV photochemical reduction method.The experimental results show that the elemental content of Pt in the prepared composites is only 1.74 wt%.It has very excellent ORR performance under alkaline conditions,and the onset potential（0.99 V）and half-wave potential（0.84 V）are significantly better than those of commercial Pt/C catalysts.In addition,the material exhibits excellent HER performance under alkaline conditions,requiring an overpotential of only 97.47 m V at current densities up to 300 m A cm^-2and retaining 89.2%activity after 24 h stability testing.The materials also showed excellent catalytic activity(300 m A cm^-2,47.22 m V)and excellent stability（24 h,95.3%）under acidic conditions.Finally,given the excellent HER performance of Pt/Co（3/2）@D-CNT,it has excellent water resolution performance(10 m A cm^-2,1.507 m V)and good stability（56 h,80%）as a total water resolution cathode catalyst.