Preparation And Electrochemical Performance Of Hollow Pt-based Nanocatalysts

In recent years,platinum-based catalysts have proven to be the most effective and promising materials for the renewable energy conversion technologies due to their special physicochemical properties.However,Pt resources on the planet are scarce and costly,which greatly limits their commercial applications.Therefore,to solve the cost and activity problems faced by platinum-based catalysts,it is very urgent to maximize the Pt utilization rate and enhance its electrocatalytic performance.The research work of this thesis provides new research ideas for the design and preparation of hollow platinum-based nanocatalysts for efficient energy conversion in the hydrogen evolution reaction?HER?and oxygen reduction reaction?ORR?.The main research results obtained are as follows:Nickel nanowires with the diameter of 90-150 nm were prepared by using ethylene glycol assisted reduction method as a sacrificial template,and a series of carbon black-supported hollow PtNi nanostring catalysts were synthesized by displacement reaction and acid etching.And the effects of preparation conditions on catalyst structure and the HER performance were studied.The results show that the carbon black-supported hollow PtNi nanostring catalyst obtained after etching for 60 min with 200?L hydrochloric acid at the reaction time of 20 min and the reaction temperature of 90°C has the best HER performance.In a 1.0 mol/L KOH electrolyte,the catalyst has an overpotential of 44 mV at the current density of 10 mA/cm².After a cycle stability test of 50000 cycles,the half-wave potemtial dropped by only 0.056 V,confirming that the hollow PtNi nanosring catalyst maintains excellent HER stability.In oreder to further explore the influence of nickel nanowire template on the structure and electrochemical properties of the final product,the smaller nickel nanowires with the diameter of 25-75 nm were prepared by using the simpler ethylene glycol reduction method as a template,and a series of carbon black-supported hollow PtNi nanochain catalysts were synthesized by displacement reaction and acid etching.And the effects of preparation conditions on the structure of the catalyst and the ORR performance were investigated.The hollow structure facilitates electron transfer in the electrocatalytic process,and the rich structural defects facilitate the adsorption of oxygen molecules on the catalyst surface and the breaking of chemical bonds.The results show that the carbon black-supported hollow PtNi nanochain catalyst obtained by etching with 250?L hydrochloric acid for 210 min at the reaction time of40 min at 30?,which has the best ORR performance.The hollow structure facilitates the electron transfer in the electrocatalytic process,and the rich structural defects facilitate the adsorption of oxygen molecules on the catalyst surface and the breaking of chemical bonds.The test results show that the half-wave potential of the catalyst can be as high as 0.965 V in the0.1 mol/L HClO₄ acidic electrolyte,and in the 0.90 V reversible hydrogen electrode,its mass activities and specific activities were 4.6 A/mg and 11.45 mA/cm²,respectively,18 times and29 times that of commercial Pt/C catalysts.In addition,after 50000 cycles of testing,its activity remained essentially unchanged,investigate that the hollow nanochain catalyst has excellent ORR stability.Based on the above-mentioned step-by-step synthesis of hollow PtNi nanostrings and nanochains catalysts,the hollow PtNiCo and PtNiCoFe nanochain catalysts supported by carbon black were synthesized by one-pot method,and the effects of preparation conditions on the structure,the HER and ORR performance of the catalysts were studied.The test results show that the carbon black-supported hollow PtNiCo catalyst shows the best HER catalytic performance.At a current density of 50 mA/cm²,the overpotential is only 52.6 mV.Meanwhile,the ORR result shows that the half-wave potential is 0.881 V.It indicates that it alos has excellent ORR catalytic activity.