Preparation Of Au-based Catalyst And Its Application In Borohydride Electrocatalytic Oxidation Reaction

Direct sodium borohydride fuel cell（DBFC）uses sodium borohydride alkali solution as fuel,which has attracted the interest of many researchers because of their high theoretical specific energy and high theoretical voltage.Among them,noble metals are often needed as catalysts during the oxidation reaction of BH₄^-,so reducing the cost of the catalyst and improving the catalytic activity of the catalyst are the key.The precious metal Au has a high coulombic efficiency during the reaction process,and the electron transfer number is close to 8,but its reaction kinetics is slow,so it is necessary to modify the anode catalyst.In this paper,three different series of anode catalysts were prepared by using nitrogen-doped carbon to coat transition metals and alloys to modify the precious metal Au.Use physical means to characterize the structure and morphology of the catalyst material;use electrochemical testing methods to study the electrocatalytic oxidation activity of BH₄^-.The main findings are as follows:1.A two-step method was used to prepare Au/Co@CN/C catalysts with different mass ratios.The diameter of Co@CN is about 70～80 nm,and Au nanoparticles are supported on the surface of Co@CN nanospheres.The research results show that the doping of Co@CN significantly enhances the electrocatalytic oxidation activity of Au catalyst for BH₄^-.Among them,Au_（50）/Co@CN_（50）/C showed the best electrocatalytic activity,and the peak current density for BH₄^-electrooxidation reached 43.9 m A cm^-2,which was 19.1 m A cm^-2 higher than that of a single precious metal Au catalyst.2.A two-step method was used to prepare Au/Co₂P@CN/C catalysts with different mass ratios.Au/Co₂P@CN/C is loaded on the surface of carbon black in a regular spherical shape.The particle size of metal nanoparticles is mainly distributed between 10 nm and 40 nm,and the average particle size is about 23.4 nm.The research results show that:Co₂P@CN has a significant effect on improving the catalytic performance of the catalyst.Among them,the peak current density of Au_（50）/Co₂P@CN_（50）/C for BH₄^-electrooxidation reached 48.4 m A cm^-2,and the electrochemical active area was increased by 208.1 cm² mg^-1 compared with a single precious metal catalyst.3.A two-step method was used to prepare Au/MnCoP@CN/C catalysts with different mass ratios.Au/MnCoP@CN/C nanospheres are supported on the surface of carbon black with good dispersion.The particle size is mainly distributed between 9nm and 30 nm,and the average particle size of metal nanoparticles is 17 nm.Electrochemical research results show that Au/MnCoP@CN/C has better electrocatalytic oxidation activity for BH₄^-,although the peak current density of the electrocatalytic oxidation of BH₄^-is not greatly improved compared with the Au/Co₂P@CN/C catalyst,the further doping of Mn makes the number of transferred electrons reach 6.9,which is close to the theoretical electron transfer number of Au.