Preparation Of Au-based Nanocatalyst And Its Application In Bh₄^-Electrocatalytic Oxidation

Direct sodium borohydride fuel cell（DBFC）has been paid much attention by researchers since its introduction.Sodium borohydride（NaBH₄）is used in DBFC as a carbon-free energy carrier with high energy density.However,the competitive hydrolysis of BH₄^-co-existing in the electrooxidation process of BH₄^-and the high price of the precious metal necessary for the catalyst have slowed the marketization process.As a vital part of DBFC,anode catalyst is the key to obtaining high-performance fuel cells.Therefore,the design of an efficient low-cost anode catalyst become imperative to promote DBFC commercialization.The precious metal Au is corrosion-resistant and anti-oxidation,it has high selectivity to the hydrolysis reaction of BH₄^-and electro-oxidation（BOR）reaction（it has low hydrolysis reaction activity to BH₄^-）,so it becomes an ideal material for DBFC anode catalyst.In recent years,heteroatom-doped carbon materials have shown great brilliance in the field of electrocatalysis.Due to the difference in electronegativity between heteroatoms and carbon atoms,when heteroatoms are introduced into a carbon material,the electron cloud density of the carbon materials will be changed,and the active sites of the material will increase,which will lead to the change of chemical properties and enhance its adsorption to metal particles.In addition,transition metals have abundant reserves and low prices,and often exhibit unexpected synergistic catalytic effects with precious metals.Based on this,three different Au-based electrocatalysts were prepared by introducing N heteroatoms and transition metals into the carbon material,and used to catalyze BOR.The main research contents are as follows:Au/NC/C electrocatalyst was prepared by thermal polymerization and impregnation reduction method.The morphology and structure of Au/NC/C electrocatalyst were analyzed by SEM and XRD.The electrocatalytic activity of Au/NC/C catalyst for BOR was evaluated by electrochemical test and compared with that of Au/C catalyst.The results show that the direct catalytic oxidation activity of Au/NC/C for BH₄^-is higher than that of Au/C,and the oxidation current density reaches33.5 m A cm^-2.At the same time,the kinetics of electrocatalytic oxidation showed that the number of electrons transferred by Au/NC/C electrode in BOR reaction was higher than that by Au/C electrode.The Au/Co@NC/C catalyst was prepared by high-temperature pyrolysis of ZIF-67 precursor and impregnation reduction supported Au nanoparticles.The catalyst was characterized by TEM and XRD.Further electrochemical test studies have shown that Au/Co@NC/C catalyst performs better than Au/C catalyst in electrocatalytic oxidation of BOR,with the highest oxidation current density reaching 65.4 m A cm^-2,which is about 4 times that of Au/C electrode.In addition,Co@NC/C not only strengthens the precious metal catalyst,but also exhibits a certain catalytic effect on the hydrolysis reaction of BH₄^-.The nitrogen-doped Au/Cu Fe@NC/C composite catalyst was prepared by co-precipitation method and immersion reduction method.It was characterized by TEM and XRD,and its electrochemical behavior was tested and analyzed by CV and other electrochemical methods.The possible reasons for the improvement of the catalytic performance of the Au/Cu Fe@NC/C composite catalyst were analyzed.