Study On The Microstructure And Properties Of Co-Sn Based Anode Catalysts For Direct Borohydride Fuel Cells

The anode catalyst of direct borohydride fuel cell（DBFC）is one of the key factors determining the performance of DBFC.In the anodic electrochemical oxidation process of BH₄^-,hydrolytic reaction will affect the efficiency of the cell,and hydrogen generation will bring safety risks.Therefore,the anodic catalyst used should theoretically have high catalytic activity,low cost and can inhibit borohydride hydrolysis.Co₃O₄has attracted much attention due to its high theoretical specific capacitance and excellent stability.As a catalyst,Sn O₂has the advantages of abundant reaction sites and high electrochemical activity.The resistivity of Sn O is low and its nanometer thin layer has a large layer spacing.In this paper,hydrothermal method and electrodeposition method will be used to synthesize Co-Sn-based alloy for DBFC anode catalyst,in the hope of obtaining catalyst with better catalytic performance,and through Ag sensitization and P doping to modify the complex,to inhibit the hydrolysis of borohydride,the main research content and results of this paper are as follows:（1）Co-Sn alloy catalysts were prepared on nickel foam by hydrothermal method and electrodeposition method respectively.The electrochemical properties and catalytic activity of the two catalysts were studied by physical characterization,electrochemical test and battery test.The morphology of the two synthesis methods is quite different.XPS analysis map provides evidence for the existence of each element,and illustrates the existence of the chemical states and atomic ratio of each element.Electrochemical test results showed that Co-Sn/hydrothermal catalyst showed the best catalytic activity,and the maximum power density of DBFC battery was 86 m W·cm^-2at 160 m A·cm^-2.The maximum power density of DBFC was 73 m W·cm^-2at 140 m A·cm^-2.The existence of hydrolysis reaction affects the efficiency of the battery.（2）Co-Sn@Ag catalyst was prepared by hydrothermal method and electrodeposition method respectively by soaking nickel foam in silver nitrate solution to avoid photosensitization.The inhibition effect of Ag sensitization on KBH₄hydrolysis and catalytic KBH₄electrooxidation was studied.According to the physical characterization,the grains of both catalysts are nanoscale.According to the electrochemical performance test,Co-Sn@Ag/hydrothermal LSV peak current is higher,CV curve current window is larger,that is,the catalytic activity is better than Co-Sn@Ag/electrodeposition,and electrooxidation reaction is more likely to occur.It also indicates that both catalysts have a certain catalytic effect on the oxidation of BH₄^-.The maximum power density of the battery assembled with Co-Sn@Ag/hydrothermal anode catalyst reaches 88 m W·cm^-2,and the specific capacity is large and stable,which is 2790 m Ah·g^-1.The best catalytic activity was obtained when the hydrothermal temperature was 180℃.It is speculated that the Co-Sn bimetallic complex plays a synergistic catalytic role with Ag,and Ag has a certain inhibitory effect on the hydrolysis of BH₄^-.（3）Because the functional groups containing P can enhance the charge storage and transfer ability of the catalyst,thus improving the conductivity.In this chapter,electrodeposition and hydrothermal processes were used to prepare three kinds of catalysts,namely Co-Sn-P/electrodeposition,Co-Sn-Ag/electrodeposition and Co-Sn-P/hydrothermal,respectively.According to CV curve and LSV curve,the three catalysts had consistent electrochemical behavior,and the catalytic activity of Co-Sn-Ag/electrodeposition was slightly lower.Co-Sn-P/hydrothermal has higher electrocatalytic activity.Co-Sn-P/hydrothermal catalyzed DBFC has an open-circuit voltage of 1.04 V and a maximum power density of 94 m W·cm^-2at a current density of 200 m A·cm^-2.The improvement of each data indicates that BH₄^-is more fully catalyzed,so P doping has a certain inhibitory effect on the hydrolysis of BH₄^-.