Structure And Electro-catalytic Performance Study Of Platinum Alloy Nano-particles As Cathode Catalysts For Direct NaBH₄-H₂O₂Fuel Cells

Direct borohydride-hydrogen peroxide fuel cell (DBHFC) developed in recent years is a new type of fuel cell with higher open circuit voltage, higher energy density, and its raw materials are easier to store and transport. More importantly, DBHFC has attracted attention because it can be applied to underwater, space and some special environments. For this type of fuel cell, carbon supported Pt is widely used as cathode catalyst. But the limited resources and higher cost of Pt greatly limit the development of DBHFC. Finding a new type of catalyst, which can not only reduce the amount of Pt but also maintain the high catalytic activity to H2O2electroreduction, is important for promoting the DBHFC technology and commercial process.In this paper, we prepared Pt1/C(containing10%Pt), Pt2/C(20%Pt), Pt-Co/C and Pt-Mn/C(metal content=10%in either case) by the impregnation-reduction method. CV curves showed that Pt-Co/C has the highest peak potentials (0.435V) and the maximum peak current density (29.76mA/cm2) to H2O2electric catalytic reduction. XRD results show that Mn or Co replace a Pt atom in Pt cell unit and form solid solution alloy between Pt and Mn or Co. Compared with Pt1/C and Pt2/C, the diffraction peak intensity of Pt-Co/C and Pt-Mn/C is significantly weakened and widened. This indicated that adding Mn or Co is beneficial to reducing the catalyst crystallinity and increasing the active site in the catalysts. That is beneficial to electrochemical reduction reaction.In addition, CNTs was used in this paper as carrier of catalysts. CV curves showed that, compared with Pt-Ag/C and Pt-Co/C, the peak potentials of Pt-Ag/CNTs and Pt-Co/CNTs are lower, but their peak currents are higher. This may be determined by one-dimensional tubular structure and good electronic conductivity of CNTs.In order to solve the problem of hydrogen peroxide decomposition on the surface of DBHFC cathode catalyst, Pt-Co/CNTs、Pt-Ag/CNTs、Pt-Ag/C and Pt2/C were prepared, and were used as DBHFC cathode catalysts of four single cells respectively. The four cells discharged at a constant voltage for3600s. The actual discharge amount of the four cells can be calculated by the constant-voltage discharge curves. The consumption of hydrogen peroxide before and after discharging was measured by potassium permanganate titration, and then the theoretical discharge amount can be calculated by the consumption of hydrogen peroxide. The ratio between the actual and theoretical discharge amount is the utilization of hydrogen peroxide. Calculation results showed that the existence of Ag is beneficial to reducing H2O2decomposition, which can improve the utilization of H2O2.