Study On Electrochemical Behavior Of Pd-based Anode Catalysts Towards Sodium Borohydride Electrooxidation

Direct borohydride fuel cell?DBFC? as a new type of chemical power source is received extensive attention of the researchers for many advantages, such as easy storage and transportation of fuel, no CO poisoning of anode catalyst, high theoretical open circuit voltage, higher power density and low operating temperature. DBFC has broad application propects in the field of portable power supply, however it need further study to achieve the commercialization. How to anode catalyst with high catalytic activity, low cost and high selectivity, thereby increasing the sodium borohydride electrooxidation reaction kinetic speed and reducing the extent of the hydrolysis reaction, is main goal of DBFC anode catalyst research and is also the key issue to achieve DBFC commercialization. Aiming at the existing problems of DBFC, Pd-Ag/C and Pd-Fe/C catalysts with different atomic ratio were prepared and their electrochemical behaviors of sodium borohydride electrooxidation reaction were studied. The main contents are as follows:1. Pd/C catalyst was prepared using chemical reduction method. The effects of scan rate, the composition of electrolyte, temperature, catalyst carrier, and preparation method of catalyst on the electrochemical behavior of sodium borohydride electrooxidation at Pd/C electrode were investigated by cyclic voltammetry and chronoamperometry. It showd that their effects on the sodium borohydride electrooxidation reaction kinetic speed and the mechanism of sodium borohydride electrooxidation reaction in varying degrees.2. Pd/C, Pd₆₇Ag₃₃/C, Pd₅₀Ag₅₀/C and Pd₃₃Ag₆₇/C catalysts were prepared respectively by chemical reduction method at room temperature, and their effects on the electrochemical behavior of sodium borohydride electrooxidation were investigated. The results showed that the Ag doping with an appropriate amount could effectively reduce the cost of catalysts, have higher catalytic activity and the number of transferred electron, which was beneficial to the improvement of the fuel efficiency. The metal nanoparticles of prepared catalysts evenly dispersed on the surface of carbon black. Pd-Ag alloy was formed with the metallic Ag getting into the crystal lattice of Pd, which made the crystal structure of Pd changed. The grain size and the content of PdOads were important factors that can affect the catalytic activity of Pd-Ag/C.3. Pd/C, Pd₆₇Fe₃₃/C, Pd₅₀Fe₅₀/C, Pd₃₃Fe₆₇/C and Fe/C catalysts were prepared respectively by chemical reduction method at 80?. It showed that the peak current per unit Pd mass of Pd-Fe/C were significantly higher than that of Pd/C. the activity and stability of Pd₃₃Fe₆₇/C catalyst were high, and the Fe doping with a moderate amount was beneficial to increase the number of transferred electrons. There was a certain amount of Fe₃O₄ in prepared Pd-Fe/C catalysts. The metal nanoparticles of prepared Pd₃₃Fe₆₇/C catalyst evenly dispersed on the surface of carbon black. it contained Pd, Fe, O and C four elements, and the Fe to Pd ratio was 2.02:1, which was basic coincident with the theoretic value. The Pd of prepared Pd₃₃Fe₆₇/C catalyst mainly existed in Pd⁰.