Fabrication of Ag/Au/Pt Composite Catalysts and Their Electrocatalytic Oxidation for Formic Acid

Ag/Au/Pt composite catalyst has been fabricated by chemical and electrochemical methods. The catalyst is fabricated by the electrodeposition of 100 nm Ag nanoparticle, then Au is deposited by chemical reduction, and Pt is electrodeposited finally, the quantity of Au and Pt is reduced. The samples have been characterized by scanning electron microscopy (SEM), X-ray energy dispersive spectroscopy (EDX) and X-ray diffraction (XRD) techniques. In addition, the electrocatalytic performance of composite electrode materials is measured by cyclic voltammetry (CV) towards formic acid oxidation. The results demonstrate that the as-prepared Ag/Au/Pt composite catalyst with low Pt loading (0.71 mu g/cm(2)) shows much higher catalytic activity than that of the same amount of pure Pt catalyst towards formic acid electrooxidation, and the current density of direct oxidation for formic acid reaches 4541.42 mA/mg. On the other hand, the content of Pt has a significant influence on formic acid oxidation path. It is found that formic acid electrooxidation on the Ag/Au/Pt composite catalyst mainly follows the direct oxidation path only when the atomic ratio of Pt : Au is less than 1 : 10. The enhanced performance is mainly due to the increase of electrochemical active surface area (EASA) through CVs in H2SO4 solution. Moreover, the Ag/Au/Pt composite catalyst exhibits greater poisoning tolerance than that of pure Pt during formic acid electrooxidation, shown in the results of chronoamperometre (CA) measurement. The stability of composite catalyst is evaluated via recording the CV scans of 100 cycles of electrodes towards formic acid oxidation. At the 100th cycle, the current density of Ag/Au/Pt electrode just decreases 2.29%, which is far lower compared with the other electrodes. The CO stripping voltammogram in acid medium is recorded as well. The results show clearly that the CO stripping peak position of composite catalyst shifts negatively compared with that of the pure Pt catalyst in the mass. When the atomic ratio of Pt : Au is 1 : 6.0, the composite catalyst presents lowest peak potential for CO electrooxidation.