Au as an efficient promoter for electrocatalytic oxidation of formic acid and carbon monoxide: a comparison between Pt-on-Au and PtAu alloy catalysts

The absence of unpaired d-electrons of gold leads to its lack of reactivity and paucity of catalytic activity. Synergistic activity of bimetallic PtAu has been proved, and its structure greatly influences on the electrocatalytic activity toward formic acid and carbon monoxide oxidation. Here, a comparison between Pt-modified Au (designated as Pt-on-Au) and PtAu alloy catalysts has been studied. The Pt-on-Au catalyst was prepared by electrodeposition of Pt on the pre-prepared Au, while PtAu alloy was obtained by co-electrodeposition. As a whole, both types of PtAu catalysts were found to be more active toward formic acid electrooxidation compared to pure Pt, exhibiting maximum activity on Pt-on-Au catalyst with Pt to Au atomic ratio of 1:10.22. Moreover, the Pt/Au atomic ratio directly relates to the oxidation pathway of formic acid and carbon monoxide oxidation. The results may be ascribed to much less CO_ads on the surface than single Pt catalyst due to the effect of Au nanoparticles. CO stripping voltammograms present the obvious variation between Pt-on-Au and PtAu alloy catalysts. Meanwhile, the electrocatalytic activities of bimetallic PtAu are evaluated by electrochemical impedance spectroscopy and Tafel analysis.