Improved direct electrooxidation of formic acid by increasing Au fraction on the surface of PtAu alloy catalyst with heat treatment

Highlights: ► PtAu/C alloy catalyst is obtained by microwave-assisted polyol reduction method. ► Heat treatment is performed successfully to increase Au fraction on PtAu surface. ► The direct electrooxidation of HCOOH is improved on the heat treated catalyst. ► Both activity and durability of heat treated catalyst are improved greatly. ► The superior performance of heat treated catalyst is attributed to the improved ensemble effect resulted from the increased interrupting Pt sites in the presence of more Au atoms on PtAu surface. - Abstract: The PtAu/C alloy catalyst is firstly synthesized by the co-reduction of both metal precursors under microwave conditions and then heat-treated to enable the migration of Au atoms to the exterior surface of the obtained PtAu/C catalyst. The bulk crystallite structures and the surface Au contents of PtAu/C catalysts are characterized by X-ray diffraction and X-ray photoelectron spectroscopy, respectively. The electrocatalytic activity and durability measurements exhibit the superior catalytic performance of PtAu/C catalysts over that of Pt/C catalyst on formic acid electrooxidation. Moreover, the initial and final activity after 3600 s reaction of the heat-treated PtAu/C alloy catalyst is two and five times as high as that of the untreated PtAu/C catalyst. The performance enhancement of the PtAu/C catalysts is discussed in terms of the electronic effect and ensemble effect.