Co-deposits of Pt and Bi on Au disk toward formic acid oxidation

Presented in this work is an investigation of co-deposits of Pt and Bi on Au disk (Pt-Bi/Au) toward formic acid oxidation (FAO) using voltammetry and X-ray photoelectron spectroscopy (XPS). The co-deposits of Pt and Bi on Au were prepared using an irreversible method in a mixed solution of Pt ion (1 mM) and Bi ion (5 mM), and the amount of co-deposits was controllable by the number of deposition cycles. The voltammetric studies revealed that the Pt-Bi/Au surfaces presented the characteristics of Pt, Bi, and Au depending on the number of deposition cycles. A detailed analysis of semi-quantitative results of XPS combined with hydrogen coverage on Pt and covered fraction of Au surface suggested two aspects of Pt-Bi co-deposits. One is that during co-adsorption, Bi adsorbing with a low efficiency enhanced irreversible adsorption of Pt. The other is that the Pt-Bi co-deposits would be an alloy of Pt-Bi when the Pt amount was low or Pt deposits enriched with Bi in surface regions when the Pt amount was high. The best FAO catalytic efficiency among the investigated Pt-Bi/Au surfaces was ~ 14 mA/cm2, which was higher than that of plain Pt deposits on Au (~ 6 mA/cm2) and comparable to that of sequentially prepared Bi-modified Pt deposits on Au (Bi/Pt/Au, ~ 20 mA/cm2). Because of a similarity in compositions and catalytic performances of the best Pt-Bi/Au and Bi/Pt/Au, the preparation procedure was concluded not to be critical so that the co-deposition method was more beneficial in terms of the number of deposition cycles in manufacturing electrocatalysts toward FAO.