Bismuth has been observed to have a promotional effect on the catalytic properties of platinum, particularly in the selective oxidation of alcohols. Particularly, Bi on Pt can significantly enhance the catalytic activity of benzyl alcohol oxidation, producing industrially important products such as benzaldehyde and benzoic acid. A variety of mechanisms for this effect have been proposed. Among these are the ideas that formation of an alloy with Pt and Bi allows them to work synergistically, or that Bi inhibits the corrosion of Pt, enhancing its catalytic stability, which are not clear what mainly causes the Bi promotional effect. Herein, we present that the synergistic effect between Pt and Bi is supported by the Co-Operative Redox Enhancement (CORE) mechanism, which demonstrates synergistic redox coupling between two disparate metals by spontaneous polarization, using benzyl alcohol oxidation as a model reaction. The origin of the synergistic effect was investigated by employing a temperature- and pressure-controlled single chamber electrochemical cell, loaded with Bi2O2/C and Pt/C coated on carbon cloths as separate electrodes. Intriguingly, the two electrodes, when used in tandem, compared to Pt or Bi individually, resulted in a substantial increase in the conversion of benzyl alcohol to its oxidized forms: benzaldehyde and benzoic acid, analyzed by high performance liquid chromatography. More importantly, a short-circuit current, that accounts for 12.94.1 % of the total reaction conversion, was observed when utilizing the two electrodes without any external bias, strongly supporting the CORE mechanism for the Bi promotional effect. Stability tests showed that the Bi2O3/C + Pt/C mixture maintained CORE efficiency throughout 4 runs with the same catalysts, while conversion decreased steadily. While Pt/C on its own showed more stable conversion through 4 runs, it displayed a generally lower conversion rate of benzyl alcohol into its oxidation products. The results of the experiments conducted strongly support that the Bi promotional effect on Pt is at least partially rooted in the CORE mechanism.
