Boosting ethanol electrooxidation at RhBi alloy and Bi2O3 composite surfaces in alkaline media

Abstract

As a promising alternative to Pd and Pt catalysts, Rh has been found to be an effective catalyst for the ethanol oxidation reaction (EOR). However, Rh-based catalysts can only show a limited EOR mass activity, making them impractical for Direct Ethanol Fuel Cells (DEFCs). Thus, well-designed composites of RhBi alloy and freestanding surface Bi₂O₃ (RhBi–Bi₂O₃) are prepared, directed by the Langmuir–Hinshelwood mechanism to achieve two effects simultaneously as follows: weakening the surface adsorption of poisonous intermediates by Bi addition to downshift the d-band center of Rh, and enriching the supply of oxygenated species by freestanding surface Bi₂O₃ species. Indeed, the optimal RhBi–Bi₂O₃ catalysts show superior EOR mass activity of up to ca. 5000 mA mg⁻¹ Rh, which is ca. 80 times and 2.5 times higher than that of pristine Rh and commercial Pd/C catalyst, respectively. Meanwhile, it also exhibits long-term durability, ca. 53.7% of faradaic current remains even after a 10 000 second-long measurement. This work might offer new opportunities for the design of EOR electrocatalysts.