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

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.