Electrochemical Synthesis of Rh Nanorods with High-Index Facets for the Oxidation of Formic Acid

Abstract

Noble metal catalysts play an important role in developing efficient fuel cells for commercial application at a large scale. Among them, Pt-group metal nanocatalysts enclosed with high-index facets have been expected to exhibit high electrocatalytic activity due to the high density of the low-coordination step and kink atoms exposed on the surface. Many good studies on Pt and Pd nanocatalysts enclosed with high-index facets have been reported while Rh nanocatalysts with a high-index facet have rarely been prepared. In this work, Rh nanorods with high-index facets (310) were synthesized successfully through repeated oxygenated species adsorption/desorption mediated by square wave potential (SWP). Electrochemical tests showed that Rh nanorods with high-index facets exhibited excellent electrocatalytic activity for the formic acid oxidation reaction (FAOR), and the peak current densities in positive scan of Rh nanorods (4.48 mA·cm–2) was 4.7 times higher than that of Rh black catalysts (0.95 mA·cm–2). In addition, the Rh nanorods could maintain higher current density than that of the Rh black catalysts throughout the time domain with potential held at 0.45 V, indicating that Rh nanorods had good stability for FAOR. The enhanced electrocatalytic performance of the Rh nanorods could be mainly ascribed to high-index facets with step and kink atoms, which could provide sufficient active sites for FAOR.