(427f) Achieving Complete Electrooxidation of Ethanol By Single Atomic Rh Decoration of Pt Nanocubes

Direct ethanol fuel cells are attracting growing attention as portable power sources due to their advantages such as higher mass-energy density than hydrogen and less toxicity than methanol. However, it is challenging to achieve the complete electrooxidation to generate 12 electrons per ethanol, resulting in a low fuel utilization efficiency. Herein, we report unalloyed single atomic, partially oxidized Rh on the Pt nanocube (NCs) surface as the electrocatalyst (Rh_atO-Pt NCs) to completely oxidize ethanol to CO₂ at a record-low potential of 0.35 V. Pt NCs decorated with partially oxidized Rh clusters (Rh_clO-Pt NCs), Pt NCs, and commercial Pt/C were also prepared for comparison. The catalyst prepared after loading Rh_atO-Pt NCs on a carbon support (Rh_atO-Pt NCs/C) demonstrated the highest EOR activity among all prepared electrocatalysts. At 0.75 V (versus reversible hydrogen electrode [RHE]), Rh_atO-Pt NCs/C showed 1.5-, 4.2-, and 11.4-fold higher current density than those of Rh_clO-Pt NCs/C, Pt NCs/C, and commercial Pt/C, respectively. Most importantly, the decoration of isolated Rh_atO rendered the Rh_atO-Pt NCs/C electrocatalyst capable to break the C–C bond of ethanol, resulting in >99.9% of CO₂ selectivity in a record-low onset and wide potential region (0.35 to 0.75 V). In situ X-ray absorption fine structure measurements and density functional theory calculations reveal that the single-atom Rh sites facilitate the C–C bond cleavage and the removal of the *CO intermediates. This work not only reveals the fundamental role of unalloyed, partially oxidized SAC in ethanol oxidation reaction but also offers a unique single-atom approach using low-coordination active sites on shape-controlled nanocatalysts to tune the activity and selectivity toward complicated catalytic reactions.