Which Catalyst Exhibits Superior C–C Bond Cleavage Ability in Ethanol Electrooxidation: An In-Situ ATR-SEIRAS Investigation

Platinum-group metals (PGMs) are among the most active electrocatalysts for the ethanol oxidation reaction. Nevertheless, their intrinsic efficacy in C-C bond scission remains contentious, and unequivocal molecular-level evidence is still wanting. To approach it, we employed in situ electrochemical attenuated total-reflection surface-enhanced infrared spectroscopy under both conventional and thin-layer flow cells as the main method, for the first time, by using the relative population ratio of COad (η) as the descriptor on the identical electrode, to rank the C-C bond cleavage activity of the four PGMs as Ir > Rh > Pd > Pt in alkaline media from both thermodynamic and kinetic perspectives. Moreover, the maximized C-C bond cleavage activity was found at 0.20 ∼ 0.30 V for Pt, Rh, and Ir and at 0.40 ∼ 0.50 V for Pd. This work develops a molecular-level strategy for probing catalytic processes through a simple descriptor and might offer a fresh perspective for investigating surface reaction pathways.