Revisiting the Acetaldehyde Oxidation Reaction on a Pt Electrode by High-Sensitivity and Wide-Frequency Infrared Spectroscopy
Xian‐Yin Ma, Chen Ding, Hong Li, Kun Jiang, Sai Duan, Wen–Bin Cai
Abstract
High-sensitivity and wide-frequency attenuated total reflection surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS) is highly demanded in unraveling electrocatalytic processes at the molecular level. In this work, an in situ ATR-SEIRAS technique incorporating a micromachined Si wafer window, p-polarized infrared radiation, and isotope labeling is extended to revisit the acetaldehyde oxidation reaction (AOR) on a Pt electrode in an acidic medium. New spectral features in the fingerprint region are detected, including ω(C–H) at 1078 cm–1 and νas(C–C–O) at 919 cm–1 for adsorbed acetaldehyde and δ(O–C–O) at 689 cm–1 for adsorbed acetate, besides the other enhanced and clearly discriminated spectral signals at higher frequencies. Time-evolved and potential-dependent ATR-SEIRAS measurements together with advanced density functional theory calculations considering the coadsorption of CO and C2 species enable clarification of the structures and roles of surface C2 intermediates (η1(C)-acetyl and η1(H)-acetaldehyde), as reflected by the two bands at 1630 and 1663 cm–1, respectively, leading to updated pathways for the AOR on a Pt electrode.