Mechanistic Insights into Facet-Dependent Interfacial Chemistry Governing Ethanol Steam Reforming on Ni/CeO ₂

Ethanol steam reforming (ESR) enables renewable biomass-derived H 2 production but suffers from selectivity and deactivation challenges. While CeO 2 -supported metal catalysts are widely explored for ESR owing to strong metal–support interactions and inherent oxygen storage capacity, persistent ambiguities in facet-dependent performance arise from methodological constraints in decoupling intrinsic facet effects from metal particle size variations. By synthesizing morphology-controlled CeO 2 supports exposing distinct facets ({100}, {110}, {111}) and anchoring size-uniform Ni nanoparticles (∼2 nm), we decoupled facet contributions to reveal how facet-specific Lewis acidity governs OH* reactivity at Ni–CeO 2 interfaces. Combined kinetic assessments, in situ spectroscopy, and density functional theory identify α-C–H abstraction from CH 3 CH 2 O* by interfacial OH* as the kinetically relevant step, with acetate intermediates directly formed from CH 3 CH 2 O* (not acetaldehyde) facilitating C–C bond scission under steam-rich conditions. Ni supported on {100}-rich CeO 2 nanocubes enhances OH* reactivity via weakened Lewis acidity, lowering acetate formation barriers. This facet-modulated interfacial chemistry achieves 426 mmol g cat –1 h –1 H 2 formation rate and 72.1% CO 2 selectivity at 400 °C, surpassing literature benchmarks under comparable conditions. These findings elucidate how facet-dependent interfacial chemistry dictates ESR performance on Ni/CeO 2 catalysts, providing mechanistic insights beyond conventional oxygen storage capacity correlations.