Symmetry-Differentiated Oxygen-Vacancy Motifs Regulate Au–CeOx Interfaces for Selective Photocatalytic Ethane Production from CO2

Abstract

Steering CO₂ photoreduction toward C₂ hydrocarbons remains challenging because of the sluggish multielectron/proton-transfer kinetics and the high energetic demand for C–C coupling. Herein, we report a flame-spray-pyrolysis strategy to construct Au–CeO_x nanostructures featuring coexisting symmetric oxygen vacancies (Ce–O_v–Ce) and symmetry-broken oxygen vacancy (Au–O_v–Ce) motifs at the Au–CeO_x interface. The symmetric Ce–O_v–Ce sites provide favorable adsorption environments for CO₂ activation, whereas the symmetry-broken Au–O_v–Ce sites induce interfacial electron redistribution and promote electron enrichment. The cooperative interaction between these two vacancy configurations shifts the reaction route from *CO desorption toward deep hydrogenation and *CH₃-mediated C–C coupling. As a result, the optimized Au–CeO_x–SAO_v catalyst achieves a C₂H₆ production rate of 2581 μmol g_Au^–1 h^–1 with a selectivity of 88.14% and an electron utilization rate of 41.22 mmol g_Au^–1 h^–1 in photocatalytic CO₂ reduction with H₂O. Mechanistic studies suggest that the symmetry-broken Au–O_v–Ce sites stabilize hydrogenated C₁ intermediates and lower the energetic requirement for coupling two *CH₃ species. This work establishes symmetry-differentiated oxygen-vacancy engineering as an effective strategy for directing multielectron CO₂ photoreduction toward C₂ hydrocarbons.