Symmetry-Differentiated Oxygen-Vacancy Motifs Regulate Au–CeO x Interfaces for Selective Photocatalytic Ethane Production from CO 2

Steering CO 2 photoreduction toward C 2 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 CO 2 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 *CH 3 -mediated C–C coupling. As a result, the optimized Au–CeO x –SAO v catalyst achieves a C 2 H 6 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 CO 2 reduction with H 2 O. Mechanistic studies suggest that the symmetry-broken Au–O v –Ce sites stabilize hydrogenated C 1 intermediates and lower the energetic requirement for coupling two *CH 3 species. This work establishes symmetry-differentiated oxygen-vacancy engineering as an effective strategy for directing multielectron CO 2 photoreduction toward C 2 hydrocarbons.