Photochemical H2 dissociation for nearly quantitative CO2 reduction to ethylene.

Producing olefins by carbon dioxide (CO2) hydrogenation is a long-standing goal. The usual products are multicarbon mixtures because the critical step of heterolytic hydrogen (H2) dissociation at high temperatures complicates selectivity control. In this study, we report that irradiating gold-titanium dioxide at 365 nanometers induces heterolytic H2 dissociation at ambient temperature. This process likely relies on interfacial electric dipoles from photogenerated electrons and holes situated on the metallic gold nanoparticles and interfacial gold-oxygen-titanium scaffolds. The heterolytic H2 dissociation is further promoted by light-induced coating of gold nanoparticles with a titanium oxide layer. The resulting nucleophilic hydrogen species reduce CO2 to ethane in >99% yield under light irradiation in a flow apparatus. Furthermore, cascading with a subsequent photocatalytic ethane dehydrogenation generates ethylene in >99% yield over 1500 hours of irradiation.