Protecting Copper Oxidation State via Intermediate Confinement for Selective CO 2 Electroreduction to C 2+ Fuels

Selective and efficient catalytic conversion of carbon dioxide (CO 2 ) into value-added fuels and feedstocks provides an ideal avenue to high-density renewable energy storage. An impediment to enabling deep CO 2 reduction to oxygenates and hydrocarbons (e.g., C 2+ compounds) is the difficulty of coupling carbon–carbon bonds efficiently. Copper in the +1 oxidation state has been thought to be active for catalyzing C 2+ formation, whereas it is prone to being reduced to Cu 0 at cathodic potentials. Here we report that catalysts with nanocavities can confine carbon intermediates formed in situ, which in turn covers the local catalyst surface and thereby stabilizes Cu + species. Experimental measurements on multihollow cuprous oxide catalyst exhibit a C 2+ Faradaic efficiency of 75.2 ± 2.7% at a C 2+ partial current density of 267 ± 13 mA cm –2 and a large C 2+ -to-C 1 ratio of ∼7.2. Operando Raman spectra, in conjunction with X-ray absorption studies, confirm that Cu + species in the as-designed catalyst are well retained during CO 2 reduction, which leads to the marked C 2+ selectivity at a large conversion rate.