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

Selective and efficient catalytic conversion of carbon dioxide (CO) into value-added fuels and feedstocks provides an ideal avenue to high-density renewable energy storage. An impediment to enabling deep CO reduction to oxygenates and hydrocarbons (e.g., C 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 formation, whereas it is prone to being reduced to Cu at cathodic potentials. Here we report that catalysts with nanocavities can confine carbon intermediates formed , which in turn covers the local catalyst surface and thereby stabilizes Cu species. Experimental measurements on multihollow cuprous oxide catalyst exhibit a C Faradaic efficiency of 75.2 ± 2.7% at a C partial current density of 267 ± 13 mA cm and a large C-to-C 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 reduction, which leads to the marked C selectivity at a large conversion rate.