Superexchange-stabilized long-distance Cu sites in rock-salt-ordered double perovskite oxides for CO electromethanation.

Cu-oxide-based catalysts are promising for CO electroreduction (CORR) to CH, but suffer from inevitable reduction (to metallic Cu) and uncontrollable structural collapse. Here we report Cu-based rock-salt-ordered double perovskite oxides with superexchange-stabilized long-distance Cu sites for efficient and stable CO-to-CH conversion. For the proof-of-concept catalyst of SrCuWO, its corner-linked CuO and WO octahedral motifs alternate in all three crystallographic dimensions, creating sufficiently long Cu-Cu distances (at least 5.4 Å) and introducing marked superexchange interaction mainly manifested by O-anion-mediated electron transfer (from Cu to W sites). In CORR, the SrCuWO exhibits significant improvements (up to 14.1 folds) in activity and selectivity for CH, together with well boosted stability, relative to a physical-mixture counterpart of CuO/WO. Moreover, the SrCuWO is the most effective Cu-based-perovskite catalyst for CO methanation, achieving a remarkable selectivity of 73.1% at 400 mA cm for CH. Our experiments and theoretical calculations highlight the long Cu-Cu distances promoting *CO hydrogenation and the superexchange interaction stabilizing Cu sites as responsible for the superb performance.