Superexchange-stabilized long-distance Cu sites in rock-salt-ordered double perovskite oxides for CO 2 electromethanation.

Cu-oxide-based catalysts are promising for CO 2 electroreduction (CO 2 RR) to CH 4 , 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 2 -to-CH 4 conversion. For the proof-of-concept catalyst of Sr 2 CuWO 6 , its corner-linked CuO 6 and WO 6 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 CO 2 RR, the Sr 2 CuWO 6 exhibits significant improvements (up to 14.1 folds) in activity and selectivity for CH 4 , together with well boosted stability, relative to a physical-mixture counterpart of CuO/WO 3 . Moreover, the Sr 2 CuWO 6 is the most effective Cu-based-perovskite catalyst for CO 2 methanation, achieving a remarkable selectivity of 73.1% at 400 mA cm -2 for CH 4 . 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.