Superexchange-stabilized long-distance Cu sites in rock-salt-ordered double perovskite oxides for CO₂ electromethanation.

Abstract

Cu-oxide-based catalysts are promising for CO₂ electroreduction (CO₂RR) to CH₄, 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 CO₂-to-CH₄ conversion. For the proof-of-concept catalyst of Sr₂CuWO₆, its corner-linked CuO₆ and WO₆ 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 CO₂RR, the Sr₂CuWO₆ exhibits significant improvements (up to 14.1 folds) in activity and selectivity for CH₄, together with well boosted stability, relative to a physical-mixture counterpart of CuO/WO₃. Moreover, the Sr₂CuWO₆ is the most effective Cu-based-perovskite catalyst for CO₂ methanation, achieving a remarkable selectivity of 73.1% at 400 mA cm^-2 for CH₄. 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.