Stacking Fault Engineered Tensile‐Strained Delafossite CuAlO ₂ for CO ₂ Electroreduction to Deeply Reduced Products

ABSTRACT Precisely controlling the active center synergy of Cu‐based catalysts through material defect engineering is a crucial but challenging task for delicately tuning the selectivity of the CO 2 electroreduction reaction (eCO 2 RR) toward deeply reduced products of high economic value. In this work, delafossite‐structured CuAlO 2 catalysts featuring stabilized Cu + active sites via the tensile strain generated through stacking faults were constructed, and the strain‐engineered CuAlO 2 ‐800 exhibited enhanced activity toward deeply reduced products in eCO 2 RR, achieving a combined Faradaic efficiency for CH 4 and C 2 H 5 OH of 62.0% at −300 mA cm −2 . This selectivity profile is distinct from most reported Cu‐based catalysts. Combined experimental and theoretical investigations demonstrate that lattice strain upshifts the Cu d‐band center, strengthening the adsorption of key intermediates. The optimal Cu─O─Al spacing in the delafossite phase, combined with * H 2 O adsorbed on Al 3+ sites, promotes the hydrogenation of * CO to * CHO and ultimately to CH 4 , while simultaneously facilitating C 2 H 5 OH formation by tuning the * CH 2 CHO through hydrogen bonding. This work offers a new pathway for strain‐engineered design of Cu catalysts to enhance eCO 2 RR selectivity of high‐value products.