Lithium Vacancy-Tuned [CuO 4 ] Sites for Selective CO 2 Electroreduction to C 2+ Products.

Electrochemical CO 2 reduction to valuable multi-carbon (C 2+ ) products is attractive but with poor selectivity and activity due to the low-efficient CC coupling. Herein, a lithium vacancy-tuned Li 2 CuO 2 with square-planar [CuO 4 ] layers is developed via an electrochemical delithiation strategy. Density functional theory calculations reveal that the lithium vacancies (V Li ) lead to a shorter distance between adjacent [CuO 4 ] layers and reduce the coordination number of Li + around each Cu, featuring with a lower energy barrier for COCO coupling than pristine Li 2 CuO 2 without V Li . With the V Li percentage of ≈1.6%, the Li 2- x CuO 2 catalyst exhibits a high Faradaic efficiency of 90.6 ± 7.6% for C 2+ at -0.85 V versus reversible hydrogen electrode without iR correction, and an outstanding partial current density of -706 ± 32 mA cm -2 . This work suggests an attractive approach to create controllable alkali metal vacancy-tuned Cu catalytic sites toward C 2+ products in electrochemical CO 2 reduction.