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.
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