Electrochemical CO2 reduction to produce valuable C2 products is attractive but still suffers with relatively poor selectivity and stability at high current densities, mainly due to the low efficiency in the coupling of two *CO intermediates. Herein, it is demonstrated that high‐density nitrogen vacancies formed on cubic copper nitrite (Cu3Nx) feature as efficient electrocatalytic centers for CO–CO coupling to form the key OCCO* intermediate toward C2 products. Cu3Nx with different nitrogen densities are fabricated by an electrochemical lithium tuning strategy, and density functional theory calculations indicate that the adsorption energies of CO* and the energy barriers of forming key C2 intermediates are strongly correlated with nitrogen vacancy density. The Cu3Nx catalyst with abundant nitrogen vacancies presents one of the highest Faradaic efficiencies toward C2 products of 81.7 ± 2.3% at −1.15 V versus reversible hydrogen electrode (without ohmic correction), corresponding to the partial current density for C2 production as −307 ± 9 mA cm−2. An outstanding electrochemical stability is also demonstrated at high current densities, substantially exceeding CuOx catalysts with oxygen vacancies. The work suggests an attractive approach to create stable anion vacancies as catalytic centers toward multicarbon products in electrochemical CO2 reduction.

Electrochemical CO2 reduction to valuable multi‐carbon (C2+) products is attractive but with poor selectivity and activity due to the low‐efficient CC coupling. Herein, a lithium vacancy‐tuned Li2CuO2 with square‐planar [CuO4] layers is developed via an electrochemical delithiation strategy. Density functional theory calculations reveal that the lithium vacancies (VLi) lead to a shorter distance between adjacent [CuO4] layers and reduce the coordination number of Li+ around each Cu, featuring with a lower energy barrier for COCO coupling than pristine Li2CuO2 without VLi. With the VLi percentage of ≈1.6%, the Li2−xCuO2 catalyst exhibits a high Faradaic efficiency of 90.6 ± 7.6% for C2+ 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 C2+ products in electrochemical CO2 reduction.

The electrochemical CO2 reduction to CH4 is a promising approach for producing highly specific combustion fuel but has relatively poor selectivity and activity at high‐current‐density electrolysis. In this work, ultrathin CuGaO2 nanosheets with highly exposed single‐interlayered Cu edges are synthesized via an induced anisotropic growth strategy. Density functional theory calculations indicate that the exposed single‐interlayered Cu(I) edges on the (001) surface of CuGaO2 present a high‐density of single‐atomic Cu sites, which feature excellent CO2 electroreduction catalytic activity toward CH4. The CuGaO2 nanosheet catalysts exhibit efficient and stable CO2‐to‐CH4 electroreduction with Faradaic efficiency (FECH4) of 71.7% at a high current density of –1 A cm−2, corresponding to a superior CH4 partial current density of 717 ± 33 mA cm−2. This work suggests an attractive design strategy for tuning both the crystal facets and Cu–Cu distance to promote the CH4 electrosynthesis at high‐current‐density CO2 reduction.

Electrocatalytic CO2 reduction features a promising approach to realize carbon neutrality. However, its competitiveness is limited by the sluggish oxygen evolution reaction (OER) at anode, which consumes a large portion of energy. Coupling value‐added anodic reactions with CO2 electroreduction has been emerging as a promising strategy in recent years to enhance the full‐cell energy efficiency and produce valuable chemicals at both cathode and anode of the electrolyzer. This review briefly summarizes recent progresses on the electrocatalytic CO2 reduction, and the economic feasibility of different CO2 electrolysis systems is discussed. Then a comprehensive summary of recent advances in the coupled electrolysis of CO2 and potential value‐added anodic reactions is provided, with special focus on the specific cell designs. Finally, current challenges and future opportunities for the coupled electrolysis systems are proposed, which are targeted to facilitate progress in this field and push the CO2 electrolyzers to a more practical level.

The electrochemical CO2 reduction to CH4 has been extensively demonstrated, but still suffers from relatively poor activity and requires high overpotentials especially at large electrolysis rates. Perovskite oxides (AxByO) are one type of promising electrocatalyst for the CO2 reduction due to their tunable electronic structures. In this work, a Ca2CuO3 perovskite oxide catalyst is developed with alkaline‐earth A‐sites, featuring an inherently strong basic strengthand outstanding capability for CO2 adsorption, as well as the undercoordinated Cu sites generated through partial surface Ca2+ cation leaching. The Ca2CuO3 catalyst exhibitsa high partial current density of 517 ± 23 mA cm−2 for producing CH4 at a low applied potential of −0.30 V versus reversible hydrogen electrode, which further reached to a peak value of 1452 ± 156 mA cm−2. Density functional calculations show that the undercoordinated Cu sites allowed to promote the hydrogenation of *CO and subsequent *CHO intermediates, thus leading to the high CH4 activity. This work suggests an attractive design strategy for tuning the A‐sites in perovskite oxides to realize high‐rate CO2‐to‐CH4 electrosynthesis with low overpotentials.