Lithiation‐Enabled High‐Density Nitrogen Vacancies Electrocatalyze CO<sub>2</sub> to C<sub>2</sub> Products
Peng Chen, Gan Luo, Zikai Xu, Shuai Yan, Junbo Zhang, Menghuan Chen, Linping Qian, Wei Wei, Qing Han, Gengfeng Zheng
Abstract
Abstract Electrochemical CO 2 reduction to produce valuable C 2 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 (Cu 3 N x ) feature as efficient electrocatalytic centers for CO–CO coupling to form the key OCCO* intermediate toward C 2 products. Cu 3 N x 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 C 2 intermediates are strongly correlated with nitrogen vacancy density. The Cu 3 N x catalyst with abundant nitrogen vacancies presents one of the highest Faradaic efficiencies toward C 2 products of 81.7 ± 2.3% at −1.15 V versus reversible hydrogen electrode (without ohmic correction), corresponding to the partial current density for C 2 production as −307 ± 9 mA cm −2 . An outstanding electrochemical stability is also demonstrated at high current densities, substantially exceeding CuO x catalysts with oxygen vacancies. The work suggests an attractive approach to create stable anion vacancies as catalytic centers toward multicarbon products in electrochemical CO 2 reduction.