Highly selective conversion of carbon dioxide to methane by copper single atom electrocatalysts

Electrocatalytic carbon dioxide (CO2) reduction into high-value chemicals is one of the important solutions to the greenhouse effect and energy crisis. However, the slow kinetic process of eight electrons requires the development of efficient catalysts to improve the yields. Single atom catalysts (SACs) with high activity and selectivity have become an emerging research frontier in the field of heterogeneous catalysis. Herein, a catalyst comprised of Cu single atoms loaded on carbon substrate (Cu-NC) is developed for highly selective electrocatalytic reduction of CO2 to methane (CH4). The optimal catalyst (Cu-NC-1-4) exhibits a faradaic efficiency (FE) of over 50% for CH4 within a wide potential window from -1.3 V to -1.8 V (vs. RHE) and the highest FE of CH4 is up to 67.22% at -1.6 V (vs. RHE). Meanwhile, the product selectivity of CH4 among all the carbon products reaches 93.00%, and the activity decay can be negligible via the 70-hour-stability-test. The existence of atomic dispersed Cu-N3 sites was verified by high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) and X-ray absorption near edge structure (XANES). Density functional theory (DFT) calculations show that the effective adsorption of the key intermediate *CO on Cu-N3 sites prompts the generation of CH4.