Pyrolysis-free synthesis of a high-loading single-atom Cu catalyst for efficient electrocatalytic CO 2 -to-CH 4 conversion.

Electrocatalytic CO 2 -to-CH 4 conversion provides a promising means of addressing current carbon resource recycling and intermittent energy storage. Cu-based single-atom catalysts have attracted extensive attention owing to their high intrinsic activity toward CH 4 production; however, they suffer from uncontrollable metal loading and aggregation during the conventional pyrolysis process of carbon-based substrates. Herein, we developed a pyrolysis-free method to prepare a single-atom Cu catalyst anchored on a formamide polymer substrate with a high loading amount and well atomic dispersion through a mild polycondensation reaction. Owing to the isolation of copper active sites, efficient CO 2 -to-CH 4 conversion is achieved over the single-atom Cu catalyst, along with the significant suppression of C-C coupling. As a result, the optimal single-atom catalyst with 5.87 wt% of Cu offers high CH 4 faradaic efficiencies (FEs) of over 70% in a wide current density range from 100 to 600 mA cm -2 in the flow cell, together with a maximum CH 4 partial current density of 415.8 mA cm -2 . Moreover, the CH 4 FE can reach 74.2% under optimized conditions in a membrane electrode assembly electrolyzer. This work provides new insights into the subtle design of highly efficient electrocatalyst for CO 2 reduction.