Screening Efficient C–N Coupling Catalysts for Electrosynthesis of Acetamide and Output Ammonia through a Cascade Strategy of Electrochemical CO2 and N2 Reduction Using Cu-Based Nitrogen–Carbon Nanosheets

Due to the limitation of the high-value-added products obtained from electrocatalytic CO 2 reduction within an acid environment, introducing additional elements can expand the diversity of the products obtained during the CO 2 reduction reaction (CO 2 RR) and nitrogen reduction reaction (NRR). Thus, coelectroreduction of CO 2 and N 2 is a new strategy for producing acetamide (CH 3 CONH 2 ) via both C–C and C–N bond coupling using Cu-based nitrogen–carbon nanosheets. CO 2 can reduce to CO, and a key ketene (*C═C═O) can be generated from *CO*CO dimerization; this ketene is postulated as an intermediate in the formation of acetamide. However, most studies focus on promoting the C–C bond formation. Here, we propose that C–N bond coupling can form acetamide through the interaction of *C═C═O with NH 3 . The acetamide is formed via a nucleophilic attack between *NH 3 and the *C═C═O intermediate. The C–N coupling mechanism was successfully applied to expand the variety of nitrogen-containing products obtained from CO 2 and N 2 coreduction. Thus, we successfully screened Cu 2 -based graphite and Cu-based C 3 N 4 as catalysts that can produce C 2+ compounds by integrating CO dimerization with acetamide synthesis. In addition, we observed that Cu 2 -based C 2 N and Cu-based C 3 N 4 catalysts are suitable for the NRR. Cu-based C 3 N 4 showed high CO 2 RR and NRR activities with small negative limiting potential (U L ) values of −0.83 and −0.58 V compared to those of other candidates, respectively. The formation of *COHCOH from *COHCO was considered the rate-determining step (RDS) during acetamide electrosynthesis. The limiting potential value of Cu 2 -based C 2 N was only −0.46 V for NH 3 synthesis, and the formation of *NNH was via the RDS via an alternating path. The adsorption energy difference analysis both CO 2 and N 2 compare with the hydrogen evolution reaction (HER), suggesting that Cu 2 -based C 2 N exhibited the highest CO 2 RR and NRR selectivity among the 13 analyzed catalysts. The results of this study provide innovative insights into the design principle of Cu-based nitrogen–carbon electrocatalysts for generating highly efficient C–N coupling products.