g -C 3 N 4 Nanosheet Supported CuO Nanocomposites for the Electrochemical Carbon Dioxide Reduction Reaction.

We have prepared CuO-derived electrocatalysts on a graphitic carbon nitride ( g -C 3 N 4 ) nanosheet support for the electrochemical carbon dioxide reduction reaction (CO 2 RR). Highly monodisperse CuO nanocrystals made by a modified colloidal synthesis method serve as the precatalysts. We use a two-stage thermal treatment to address the active site blockage issues caused by the residual C18 capping agents. The results show that the thermal treatment effectively removed the capping agents and increased the electrochemical surface area. During the process, the residual oleylamine molecules incompletely reduced CuO to a Cu 2 O/Cu mixed phase in the first stage of thermal treatment, and the following treatment in forming gas at 200 °C completed the reduction to metallic Cu. The CuO-derived electrocatalysts show different selectivities over CH 4 and C 2 H 4 , and this might be due to the synergistic effects of Cu- g -C 3 N 4 catalyst-support interaction, varied particle sizes, dominant surface facets, and catalyst ensemble. The two-stage thermal treatment enables sufficient capping agent removal, catalyst phase control, and CO 2 RR product selection, and with precise controls of the experimental parameters, we believe that this will help to design and fabricate g -C 3 N 4 -supported catalyst systems with narrower product distribution.