g-C₃N₄ Nanosheet Supported CuO Nanocomposites for the Electrochemical Carbon Dioxide Reduction Reaction

We have prepared CuO-derived electrocatalysts on a graphitic carbon nitride (g-C₃N₄) nanosheet support for the electrochemical carbon dioxide reduction reaction (CO₂RR). 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 Cu₂O/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 CH₄ and C₂H₄, and this might be due to the synergistic effects of Cu-g-C₃N₄ 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 CO₂RR product selection, and with precise controls of the experimental parameters, we believe that this will help to design and fabricate g-C₃N₄-supported catalyst systems with narrower product distribution.