Photocatalytic conversion of gas phase carbon dioxide by graphitic carbon nitride decorated with cuprous oxide with various morphologies

Submicron cuprous oxide (Cu2O) crystals with various morphologies were successfully fabricated and incorporated with graphitic carbon nitride (gCN) to evaluate their activity for gas phase CO2 photoreduction under visible-light illumination. Both the morphology of Cu2O and the composition of copper species were tunable and were significantly affected by the presence of gCN. The morphology of Cu2O influenced the band structure and optical property, as well as the efficiency of photo-induced charge transfer within each sample. The compositions of Cu2O_gCN before and after illumination were compared to evaluate the photostability of samples. In addition to the majority of Cu2O crystals, other copper species, CuO or metallic Cu, were presented and considered as the assistance for CO2 adsorption or interfacial charge transfer. Improved conversion of CO2 to CO was achieved by combining n-type gCN and p-type Cu2O crystals with an optimum surface composition, and by selecting the Cu2O crystals with higher photostability.