Enhanced photoreduction of CO₂ into methanol by facet-dependent Cu₂O/reduce graphene oxide

The preparation of cuprous oxide (Cu₂O) with different morphologies and oxidation states decorating with reduced graphene oxide (rGO) and their comparison in the photocatalytic reduction of CO₂ are reported in the present work. The rhombic dodecahedra Cu₂O/rGO exhibits the highest methanol yield (355.3 μmol g^-1cat) which is ca. 4.1-80.8 times superior to cubic, octahedral Cu₂O/rGO and CuO/rGO after 20 h of visible light illumination. The enhanced performance may be due to the unique rhombic dodecahedra structure with less band bending of conduction and valence bands which decrease the energy barrier for the transfer of photogenerated electrons to the surface. The incorporation of rGO should assist the transfer of photogenerated electrons from conduction band of Cu₂O. The positively charged dodecahedra Cu₂O/rGO may also increase the adsorption of carbonate anions from dissolution of CO₂ gas. This work provides a facile solution-chemistry route to synthesize rGO incorporated crystal Cu₂O with various facets as visible-light-active photocatalysts for CO₂ utilization by using natural sunlight.