Hierarchical Cu2O photocathodes with nano/microspheres for solar hydrogen generation†
A hierarchical p-type Cu2O film with nano/microspheres on copper foil is successfully synthesized via a facile and cost-effective liquid reduction route through transformation of a lotus-like CuO/Cu(OH)2 nanosheet/nanowire structure. Various sizes of sphere-like Cu2O are transformed from CuO nanosheets and Cu(OH)2 nanowires by chemically reducing the oxides from Cu2+ to Cu1+ in a solution of ascorbic acid at a low temperature of 60 °C. Mott–Schottky analysis shows the flat band potential of the sphere-like Cu2O film to be −0.11 V and an acceptor concentration of 2.7 × 1020 cm−3. A direct band gap of 2.02 eV in Cu2O film is determined by incident photon-to-electron conversion efficiency measurements. Significantly, this hierarchical Cu2O photocathode exhibits remarkable photoelectrochemical activity in visible light. These results demonstrate that the Cu2O film with nano/microspheres has great potential in solar hydrogen applications.