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 degrees 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 x 10(20) 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.