Hierarchical Cu2O photocathodes with nano/microspheres for solar hydrogen generation

Abstract

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.