Z-Scheme in a Co3(PO4)2/α-Fe2O3 photocatalysis system for overall water splitting under visible light

Abstract

Overall water splitting under solar irradiation with a semiconductor has long been investigated as an attractive pathway to convert solar energy into chemical energy in the form of H₂. However, using only a single semiconductor as a photocatalyst remains a great challenge. Designing Z-scheme systems is the most common method used for photocatalysis. We report a Z-scheme Co₃(PO₄)₂/α-Fe₂O₃ structure as an efficient photocatalyst for overall water splitting under visible light. The as-prepared Co₃(PO₄)₂/α-Fe₂O₃ photocatalyst shows excellent improvement in visible light absorption and photocatalytic efficiency for overall water splitting, in which Co₃(PO₄)₂ and Fe₂O₃ act as H₂-evolving and O₂-evolving photocatalysts, respectively. By varying the amount of α-Fe₂O₃ in the photocatalysts, we found that Co₃(PO₄)₂/α-Fe₂O₃-1.6% exhibited the optimal photocatalytic activity in hydrogen production (0.63 μmol h⁻¹) and oxygen evolution (0.32 μmol h⁻¹), which is almost 35-fold higher than that of a pure Co₃(PO₄)₂ catalyst. In addition, the chemical stoichiometric ratio of H₂ and O₂ in the photocatalysis process is almost 2 : 1. The enhanced photocatalytic activity was attributed to the synergetic effects of Co₃(PO₄)₂ and α-Fe₂O₃ in the Z-scheme structure, which resulted in highly efficient separation of photogenerated charge carriers.