Hexagonal assembly of Co3V2O8 nanoparticles acting as an efficient catalyst for visible light-driven water oxidation

Abstract

Co₃V₂O₈, a uniform hexagonal sheet-shaped morphology, for the first time acted as a robust catalyst for water oxidation. Under optimal photocatalytic conditions (photoirradiation at λ ≥ 420 nm, Ru(bpy)₃Cl₂ as the photosensitizer, Na₂S₂O₈ as the oxidant in borate buffer at pH = 8.5), the optimum apparent TOF of 10.9 μmol s⁻¹ m⁻² and O₂ initial evolution rate of 31.7 μmol s⁻¹ g⁻¹ were achieved, which, to our best knowledge, are the highest values reported for heterogeneous photocatalytic water oxidation to date. Variables of the photocatalytic reaction, including catalyst concentrations, pH, dye concentrations and oxidant concentrations, were systemically studied. The oxygen atoms of the evolved oxygen came from water, as confirmed by isotope-labeled experiments. The stability of Co₃V₂O₈ was tested and confirmed with multiple experiments (FT-IR, XRD, XPS), which indicated that Co₃V₂O₈ is a stable catalyst under water oxidation. In addition, a mechanism of Co₃V₂O₈ for the process of water oxidation was proposed.