Visible-light-driven nonsacrificial hydrogen evolution by modified carbon nitride photocatalysts

Abstract

Pt-loaded graphitic carbon nitride (g-C3N4) is known to be a good photocatalyst for H2 evolution under visible light. In most cases, however, sacrificial electron donors such as triethanolamine are required for the water-splitting operation, and nonsacrificial H2 evolution by g-C3N4 remains a challenge. In this work, we investigated the photocatalytic activities of carbon nitride nanosheet (NS-C3N4), which was prepared by thermal treatment of urea, for nonsacrificial H2 evolution using reversible electron donors under visible light (λ > 400 nm). Whereas Pt-loaded NS-C3N4 did not produce H2 from aqueous solutions containing I−, Fe2+, or [Fe(CN)6]4–, modification of the Pt/NS-C3N4 photocatalyst with CrOx led to observable H2 evolution. Transmission electron microscopy observations and energy-dispersive X-ray spectroscopic analysis suggested that a Pt-core/CrOx-shell structure was formed on the NS-C3N4. The CrOx/Pt/NS-C3N4 served as a H2-evolution photocatalyst for visible-light-driven Z-scheme overall water splitting, in combination with a modified WO3 photocatalyst, in the presence of a [Fe(CN)6]3–/4– redox mediator.