Z-scheme design of Ag@g-C3N4/ZnS photoanode device for efficient solar water oxidation: An organic-inorganic electronic interface

Abstract

Abstract Herein, we demonstrate a design of a composite photoanode comprising a very thin layer of ZnS NPs onto a dense layer of Ag@g-C3N4 to form a dual absorber tandem device based on organic-inorganic electronic interface for photo water-splitting. The XRD pattern of Ag@g-C3N4 showed both the diffraction peaks of cubic Ag and main peak of g-C3N3. The XPS survey spectrum confirms the existence of the C, N, Ag, Zn, and S elements on the surface of the Ag@g-C3N4/ZnS photoelectrode. With incorporating Ag in g-C3N4 structure, the band gap decreased from 2.90 for g-C3N4 to 2.55 eV for Ag@g-C3N4 and also light absorption ability increased. The device based on the architecture of TiO2/Ag@g-C3N4/ZnS/Ni(OH)2 showed a photocurrent of about 0.1 and 0.2 mA cm−2 at potential of 1.23 and 1.7 V vs. RHE. The Ag@g-C3N4/ZnS photoanode exhibited a photocurrent turn-on potential of 0.45 V vs. RHE. In this photoanode device, Ag@g-C3N4 as a second absorber layer could absorb the photons of visible light which are transparent to ZnS layer and transforms into additional photovoltage. This architecture introduces a successful band alignment for high efficiency water-splitting through organic-inorganic junction.