Position-selected cocatalyst modification on a Z-scheme Cd0.5Zn0.5S/NiTiO3 photocatalyst for boosted H2 evolution

Abstract

Photocatalytic water splitting by semiconductors is a promising technology to produce clean H₂ fuel, but the efficiency is restrained seriously by the high overpotential of the H₂-evolution reaction together with the high recombination rate of photoinduced charges. To enhance H₂ production, it is highly desirable yet challenging to explore an efficient reductive cocatalyst and place it precisely on the right sites of the photocatalyst surface to work the proton reduction reaction exclusively. Herein, the metalloid Ni_xP cocatalyst is exactly positioned on the Z-scheme Cd_0.5Zn_0.5S/NiTiO₃ (CZS/NTO) heterostructure through a facile photodeposition strategy, which renders the cocatalyst form solely at the electron-collecting locations. It is revealed that the directional transfer of photoexcited electrons from Cd_0.5Zn_0.5S to Ni_xP suppresses the quenching of charge carriers. Under visible light, the CZS/NTO hybrid loaded with the Ni_xP cocatalyst exhibits an optimal H₂ yield rate of 1103 μmol h⁻¹ (i.e., 27.57 mmol h⁻¹ g⁻¹), which is about twofold of pristine CZS/NTO and comparable to the counterpart deposited with the Pt cocatalyst. Besides, the high apparent quantum yield (AQY) of 56% is reached at 400 nm. Further, the mechanisms of the cocatalyst formation and the H₂ generation reaction are discussed in detail.