Triple-Channel Charge Transfer over W18O49/Au/g-C3N4 Z-Scheme Photocatalysts for Achieving Broad-Spectrum Solar Hydrogen Production

Abstract

Z-scheme heterojunctions are fundamentally promising yet practically appealing for photocatalytic hydrogen (H-2) production owing to the enhanced redox power, spatial separation of charge carriers, and broad-spectrum solar light harvesting. The charge-transfer dynamics at Z-scheme heterojunctions can be accelerated by inserting charge- transfer mediators at the heterojunction interfaces. In this study, we introduce Au nanoparticle mediators in the Z-scheme W18O49/g-C3N4 heterostructure, which enables an improved H-2 production rate of 3465 mu mol/g.h compared with the direct Z-scheme W18O49/g-C3N4 (1785 mu mol/g.h) under 1 sun irradiation. The apparent quantum yields of H-2 production with W18O49/Au/g-C3N4 are 3.9% and 9.3% at 420 and 1200 nm, respectively. The improved photocatalytic H-2 production activity of W18O49/Au/g-C3N4 is attributable to the triple-channel charge-transfer mechanism: channel I.Z-scheme charge transfer facilitates charge separation and increased redox power of the photoexcited electrons; channels II and III.the localized surface plasmon resonances from Au (channel II) and W18O49 (channel III) enable light harvesting extension from visible to near-infrared wavelengths.