Bifunctional Nitrogen-Doped Carbon Dots in g-C3N4/WOx Heterojunction for Enhanced Photocatalytic Water-Splitting Performance.

A novel metal-free all-solid-state z-scheme g-C3N4/NCDs/WOx photocatalyst was fabricated using nitrogen-doped carbon dots (NCDs) as the electron mediator. As-prepared sandwich-structured composites displayed enhanced visible and NIR light photocatalytic activity. Under visible light irradiation, the hydrogen evolution rate reached 3.27 mmol g-1 h-1, which increased to roughly seven times higher than that of pure g-C3N4 and roughly twice that of g-C3N4/NCDs or g-C3N4/WOx binary heterojunctions. The apparent quantum efficiency is 7.58% at 420 nm. The localized surface plasmon resonance effect of WOx and the up-converted photoluminescence property of NCDs enhanced the utilization efficiency of NIR light together. In addition, the matched energy band structures of WOx and g-C3N4 as well as the effective electron conductor (NCDs) between them accelerate electron transfer at the interface. The all-solid-state z-scheme g-C3N4/NCDs/WOx photocatlyst was confirmed by a series of characterizations and experiment results. This report offered new insights into constructing an efficient all-solid-state z-scheme photocatalyst to be applied during the photocatalytic water-splitting reaction in the visible and NIR light regions.