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

A novel metal-free all-solid-state z-scheme g-C₃N₄/NCDs/WO_x 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/WO_x binary heterojunctions. The apparent quantum efficiency is 7.58% at 420 nm. The localized surface plasmon resonance effect of WO_x and the up-converted photoluminescence property of NCDs enhanced the utilization efficiency of NIR light together. In addition, the matched energy band structures of WO_x 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/WO_x 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.