Experimental and DFT Studies of Au Deposition Over WO₃/g-C₃N₄ Z-Scheme Heterojunction

A typical Z-scheme system is composed of two photocatalysts which generate two sets of charge carriers and split water into H₂ and O₂ at different locations. Scientists are struggling to enhance the efficiencies of these systems by maximizing their light absorption, engineering more stable redox couples, and discovering new O₂ and H₂ evolutions co-catalysts. In this work, Au decorated WO₃/g-C₃N₄ Z-scheme nanocomposites are fabricated via wet-chemical and photo-deposition methods. The nanocomposites are utilized in photocatalysis for H₂ production and 2,4-dichlorophenol (2,4-DCP) degradation. It is investigated that the optimized 4Au/6% WO₃/CN nanocomposite is highly efficient for production of 69.9 and 307.3 µmol h^-1 g^-1 H₂ gas, respectively, under visible-light (λ > 420 nm) and UV-visible illumination. Further, the fabricated 4Au/6% WO₃/CN nanocomposite is significant (i.e., 100% degradation in 2 h) for 2,4-DCP degradation under visible light and highly stable in photocatalysis. A significant 4.17% quantum efficiency is recorded for H₂ production at wavelength 420 nm. This enhanced performance is attributed to the improved charge separation and the surface plasmon resonance effect of Au nanoparticles. Solid-state density functional theory simulations are performed to countercheck and validate our experimental data. Positive surface formation energy, high charge transfer, and strong non-bonding interaction via electrostatic forces confirm the stability of 4Au/6% WO₃/CN interface.