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 differ?ent locations. Scientists are struggling to enhance the effciencies 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 effcient for pro?duction 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 effciency 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.