Photocatalysis is a great technology to treat wastewater with environmental protection, more straightforward operation, high mineralization rate, and strong oxidation ability to efficiently remove the low concentration of organic pollutants in water.Tungsten trioxide (WO3) is a promising candidate for photocatalyst owing to its narrow energy gap (2.4–2.8 eV), high oxidation potential (+3.1–3.2 VNHE) of the valence band (VB), which is further meritorious for inducing the performance under visible light. WO3 is a widely studied metal oxide semiconductor for many cutting-edge applications such as photo/electrocatalysis, energy storage, smart window, antibacterial, anticancer agents, and pathogens control. Zinc tungstate (ZnWO4) has a wide band gap (about 3.8–5.7 eV) and possesses matched band structures with WO3. The introduction of ZnWO4 not only significantly promotes electron-hole separation but also broadens the absorption edge of WO3 and increases light absorption. Moreover, the addition of noble metal silver (Ag) can improve visible-light photocatalytic efficiency due to the increase of electron-transfer between semiconductor and noble metal.

Photocatalytic degradation has emerged as a promising technology for complete wastewater decontamination because of its organic and synthetic dormancy, essential limit, cost-viability, and long-haul security against chemical corrosion.

Global energy demand, mainly based on unsustainable fossil fuels, has grown considerably during the last decades. Moreover, the emission of green house gases had caused environmental pollution and global warming.

Metal oxide semiconductor (MOS) materials have been widely applied for gas sensing and environmental protection, because of their wide availability and high sensitivity to low ppm concentration of gases.