WO3–based photocatalysts: A review on synthesis, performance enhancement and photocatalytic memory for environmental applications

A significant drawback of the traditional photocatalysts such as titanium dioxide (TiO2) is their inability to absorb visible light from the solar spectrum due to their wide band gap energy. They are only photoactive in the ultraviolet (UV) region which is just a little fraction of the solar spectrum and could be harmful with much exposure to it. Due to its abundance in the solar spectrum, visible light needs to be harnessed for environmental applications. However, we lack visible light driven photocatalysts with long-lasting energy storage capacity for “round-the-clock photocatalytic” (RTCP) applications. For this reason, there is a growing need to find new photocatalysts that can mitigate these bottlenecks. It is evident from some carefully selected published articles (1976–2021) that tungsten oxide (WO3) and its composites have attracted popularity in recent years because of its outstanding properties and particularly its smaller band gap energy of 2.8 eV. However, pristine WO3 is limited due to relatively low energy density and smaller specific surface area. These drawbacks can be addressed by developing various WO3 – based materials to improve their performance. This paper reviews and discusses their recent development in surface advancement, morphology control, modification of nanostructured WO3 and its composites, and their RTCP energy storage for photocatalytic activities in visible light and the dark for environmental applications. Specific aspects focused on its nature, structure, properties, synthesis, coatings, deposition, approaches at modifying and enhancing its visible light photoactivity for enhanced performance and energy storage potential.