Properties, optimized morphologies, and advanced strategies for photocatalytic applications of WO3 based photocatalysts.

The development of WO3 based photocatalysts has gained considerable attention across the world, especially in the realm of environmental remediation and energy production. WO3 has a band gap of 2.5- 2.7 eV that falls under the visible region and is thus a potential candidate to utilize in various photocatalytic processes. As an earth-abundant metal oxide, WO3 discovered in 1976 displayed excellent electronic and morphological properties, good stability, and enhanced photoactivity with diverse crystal phases. Also, it unveils non-toxicity, high stability in drastic conditions, biocompatibility, low cost, excellent hole mobility (10 cm2 V-1s-1), and tunable band gap. This review provides a comprehensive overview of the different properties of WO3 inclusive of crystallographic, electrical, optical, thermoelectrical, and ferroelectric properties. The different morphologies of WO3 based on dimensions were obtained by adopting different fabrication methods including inspecting their effects on the efficiency of WO3. Numerous strategies to construct an ideal photocatalyst such as engineering crystal facets, surface defects, doping, heterojunction formation explaining specifically type-II, Z-scheme, and S-scheme mechanisms with addition to carbonaceous based WO3 nanocomposites are summed up to explore the photocatalytic performance. The typical application of WO3 is deliberated in detail involving the role and efficiency of WO3 in pollutant degradation, CO2 photoreduction, and water splitting. Besides, other applications of WO3 as gas-sensor, bio-sensor, decomposition of VOCs, heavy metals ions adsorption, and antimicrobial property are also included. Moreover, the numerous aspects responsible for the high efficiency of WO3-based nanocomposites with their challenges, opportunities, and future aspects are summarized. Hopefully, this review may inspire researchers to explore new ideas to boost the production of clean energy for the next generation.