Modification strategies of metal oxide photocatalysts for clean energy and environmental applications: A review

In the modern world, the industrial revolution to meet consumer demand increases the need for clean energy production and a sustainable environment. Photocatalysis is envisioned among the promising strategies to fulfill the preceding global demands in an eco-friendly way. Among photocatalysts, metal oxides (MOs) are considered promising candidates owing to their efficiency, low cost, and environment-friendliness. In addition, sufficient availability, ease of fabricating method, and high surface area make MOs suitable for extensive use in a vast domain. However, certain limitations such as wide band-gap, the high recombination rate of photo-generated electron-hole pairs, and catalyst deactivation hamper their practical applications. In this review, various strategies mainly employed to address the challenging issues associated with MOs are comprehensively highlighted. Likewise, the preparation mechanism of MOs with different morphologies, types of photocatalysis and its reaction pathways, detailed analysis of stability and the structure-property relationship, and challenges about the issue of durability and reusability of MO photocatalysts are discussed in detail. In addition, the use of MOs as an effective photocatalyst for CO2 reduction, hydrogen generation, and pollutant degradation is also discussed in detail.