ZrO₂-based heterojunction engineering for enhanced visible-light photocatalysis: a review

Rapid industrialization has significantly increased water pollution worldwide, requiring sustainable and efficient technology for water treatment. Visible-light-assisted photocatalysis is one of the promising techniques that can be employed for environmental remediation by oxidizing various pollutants through the use of solar energy. Zirconium dioxide (ZrO₂) is an environmentally friendly and chemically stable compound with high oxidative power, but it suffers from a wide bandgap that inhibits the utilization of visible light. The fundamental principles of photocatalysis, intrinsic properties and limitations of bare ZrO₂, heterojunction formation approaches, synthesis methods, characterization analysis, and photocatalytic mechanism have all been discussed in this critical review of current progress in ZrO₂-based heterojunction photocatalysts for water purification. Issues related to stability and recyclability of catalysts, charge carrier behaviour, photocatalytic activity, and the influence of test conditions have been critically analysed. This review highlights the importance of standardization of photocatalytic experiments, testing of stability, evaluation under realistic wastewater systems, and complete investigation of mineralization and energy efficiency. In order to rationalise the development of robust, efficient, and practical ZrO₂-based heterojunction photocatalysts for sustainable water purification, current knowledge gaps and future perspectives have been highlighted.