Recent developments in ZnO-based heterostructures as photoelectrocatalysts for wastewater treatment: A review

The industry's global expansion has resulted in a significant increase in the production and accumulation of harmful pollutants in the environment. Many researchers were interested in employing ZnO semiconductor material as a photocatalyst due to its environmentally friendly nature, biocompatible, availability and durability qualities for eliminating harmful pollutants. This review critically examines the findings and highlights new research based on ZnO heterostructures as a photoelectrocatalyst (PEC) for the remediation of organically polluted wastewater. It also discusses significant advancements to overcome the challenges associated with bare ZnO. Numerous efforts have taken on the hybridization of ZnO along with a narrow bandgap material, metal/non-metal doping and the construction of heterojunction that extends the absorption region of ZnO from UV to the visible region and reduces the photo-corrosion process up to a certain extent. Furthermore, the load separation/transfer mechanism, enhancement of photocatalytic activity strategies and improved light-harvesting capabilities of ZnO have been elaborated in detail. This review contains intriguing information for future research and highlights the use of ZnO-based heterostructures, which can be used as photoelectrocatalysts for wastewater purification. In the near future, attention must be paid to developing a low-cost photocatalyst immobilization technology for solid-liquid separation and catalyst reuse. In order to assure environmental safety and cost-effectiveness, the use of abundant and non-toxic components is desirable. Furthermore, due to the vast availability of solar energy, future research works must focus on employing natural sunlight as an illumination source, compared to commercially simulated solar light. Finally, this paper elaborates on potential enhancements and intriguing future directions for the use of modified ZnO as a photoelectrocatalysts.