Engineered MoS2 nanostructures for improved photocatalytic applications in water treatment

Two-dimensional (2D) Molybdenum disulfide (MoS2) has emerged as a fascinating new class of photocatalytic materials due to its flexible optoelectronic and physicochemical characteristics. However, the pristine MoS2 nanostructure still has limited application in water treatment due to the high recombination rate of charge carriers leading to reduced photocatalytic performance. Off late, there has been an upsurge of research on improving its photocatalytic action for environmental remediation. Consequently, research findings and the progress made have been consolidated in the form of review articles. Majority of these reviews summarized the catalytic role of MoS2 in hydrogen/oxygen evolution reactions (HER/OER), whereas none of them covers the strategies employed or could possibly be explored for improving photocatalytic activity and applications in water treatment. This review critically summarizes the merits, demerits and importance of different strategies adopted for improving photocatalytic performance of MoS2 such as scaling down to atomically thin (few/mono) nanosheets, construction of heterojunctions using other functional materials and defect engineering to achieve desired photocatalytic action. Further, the review discusses the actual asserted charge transfer of different heterojunctions that often misinterpreted and offers a mythical explanation restricted to the apparent redox-power of the targeted heterojunction. Generation of reactive species and its role in improved photocatalysis are also highlighted. Recent progress in MoS2-based photocatalytic systems for environmental remediation, including pollutant degradation and disinfection is also discussed. Finally, the future research directions for designing the superior next-generation MoS2-based photocatalysts are discussed.