Interface engineering and charge transfer mechanisms in MoS2-based heterojunctions for phenolic photocatalysis: A state-of-the-art review

Phenolic pharmaceuticals are priority water contaminants because of their toxicity, persistence, and recalcitrance to biodegradation. Photocatalytic advanced oxidation offers a sustainable route for their complete mineralization. Molybdenum disulfide (MoS 2 ) is a promising two-dimensional semiconductor with tunable band structure, abundant active sites, and visible-light absorption. However, pristine MoS 2 suffers from rapid charge recombination and limited surface reactivity. Constructing heterojunctions with suitable semiconductors enables spatial separation of photogenerated electrons and holes, thereby enhancing photocatalytic efficiency. This review systematically summarizes recent advances in MoS₂-based heterojunctions for phenolic pollutant degradation. We first present the crystal structure and dimensionality-dependent electronic properties of MoS 2 , then outline key synthesis methods, namely hydrothermal, CVD, exfoliation, electrodeposition, and ball milling, and their influence on morphology and performance. For heterojunction design, we clarify the charge-transfer mechanisms of type-II, Z -scheme, and S-scheme systems, highlighting their differences, connections, and emerging variants such as multi-component composites and piezo-photocatalytic synergy. Degradation performances toward phenol, chlorophenols, bisphenol A, and p-nitrophenol are critically reviewed with emphasis on operational parameters and mineralization pathways. A comprehensive characterization toolkit for mechanistic validation is presented, including radical trapping, band alignment analysis, charge separation assessment, in-situ spectroscopies, and DFT calculations. Finally, we identify persistent challenges: insufficient long-term stability, scale-up difficulties, performance loss in real wastewater, and inconsistent mechanistic interpretations, and propose future directions, including rational heterojunction engineering, defect-interface synergy, machine-learning-assisted screening, and integration with other oxidation processes. This review aims to guide the rational design of efficient MoS 2 -based photocatalysts and their practical application in phenolic wastewater treatment.