Oxygen doping enhances piezo-photocatalytic degradation of carbamazepine by molybdenum disulfide

Environmental pollution from persistent pharmaceuticals like carbamazepine (CBZ) poses severe risks to aquatic ecosystems and human health, yet conventional treatments struggle with low concentrations and secondary pollution. Piezo-photocatalysis, which harnesses mechanical and solar energies to drive charge separation, offers a promising alternative using materials such as molybdenum disulfide (MoS₂), whose layered structure enables tunable piezoelectricity but is hindered by rapid electron-hole recombination and structural instability. However, the mechanistic role of oxygen doping in repairing sulfur vacancies and enhancing symmetry-breaking for improved performance remains underexplored. Here we show that hydrothermally synthesized oxygen-doped MoS₂ (O₅-MoS₂) fully degrades 2 mg L^-1 CBZ in 25 min under combined ultrasound and visible light, achieving a rate constant (k _obs) of 0.13 min^-1-11.4 times higher than undoped MoS₂. This stems from oxygen substitution narrowing the bandgap to 1.94 eV, boosting the piezoelectric coefficient to 63 p.m. V^-1 (versus 26 p.m. V^-1), and generating a 0.19 V built-in potential that drives charge separation, as confirmed by 4.18 μA cm^-2 synergistic photocurrents, density functional theory calculations revealing heightened Mo-O charge transfer (2.08-2.36 e^-), and finite element simulations of deformation-induced fields. Over five cycles, O₅-MoS₂ retains 100 % efficiency with minimal Mo leaching (1.9 %), reducing product toxicity across fish, daphnid, and algal models. These findings delineate oxygen doping's dual role in defect mitigation and polarization enhancement, paving the way for robust piezo-photocatalytic systems in real-world water purification.