Carbamazepine, a common antiepileptic, is frequently detected in surface water, groundwater and drinking water, where it can induce toxic effects in aquatic organisms and potentially impact human health through long-term exposure. Conventional treatment technologies are often inefficient, have high energy demands or cause secondary pollution when addressing persistent compounds such as pharmaceutical contaminants. Current advanced oxidation processes (AOPs) are plagued by charge recombination, a phenomenon where the energy generated by light or motion is lost internally rather than being used to break down toxins, and single-energy dependence.
Credit: Environmental Science and Ecotechnology
By leveraging a dual-energy harvesting approach, researchers have developed a piezo-photocatalytic material that solves one of the most persistent challenges in water treatment: the rapid recombination of charge carriers. The study, published in Environmental Science and Ecotechnology, shows that oxygen-doped MoS2 can completely degrade carbamazepine within 25 minutes when ultrasound and visible light are applied simultaneously, outperforming conventional photocatalytic approaches.
Hydrothermal synthesis enables precise oxygen doping at sulfur vacancy sites
The research team used hydrothermal synthesis to perform precise defect engineering, substituting oxygen atoms into sulfur vacancy sites. The oxygen-doped version works because the oxygen atoms repair sulfur vacancies while breaking the material’s symmetry. By precisely controlling the oxygen substitutions, the team created an optimally doped material that exhibited exceptional performance, fully degrading 2 mg L-1 carbamazepine in just 25 minutes under combined ultrasound and visible-light irradiation. The observed reaction rate was more than 11 times higher than that of undoped MoS2, achieving a rate constant of 0.13 min-1.
This oxygen doping breaks the material’s crystalline symmetry, narrowing the bandgap to 1.94 eV, which allows the material to absorb a wider spectrum of visible light. The material also has a higher piezoelectric coefficient, 63 pm V-1, compared to 26 pm V-1. This generates an internal electric field of 0.19 V that acts as an internal separator, preventing electron-hole pairs from recombining and ensuring that the maximum number of reactive oxygen species are available for pollutant degradation.
High stability and low leaching pave the way for scalable water remediation
In stress tests, the catalyst maintained its integrity, with only 1.9% molybdenum leaching after five cycles, and it successfully reduced the toxicity of the water without introducing secondary pollution.
The findings provide a practical pathway for designing next-generation water purification technologies that operate efficiently under mild conditions using multiple renewable energy inputs. Piezo-photocatalytic systems based on defect-engineered materials could be integrated into decentralized or low-energy treatment facilities, particularly in regions lacking advanced infrastructure. Beyond carbamazepine, the catalyst also shows promise for degrading other antibiotics and organic pollutants, suggesting broad applicability. By linking material structure, electronic behavior and catalytic performance, this method offers valuable design principles for scalable, stable and environmentally friendly remediation technologies.
