Enhancing electrochemical hydrogen evolution efficiency via UV ozone treatment: 3D electrode carbon cloths with defect-enriched MoS₂

Electrochemical water splitting, a key process for extracting hydrogen energy from water, is recognized as a promising eco-friendly technology. Molybdenum disulfide (MoS₂), especially when possessing abundant defects, emerges as a cost-effective and efficient catalyst for hydrogen evolution reaction (HER), presenting a viable alternative to noble metals such as platinum (Pt). However, the impact of UV-Ozone (UVO) in generating defects in bulk 2H-MoS₂ remains underexplored. Here, we successfully synthesized 2H-MoS₂ using the hydrothermal method on a 3D conductive carbon cloth. Subsequently, the sample underwent UVO treatment for three different durations of 10, 30, and 50 min. Our results demonstrate that a 50-minute exposure to UVO yields the most effective HER performance, with a significant decrease in the onset potential from 189 mV to 116 mV and a low Tafel slope of 64 mV/decade. This enhancement is attributed to increased surface activity, evident in a more than fourfold increase in double-layer capacitance (C_dl). Importantly, the 50-minute UVO treatment not only significantly improves the purity of MoS₂ and increases the number of edge sites, but also lead to an increase in sulfur vacancies and the formation of amorphous oxygen-incorporated MoS_x. These edge sites, along with sulfur vacancies and oxygens incorporation, are considered ideal for hydrogen binding, enhancing electron transport, and improving HER activity.