Corrosion of catalyst in high resolution: Layered transition metal dichalcogenides electrocatalyse water splitting and corrode during the process

Among the vast field of 2D materials, transition metal dichalcogenides (TMDs) have emerged as promising materials for electrocatalysis. Many of them, such as MoS₂, were found to be potent electrocatalysts for the hydrogen evolution reaction (HER), which is vital for making electrochemical water splitting, a green route for obtaining hydrogen, economically feasible. In this work, we investigated the morphological and (electro)chemical changes undergoing in synthetic bulk crystals of MoS₂, TiS₂, and TiSe₂ during HER. Local electrochemical changes were observed using scanning electrochemical microscopy (SECM). Scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM) were utilized to monitor morphological changes. Furthermore, the chemical composition of the materials was analyzed using X-ray photoelectron spectroscopy (XPS) and electron dispersive X-ray spectroscopy (EDS). Changes in the atomic structure were studied using X-ray diffraction (XRD). Our experiments showed different degrees of corrosion occurring in these materials, with the magnitude of corrosion decreasing in the order TiSe₂ > TiS₂ > MoS₂. These findings are of tremendous importance for the development of transition metal dichalcogenide electrocatalysts, which are touted to replace platinum for hydrogen evolution reaction.