Vacancy controlled MoSSe/MnSe heterostructure show boosting activities in photoelectrochemical and electrocatalytic hydrogen production

There are many factors that affect the activity of catalyst, such as the absorption capacity of catalyst itself, carrier separation, active site and surface transfer efficiency. In the study of this paper, two main influencing factors of catalyst are considered. One is that the electronic band structure determines the carrier separation and transport efficiency; the other is surface chemical state affects the active sites. A vacancy controlled MoSSe/MnSe heterojunction catalyst was demonstrated: MoSSe formed a type II heterojunction with MnSe, allowing photo generated carriers to move between the conduction and valence bands of the two semiconductors, thereby improving separation efficiency. Under the optimized MnSe composite ratio, MSMS3 exhibited a photocurrent density of up to −7.153 mA/cm2 at 0 V vs RHE, which is 5.2 times that of the MoSSe. In addition, the catalyst was further treated with ethylene diamine tetraacetic acid (EDTA). Due to the weak binding between Mn and Se, a large number of Mn atoms detach and form many Mn vacancies (VMn) on the catalyst surface due to the complexation effect of EDTA. These vacancies provide a large number of active sites, reduce of the adsorption energy barrier for H* which greatly enhancing the activity of the catalyst in hydrogen evolution reactions. Compared with the original MoSSe (overpotential 476 mV, Tafel slope 216 mV/dec), the overpotential of the vacancy catalyst MSMS3v is reduced to 197 mV with a Tafel slope of 77 mV/dec. This work demonstrates a novel catalyst regulation strategy.