Theoretical Insights of the Photocatalytic and Hydrogen Storage Ability of Two-Dimensional (2-D) MoSe (MX) and MoSSe (MXY) ( = Se, = S) ML Using DFT Study

Two-dimensional (2-D) material-based photocatalysts are promising candidates for generating hydrogen like clean fuel to contribute toward a sustainable environment. In this study, the electronic (optical) properties of MoSe2 (MX2) and MoSSe (MXY) ML with their various applications (as water splitting, hydrogen storage, and photo-detectors) are studied systematically using first-principles calculations. At first, the total density of states (TDOSs), band structure, and work function (WF) are reported as electronic properties, indicating the semiconducting (2H) nature of both MoSe2 and MoSSe ML. Second, the optical properties of MoSe2 and MoSSe ML are plotted and analyzed relative to each other. The enhanced absorption spectrum ( $\alpha $ ) is marked by the peaks of MoSSe ML aligning in the visible region (VR) with an increased value of 7.07% compared to the MoSe2 ML. The photocatalytic potential of MoSSe ML for initiating the process of water splitting highlights the novelty of the work. As a result, the thermodynamic stability is given by a Gibbs free energy ( $\Delta G$ ) of 0.098 eV, which is close to 0 eV. Thus, the separation of photogenerated charge carriers is facilitated by a small binding energy of −0.66 eV. Later, the hydrogen storage of pristine MoSSe ML is presented as another application. Also, gravimetric density ( ${G}_{\text {theoretical}}$ ) and desorption below room temperature ( ${T}_{\text {des}}$ ) promote easy storage of hydrogen. Consequently, with higher absorption ability, pristine MoSSe (MXY) ML as a self-powered photodetector is studied. Lastly, the research concludes that MoSSe ML is a promising material for designing of nanoelectronic devices.