Probing Active Sites on Pristine and Defective MnPX₃ (X: S and Se) Monolayers for Electrocatalytic Water Splitting

The state-of-the-art density functional theory approach was used to study the structural and electronic properties of pristine and defective MnPX₃ monolayers as well as their activity toward water and hydrogen evolution reaction (HER) catalytic performance. The adsorption behavior of H₂O on a pristine MnPX₃ structure is of physisorption nature, whereas the adsorption energy is significantly increased for the defective structures. At the same time, the water dissociation process is more energetically favorable, and the reactivity of MnPX₃ is determined by the vacancy configuration. Following Nørskov's approach, the HER catalytic performance is evaluated by calculating the hydrogen adsorption free energy on the respective MnPX₃ surface. Our calculation results demonstrate that defective 2D MnPX₃ with low coordinated P shows significantly higher HER performance compared to the pristine counterpart.