Janus Mo₂P₃ Monolayer as an Electrocatalyst for Hydrogen Evolution

The rational design of low-cost electrocatalysts with the desired performance is the core of the large-scale hydrogen production from water. Two-dimensional materials with high specific surface area and excellent electron properties are ideal candidates for electrocatalytic water splitting. Herein, we identify a hitherto unknown Mo2P3 monolayer with a Janus structure (i.e., out-of-plane asymmetry) through first-principle structure search calculations. Its inherent metallicity ensures good electrical conductivity. Notably, its catalytic activity is comparable to that of Pt and the density of active sites is up to 2.65 × 1015 site/cm2 owing to the Mo → P charge transfer enhancing the catalytic activity of P atoms and asymmetric structure exposing more active sites to the surface. The Mo2P3 monolayer can spontaneously produce hydrogen through the Volmer–Heyrovsky pathway. These excellent performances can be well maintained under strain. The coexistence of covalent and ionic bonds results in Mo2P3 having high stability. All these excellent properties make the Mo2P3 monolayer a promising candidate for electrocatalytic water splitting.