Electronic, Magnetic, and Catalytic Properties of Thermodynamically Stable Two-Dimensional Transition-Metal Phosphides

Two-dimensional (2D) nanomaterials have attracted extensive interest due to their unique properties and versatile applications. In the current work, a new family of 2D nanostructures, 2D transition-metal phosphide monolayer (M2P), is designed to find its multifunctional applications on the basis of density functional theory (DFT) calculations. We show that the 2D M2P monolayers are thermodynamically stable by carrying out molecular dynamic simulations, analyzing their phonon dispersions, and calculating their mechanical properties. We find that all of the stable 2D M2P monolayers are metallic, and their magnetic states strongly depend on the transition metals and geometric phases. We further demonstrate that 2D W2P and Fe2P monolayers in the 2H phase show the best catalytic performance in hydrogen evolution reaction (HER) due to the relatively low overpotentials at high hydrogen coverage. Importantly, oxygen functionalization can efficiently improve the HER activities of the 2D M2P monolayers at low hydrogen coverage. Our systematic study predicts that these new thermodynamically stable 2D transition-metal phosphides could be applicable in nanodevices, spintronics, and electrocatalysis.