PdSe 2 : Flexible Two-Dimensional Transition Metal Dichalcogenides Monolayer for Water Splitting Photocatalyst with Extremely Low Recombination Rate

With the growing demands of renewable energies and environmental protection, photocatalysts attract a lot of attention and are believed to be the most promising approach to harvest solar energy. Therefore, searching for suitable photocatalysts with wide-ranging solar absorption and efficient carrier separation becomes one of the most important tasks. Recently, a pentagonal 2D layered noble transition metal dichalcogenide PdSe 2 was exfoliated from bulk crystals with high stability and novel properties. In this work, we investigate the electronic and optical properties of monolayer PdSe 2 via density functional theory (DFT). Results show that the PdSe 2 monolayer exhibits anisotropic in-plane optical, electronic, and mechanical properties due to the low degree of lattice symmetry. In addition, suitable band gap and band edge positions are obtained, leading to a high solar-to-hydrogen (STH) efficiency up to 12.59%. By using nonadiabatic molecular dynamics (NA-MD) combined with the time-dependent DFT (TD-DFT), we estimate the time scale of electron–hole recombination time. Surprisingly, compared with normal monolayer materials, monolayer PdSe 2 exhibits an extremely slow electron–hole recombination process, with the time scale on the order of 1.9 ns. Our findings conclude that monolayer PdSe 2 is a promising candidate for further water-splitting applications.