PdSe₂: 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 PdSe2 was exfoliated from bulk crystals with high stability and novel properties. In this work, we investigate the electronic and optical properties of monolayer PdSe2 via density functional theory (DFT). Results show that the PdSe2 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 PdSe2 exhibits an extremely slow electron–hole recombination process, with the time scale on the order of 1.9 ns. Our findings conclude that monolayer PdSe2 is a promising candidate for further water-splitting applications.