Boosting the photon absorption, exciton dissociation, and photocatalytic hydrogen- and oxygen-evolution reactions by built-in electric fields in Janus platinum dichalcogenides

Abstract

To achieve efficient photocatalysis for producing hydrogen and oxygen from dissociated water molecules using solar energy, all steps in the process – the photon absorption, exciton dissociation, carrier transfer and redox reactions – must be optimized because the overall efficiency is a product of all these fundamental efficiencies. However, most photocatalysts that have been investigated fulfil some but not all of these requirements, resulting in bottle necks in the process and a low overall solar-to-hydrogen efficiency. Here, we carry out a comprehensive investigation of the photocatalytic water-splitting performance of monolayer Janus platinum dichalcogenide materials, i.e., PtSSe, PtSTe and PtSeTe, using first-principles and GW calculations. It is found that the narrow-band gap PtSTe and PtSeTe materials exhibit excellent solar light absorption, covering a wide range of the solar spectrum, down to the near-infrared region. The unique feature of a strong internal vertical electric field in the Janus platinum dichalcogenides polarizes the electrons and holes in opposite chalcogen layers, leading to a reduced electron–hole recombination rate. These, combined with the large difference in the electron and hole mobilities, allow efficient carrier generation and transfer. The overpotential of PtSTe is 0.75 and 0.22 eV for the oxygen-evolution reaction and the hydrogen-evolution reaction, respectively, and its solar-to-hydrogen efficiency can reach up to 24.7%, breaking the conventional theoretical limit. Overall, our computations not only predict the promising photocatalytic application potential for water splitting of Janus platinum dichalcogenides but also suggest a valuable strategy for optimizing and improving the photocatalytic performance by utilizing the intrinsic polarizations of 2D polar materials.