Pd4S3Se3, Pd4S3Te3, and Pd4Se3Te3: Candidate Two-Dimensional Janus Materials for Photocatalytic Water Splitting

Abstract

The anisotropic Janus materials Pd4S3Se3, Pd4S3Te3, and Pd4Se3Te3 are demonstrated to be stable based on the cohesive energy, the phonon spectrum, and ab initio molecular dynamics simulation. They are semiconductors with indirect band gaps of 1.25, 0.78, and 1.32 eV, respectively, and exhibit ultrahigh carrier mobilities of up to 9455 cm2 V-1 s-1. Band edges enclosing the redox potentials of water enable photocatalytic water splitting. Importantly, the large intrinsic electric fields of the Janus structures facilitate the migration of photo-generated carriers, which enhances the carrier utilization and, therefore, the solar-to-hydrogen efficiency. The obtained efficiencies of 30.1% for Pd4S3Se3, 38.6% for Pd4S3Te3, and 23.8% for Pd4Se3Te3 surpass the conventional theoretical limit of 18%. In addition, the materials are predicted to catalyze the hydrogen and oxygen evolution reactions. Application potential is identified in electronics, optoelectronics, and photocatalytic water splitting.