On grounds of first principles calculations we propose two-dimensional semiconductors, ultrathin mono-, bi- and trilayers of PdPX (X=S, Se), as photocatalysts with band gaps suitable for harvesting the visible part of the solar spectrum and band edge energies matching the electrochemical potentials required for water splitting reaction. Layered bulk palladium phosphochalcogenides, among them the title compounds, have been known since 1971. The cleavage energy of ≈0.6 J m−2 suggests that single and few layer PdPX can be produced by exfoliation from the bulk phase. PdPX monolayer possesses a moderate band gap of 2.12 (1.97) eV for PdPS (PdPSe) and shows high, albeit anisotropic, carrier motilities. Bandgap (and edge) engineering is possible by applying strain (in the range of 1.5∼2.3 eV), and by varying the number of layers, that is, to 1.95(1.80) eV for the bi- and 1.75 (1.62) eV for the trilayer, to 1.70 (1.43) eV in the bulk.
Bibliographical noteFunding Information:
Financial support by the National Natural Science Foundation of China (No. 21403115 and 21522305), the NSF of Jiangsu Province of China (No. BK20150045), FlagERA (DFG HE 3543/ 27-1) and by the H2020 Marie Skłodowska–Curie Actions (H2020-MSCA-IF-2016, No.751848) is gratefully acknowledged. We thank ZIH Dresden for a computer time grant, and we thank Prof. Bruce Parkinson for an inspiring discussion.
All Science Journal Classification (ASJC) codes
- Organic Chemistry