Mixing Thermodynamics and Photocatalytic Properties of GaP–ZnS solid solutions

• Published in: Advanced theory and simulations 2019-03, Vol.2 (3), p.n/a
• Main Authors: Shenoy, Joel, Hart, Judy N., Grau‐Crespo, Ricardo, Allan, Neil L., Cazorla, Claudio
• Format: Article
• Language: English
• Subjects: density functional theory calculations; multiconfigurational supercell approach; photocatalytic materials; semiconductor solid solutions
• ISSN: 2513-0390; 2513-0390
• DOI: 10.1002/adts.201800146

Preparation of solid solutions represents an effective means to improve the photocatalytic properties of semiconductor‐based materials. Nevertheless, the effects of site‐occupancy disorder on the functional properties of materials are difficult to predict and consequently many experimental trials may be required before achieving enhanced photocatalytic activity. Here, first‐principles methods are employed to estimate the mixing free energy and the structural and electronic properties of (GaP)x (ZnS)1−x solid solutions. The method relies on a multi‐configurational supercell approach that takes into account the configurational and vibrational contributions to the free energy. Phase competition among the zinc‐blende and wurtzite polymorphs is also considered. Overall excellent agreement with the available experimental data is demonstrated, namely: 1) zinc‐blende is energetically most favorable, 2) the solid solution energy band gap lies within the 2–3 eV range, and 3) the energy band gap of the solid solution is direct for compositions x≤75%. It is found that at ambient conditions, (GaP)x (ZnS)1−x solid solutions with x≈25%, 50% and 75% render promising hydrogen evolution photocatalysts for water splitting under visible light, owing to their favorable energy band gaps and band levels relative to vacuum. A multi‐configurational supercell approach based on first‐principles calculations is used to analyze the mixing thermodynamics and electronic properties of (GaP)x(ZnS)1−x solid solutions. Compositions close to 25%, 50%, and 75% are found to be promising photocatalysts for hydrogen production from water splitting due to their favorable energy band gaps and band levels relative to vacuum. .