Design of novel photocatalysts from first principles

Dr Judy Hart talks about the design of novel photocatalysts from first principles - Solid solutions with tunable bandgaps.

Abstract

Smart Many potential semiconductors for photocatalysis of water splitting, including TiO2, have band gaps that are too large for absorption of visible light and hence have low efficiencies under sunlight. Solid solution formation is one approach to reducing band gaps and enhancing visible-light absorption.

For example, it has been shown that GaN-ZnO solid solutions are promising visible-light photocatalysts

[1]. In this work, we use density functional theory calculations to investigate the electronic properties of ZnO-AlN and ZnS-GaP solid solutions and their potential as photocatalysts. The solid solutions are found to have small energies of mixing from the two constituents, and tunable band gaps that depend on both composition and atomic ordering. Significantly, the band gaps of the solid solutions are often smaller than those of either constituent on their own. Addition of only a small amount of AlN to ZnO and GaP to ZnS reduces the band gap into the correct energy range for absorption and emission of visible light and close to the optimum for photocatalysis of water splitting under sunlight [2]. Furthermore, addition of a small amount of ZnS to GaP produces a direct band gap semiconductor, in contrast to pure GaP which has an indirect band gap, and this should therefore increase the efficiency of light absorption. Preliminary experimental results show high photocatalytic actvitiy for ZnS-GaP thin films under visible light, in agreement with the computational predictions.

[1] K. Maeda, et al., Nature, 440 (2006) 295.

[2] J. N. Hart, N. L. Allan, Advanced Materials, 25 (2013) 2989.

Biography

Dr Judy Hart joined the School of Materials Science and Engineering at UNSW as a Lecturer in July, 2013. She was previously a Ramsay Memorial Fellow and lecturer in the Centre for Computational Chemistry, University of Bristol, U.K. Her research interests are in the combined use of computational and experimental approaches to design new semiconductor materials, particularly for applications in photocatalysis.