Polycrystalline WO3 has been suggested as an alternative photoanode material for the water splitting reaction. However, the band gap and band edge positions of the most commonly used γ-monoclinic WO3 phase are found to be not optimal for effective water oxidation. In this work, by using first-principles density-functional theory calculations with an ab initio thermodynamic model, we demonstrate the potential advantage of using h-WO3 (and its surfaces) over the larger band gap γ-WO3 phase for the anode in water splitting. Notably, after addressing the relative thermodynamic stability of the various h-WO3 surfaces, we carefully quantify and compare the electronic band structure of these two bulk phases of WO3 (using their valence and conduction band edges as descriptors). We then provide a simple perspective as to illustrate how the surface band edges of h-WO3 match up with the redox potential of water and other possible cathode materials.
Bibliographical noteFunding Information:
We gratefully acknowledge support from the Basic Science Research Program by the NRF (grant no. 2014R1A1A1003415). Computational resources have been provided by the KISTI supercomputing center (KSC-2015-C3-030).
© 2016 The Royal Society of Chemistry.
All Science Journal Classification (ASJC) codes
- Renewable Energy, Sustainability and the Environment
- Materials Science(all)