Understanding the advantage of hexagonal WO 3 as an efficient photoanode for solar water splitting: a first-principles perspective

• Published in: Journal of materials chemistry. A, Materials for energy and sustainability Vol. 4; no. 29; pp. 11498 - 11506
• Main Authors: Lee, Taehun, Lee, Yonghyuk, Jang, Woosun, Soon, Aloysius
• Format: Journal Article
• Language: English
• Published: 2016
• ISSN: 2050-7488; 2050-7496
• DOI: 10.1039/C6TA03659G

Polycrystalline WO 3 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 WO 3 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-WO 3 (and its surfaces) over the larger band gap γ-WO 3 phase for the anode in water splitting. Notably, after addressing the relative thermodynamic stability of the various h-WO 3 surfaces, we carefully quantify and compare the electronic band structure of these two bulk phases of WO 3 (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-WO 3 match up with the redox potential of water and other possible cathode materials.