Abstract
The conduction and valence band edges (EC and EV) of a material relative to the water redox potential levels are critical factors governing photocatalytic water splitting activity. Here we discuss the large discrepancy in the experimentally measured EC and EV of various transition metal oxides (TMOs) in vacuum and in an aqueous solution. We speculate that the discrepancy stems from the different degree of electron transfer across the surface due to the different environment at the surface of the TMOs in vacuum and water. Accurately modeling the electronic structure at TMO/water interfaces is a significant challenge, however. Using first-principles density functional theory calculations on rutile titanium dioxide and cobalt monoxide model systems, here we identify the optimal approaches to accurately predict the band edge positions in vacuum and water. We then validate the optimized schemes on other TMOs, demonstrating good agreement with experimental measurements in both vacuum and water.
Highlights
The conduction and valence band edges (EC and EV) of a material relative to the water redox potential levels are critical factors governing photocatalytic water splitting activity
The band edge positions relative to the water redox potential levels are significantly influenced by the material[1,2,21], crystal structure[22,23], surface characteristics[16,24,25,26], and operating environment of a photocatalyst[27,28]
In conclusion, this study first argues and reveals the large discrepancy in the EV and EC of transition metal oxides (TMOs) experimentally measured in vacuum and in an aqueous solution
Summary
The conduction and valence band edges (EC and EV) of a material relative to the water redox potential levels are critical factors governing photocatalytic water splitting activity. First-principles density functional theory (DFT) studies have been used to predict the environment-dependent band edge positions of various surfaces by investigating the electronic structure of slabs with surfaces in contact with a vacuum layer This idea is based on the assumption that the band edge positions of a material stay the same before and after contact with the electrolyte, i.e., that the band edges measured in vacuum can represent those in an operating environment. Cheng et al.[19] and Kharche et al.[20] performed ab initio molecular dynamics (MD) simulations with explicit water to explore the band edge positions in an aqueous solution These materials are primarily non-TMOs, and paramagnetic, and do not have complex magnetic configurations and Hubbard U correction parameters (Ueff). A systematic understanding of the roles played by spin polarization and Ueff on the results of calculations of oxides in explicit solvent have yet to be developed
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
