(Pritzker School of Molecular Engineering, University of Chicago & Istituto CNR di Chimica dei Composti Organometallici, Pisa)
 

Abstract:

Bismuth vanadate (BVO) is a promising photoanode for photoelectrochemical cells, due to its tunable band gap (~2.4 – 2.6 eV), favorable alignment of its valence band with the water oxidation potential, stability in aqueous environments, and its relative easiness of preparation ^[1]. In a recent study ^[2], we showed that tuning surface termination/composition and hence surface energetics is critical to improve the efficiency of the oxygen evolution reaction (OER) ^[2]. In addition, we highlighted ^[3] the importance of surface defects in altering the reactivity of BVO toward water, concomitant to water modifications to the electronic structure of the photoanode. However, a complete atomistic description of the interface between defective facets of BVO and water is not yet available, and yet it is necessary for the optimization of the OER efficiency. Here we carry out first principles molecular dynamics simulations with the Qbox code (http://qboxcode.org/) of BVO-water interfaces with different composition, as well as measurements of the electronic (XPS) and vibrational (IRRAS) spectra of water-covered BVO thin films. We combine theoretical and experimental results on spectra and computed electronic properties to characterize the interplay between surface hydroxylation and metal oxidation states at the surface, and to understand their impact on surface reactivity.

^[1] T. W. Kim and K.-S. Choi, Science (2014).
^[2] D. Lee, W. Wang et al. Nat. Energy (2020).
^[3] W. Wang et al. J. Am. Chem. Soc., (2022).
 

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