(010) surface in single crystals and epitaxially grown samples: A joint first-principles and experimental effort*

As a prototypical oxide for water photocatalysis, BiVO₄ has many advantageous optoelectronic properties, including strong absorption in the visible and a favorable band alignment with water. However, its use as a photo-absorber is limited by its inefficient charge dynamics, especially at interfaces. Here, we present an integrated experimental and computational study aimed at an atomistic understanding of the surface morphology and electronic properties of BiVO₄ as a function of oxygen vacancy concentration.

We carried out first-principles calculations with Quantum Espresso (www.quantum-espresso.org/) and XPS/UPS measurements to obtain work functions and band alignments with vacuum. We show that oxygen vacancies at the surface behave differently from their bulk counterpart, in terms of formation energy and transport of small polarons. We also compare single-crystalline and epitaxially-grown samples, with focus on the relation among oxygen vacancies, electronic structure, and growth techniques. Finally, based on a combined study of measured and STM microscopy images, we propose how varying surface termination may help tune the photoelectrochemical performance of BiVO₄.