Understanding the impact of BiVO4 surface facet and termination on infrared spectroscopy and oxygen evolution reaction

The infrared (IR) spectra of BiVO4 surfaces are sensitive to local atomic structure and can potentially provide insight into surface heterogeneity observed in recent spatially resolved nano-Fourier-transform infrared (nano-FTIR) spectroscopy measurements. However, no clear relationship has been established yet between IR spectral features and the surface atomic structures in BiVO4. Here, we used first-principles calculations to investigate the IR signatures of four low-index BiVO4 surface orientations with stoichiometric and Bi-rich terminations. We found that the most distinctive spectral feature is the symmetric stretching mode of VO43− units, which is present only on stoichiometric surfaces and exhibits facet-dependent frequency shifts and intensity variations. Analysis of the vibrational modes showed that these changes originate from differences in the magnitude and orientation of surface-induced V–O bond distortions relative to the surface normal direction. Comparison with experimental nano-FTIR spectra shows a consistent trend in the change of the symmetric stretching peak intensity across different surface facets, while discrepancies in the relative intensity ratio between asymmetric and symmetric stretching modes suggest additional contributions from experimental factors, including probe depth and tip orientation. Oxygen evolution reaction calculations further confirm the strong influence of surface orientation and termination on catalytic activity. These results establish a direct link between surface atomic structure, IR signatures, and catalytic behavior in BiVO4, providing a framework for interpreting nanoscale IR spectroscopy measurements of heterogeneous photocatalyst surfaces.