Oral Presentation Royal Australian Chemical Institute National Congress 2026

Structural Instabilities and Emergent Polarity in Photocatalytic BiVO₄ (136238)

Brendan J Kennedy 1 , Frederick P Marlton 2
  1. The University of Sydney, Camperdown, NSW, Australia
  2. Centre for Clean Energy Technology, School of Mathematical and Physical Sciences, University of Technology Sydney, Sydney, NSW, Australia

A detailed investigation of the temperature- and pressure-dependent local and long-range structure of BiVO₄, one of the most extensively studied materials in contemporary materials science is presented.1, 2 BiVO₄ is a promising photocatalyst for water splitting due to its favourable band gap, high chemical stability, and suitable band-edge positions, and has also been explored as a microwave dielectric material.

BiVO₄ undergoes a reversible second-order ferroelastic phase transition at ~528 K from the monoclinic fergusonite structure (mf-BiVO₄) to the tetragonal scheelite structure (ts-BiVO₄), driven by a q ≈ 0 soft optical Bg phonon mode. An analogous transition occurs under pressure at ~1.5 GPa. This transition involves changes in the distortion of the BiO₈ and VO₄ polyhedra, with the Bi–O bond environments evolving from four distinct bond lengths to two, and the V–O bonds from two distinct lengths to one.

DFT studies show that the Bi 6s² lone pair electrons and V⁵⁺ d⁰ cations enhances orbital hybridisation, reducing the band gap and enabling visible-light absorption with a conduction band edge near the thermodynamic H₂ evolution potential.3 Conventional DFT approaches struggle to reproduce the experimentally observed room-temperature mf structure, with the PBE functional predicting the high-symmetry ts phase to be energetically favoured.4 This is consistent with predictions from the Bastide phase diagram for ABX₄ compounds based on ionic radii.  The structural distortions distinguishing fergusonite from scheelite are comparatively subtle in BiVO₄ relative to other AIIIBVO₄ materials.

Despite its centrosymmetric structure, studies of BiVO₄ ceramics 5 and thin films6 have reported polar domains, polar domain walls, and phenomena including flexoelectricity, piezo-photocatalysis, and anomalous photovoltaic effects. These observations motivate a comprehensive structural re-examination. We employed variable-temperature and high-pressure X-ray and neutron scattering to probe both short- and long-range structural responses in BiVO₄ and to clarify the structural origins of these unexpected polar behaviours.

  1. Mullens, B. G.; Marlton, F. P.; Brand, H. E. A.; Maynard-Casely, H. E.; Everett, M.; Tucker, M. G.; Van Auken, E. R.; Manjon-Sanz, A. M.; Baldinozzi, G.; Vornholt, S. M.; Chapman, K. W.; Kennedy, B. J., The Local-Scale Origin of Ferroic Properties in BiVO4. Journal of the American Chemical Society 2025, 147 (9), 7840-7848.
  2. Lee, D.; Wang, W.; Zhou, C.; Tong, X.; Liu, M.; Galli, G.; Choi, K.-S., The impact of surface composition on the interfacial energetics and photoelectrochemical properties of BiVO4. Nature Energy 2021, 6 (3), 287-294.
  3. Sun, S.; Wang, W.; Li, D.; Zhang, L.; Jiang, D., Solar light driven pure water splitting on quantum sized BiVO4 without any cocatalyst. ACS Catalysis 2014, 4 (10), 3498-3503
  4. Liu, T.; Zhang, X.; Guan, J.; Catlow, C. R. A.; Walsh, A.; Sokol, A. A.; Buckeridge, J., Insight into the fergusonite–scheelite phase transition of ABO4-type oxides by density functional theory: A case study of the subtleties of the ground state of BiVO4. Chemistry of Materials 2022, 34 (12), 5334-5343
  5. Munprom, R.; Salvador, P. A.; Rohrer, G. S., Polar Domains at the Surface of Centrosymmetric BiVO4. Chemistry of Materials 2014, 26 (9), 2774-2776.
  6. Peng, R.-C.; Cheng, X.; Shao, P.-W.; Xue, F.; Chu, Y.-H.; Chen, L.-Q.; Zhou, Y., Ferroelastic twin domain patterns and polar domain walls of BiVO4 thin films via phase-field simulations. Acta Materialia 2023, 259, 119297.