Photocatalysis-induced electric fields: Enhancing dichromate transport and reduction

Photocatalysis-induced phenomena, such as active motion and superhydrophilicity, have been widely studied [1,2]. In this presentation, we introduce a previously unrecognized effect: photocatalysis-induced electric fields [3]. Using monoclinic bismuth vanadate (BiVO4) films and potassium dichromate (K2Cr2O7) as a model reduction system, we demonstrate that illumination generates long-range electric fields extending hundreds of micrometers into the surrounding solution. Spatially resolved concentration measurements and transport analysis reveal that these fields strongly bias the migration of charged reactants toward the photocatalyst surface. The same behavior is observed in an independent system based on TiO2, indicating that this phenomenon is not limited to a specific material or crystal structure.

Unlike the localized interfacial fields commonly discussed in semiconductor heterojunctions, these extended electric fields enhance dichromate transport by more than three orders of magnitude, thereby maintaining a continuous reactant supply. As a result, the overall photocatalytic reduction rate is significantly improved without additional energy input, catalyst restructuring, or complex reactor engineering. We argue that photocatalysis-induced electric fields represent a new handle for coupling light-driven redox chemistry with ion transport. This concept opens an unexplored design space for optimizing photocatalytic reactors and may be generalizable to other oxidation or reduction processes relevant to green synthesis, solar fuel production, and environmental catalysis.

References

[1] K. Villa, M. Pumera. Fuel-free light-driven micro/nanomachines: artificial active matter mimicking nature. Chem. Soc. Rev., 2019, 48: 4966-4978.

[2] A. Fujishima, X. Zhang, D.A. Tryk. TiO₂ photocatalysis and related surface phenomena. Surf. Sci. Rep., 2008, 63: 515-582.

[3] C. Chen, S. Zhao, B. Zhou, C. Ye, B. Jiang, L. Zhang. Enhancing dichromate transport and reduction via electric fields induced by photocatalysis. iScience, 2025, 28.