Enhancing dichromate transport and reduction via electric fields induced by photocatalysis.

Mass transport is a fundamental yet often overlooked factor in influencing adsorption and photocatalytic reaction kinetics. This study examines the role of mass transport using the model system of monoclinic bismuth vanadate (BiVO) films and potassium dichromate (KCrO) in a representative photocatalytic reaction. We show that diffusion-driven delivery of KCrO to the BiVO surface increases adsorption capacity but decreases the adsorption rate constant. Notably, during the model photocatalytic reduction, long-range electric fields were observed around the illuminated BiVO films, a phenomenon also confirmed in a separate reaction system using TiO as the photocatalyst. These electric fields, distinct from the localized fields formed within heterojunctions, enhance dichromate transport by more than three orders of magnitude. This enhanced transport ensures a continuous supply of reactant to the photocatalyst, significantly improving reaction efficiency without additional energy input. These findings introduce a new strategy for optimizing photocatalytic processes, offering broad insights for advancing sustainable chemical engineering applications.