Electric Field Manipulation for Improved Rates of Photocatalysis by Mesoporous TiO₂

This work demonstrates a concept for improving rates of photocatalysis by mesoporous thin films of semiconducting oxide nanoparticles through manipulating the built-in electric field near the nominal free surface. The reaction rate increases via combinations of donor concentration and surface potential that yield wide space charge widths and correspondingly large regions encompassed by the built-in field. The field draws minority carriers generated deep within the film toward the nominal surface where the chemical reactant is most concentrated. In the photo-oxidation of aqueous methylene blue by anatase TiO₂, optimization of the parameters increases the rate by nearly a factor of 3. The concept should extend to many photocatalytic materials and reactions.