View article

We employed transient absorption spectroscopy (TAS) to investigate the kinetic dependences of photocatalysis in anatase and rutile TiO₂ films of varying morphology. In mesoporous films, anatase was ∼30 times more efficient than rutile in the photocatalytic degradation of an intelligent ink model system. Independent of phase, up to 100 lower levels of photocatalysis were found in dense films. Charge carrier lifetimes were probed by TAS on the microsecond to second time scale. For both rutile and anatase, recombination was independent of morphology. Rutile exhibited up to 10 times slower recombination kinetics than anatase. Efficient, irreversible hole scavenging by alcohols was present in mesoporous anatase alone, resulting in the generation of long-lived electrons (τ ≈ 0.7 s) which, upon the addition of the dye reduction target resazurin, enabled efficient electron transfer (τ ≈ 3 ms). Hole scavenging by …