Unfolding the Impact of H2-Reduction Treatment in Enhancing the Photocatalytic Activity of Rutile TiO2 Based on Photocarriers Dynamics

In the pursuit of efficient titania photocatalysts forwater splitting,several strategies have been employed. One of these is reduction oftitania (TiO2) via treatment under hydrogen atmosphere,a promising technique to improve the photocatalytic performance. Ithas been proposed that electron injection induced by reduction onTiO(2) demonstrated an improved photocatalytic activity(.) However, the dynamical processes involving the photogeneratedcharge carriers in reduced TiO2 have not been fully exploredand understood yet. In this work, we employ time-resolved absorptionspectroscopy (TAS) and photoluminescence (PL) measurements to unravelthe impact of H-2 reduction treatment on the photocarriersin rutile TiO2 (R-TiO2). TAS results revealedthat the photoexcited electrons are preferentially filling the shallowertrap states of reduced R-TiO2, with the lowest energy limitof similar to 0.25 eV below the conduction band minimum, much shallowerthan that of nonreduced R-TiO2 (similar to 0.62 eV). Furthermore,these favorable effects of H-2-reduction resulted in notableincrease of long-lived shallow-trapped electrons, substantially extendingthe lifetimes of electrons and holes. PL measurements strongly supportthe positive impact of H-2 reduction treatment: the NIRemission (similar to 850 nm) is largely quenched, indicating that theradiative recombination of deep trapped electrons and holes is significantlyreduced. The combined PL and TAS results shed light on the impactof H-2 reduction on R-TiO2, and this strategycan be potentially useful for further development of other photocatalyticmaterials.

Automated summary

This study investigates the impact of hydrogen reduction treatment on the photocarriers in rutile TiO2. The results reveal that the reduction treatment leads to filling of shallower trap states, extended lifetimes of electrons and holes, and reduced radiative recombination. This strategy can potentially be applied to other photocatalytic materials.