Addressing low-occurrence problems from low concentrations,
we
demonstrate amorphous TiO2–0.5x(OH)x nanofilms (amT) that feature abundant
hydroxyl groups (of bulk and surface) for formaldehyde oxidation under
UVC irradiation. Such hydroxyl groups can significantly enrich bound
water (of adsorbed and produced) and formaldehyde at a hydration layer
on the surface. With this structure, mechanistic insights and reaction
kinetics are correlated. Compared to the anatase one (anT), our amT
exhibits a remarkable decrease in the recombination of charge carriers,
complete formaldehyde oxidation even at dry conditions, a nearly zero-order
reaction that elucidates the approximately independent kinetics, and
an unprecedentedly 104-fold increase in the reaction rate.
Based on photoluminescence and Fourier transform infrared spectroscopy,
light indispensability and moisture enhancement to formaldehyde oxidation
are corroborated. Consequently, due to abundant hydroxyl groups, the
mass transfer (of formaldehyde and water) at its hydration layer is
strengthened, as evidenced by the mechanistic insights; hence, fascinating
kinetics is achieved for environmental applications in practice.