Insights into TiO2 thin film photodegradation from Kelvin Probe AFM maps

The synthesis of TiO2 thin films by the chemical spray pyrolysis method at different titanium isopropoxide (TTIP) to acetylacetone (AcacH) ratios has been shown to lead to the highest photodegradation at 1 (TTIP):8 (AcacH). These films hold promise in the field of indoor pollution treatment. Carbon incorporation into the surface and into the TiO2 lattice could be responsible for the observed performance, but the mechanism is still to be elucidated. Here, we report the correlation of contact potential difference (CPD) contrast maps as produced using Kelvin Probe Force Microscopy, and the observed functionality dependence on the TTIP to AcacH ratio. Since the CPD contrast locally provides information about the sample's Fermi level, this correlation provides a means to interpret enhanced photocatalytic activity in terms of the presence of acceptors that make possible a faster transfer of charge carriers to the surface.