Abstract
Although step structures have generally been considered to be active sites, their role on a TiO2 surface in catalytic reactions is poorly understood. In this study, we measured the contact potential difference around the steps on a rutile TiO2(110)-(1 × 1) surface with O2 exposure using Kelvin probe force microscopy. A drop in contact potential difference was observed at the steps, indicating that the work function locally decreased. Moreover, for the first time, we found that the drop in contact potential difference at a <1−11> step was larger than that at a <001> step. We propose a model for interpreting the surface potential at the steps by combining the upward dipole moment, in analogy to the Smoluchowski effect, and the local dipole moment of surface atoms. This local change in surface potential provides insight into the important role of the steps in the catalytic reaction.
Highlights
Titanium dioxide (TiO2) has attracted considerable interest for its promising applications as a photocatalyst and as catalyst support, as well as in gas sensors [1,2,3,4,5,6,7]
We discuss a possible origin of the change in contact potential difference (CPD) and propose a simple model for interpreting the local surface potential at the steps with the help of surface charge redistribution, in analogy to the Smoluchowski effect, and the local dipole moment of surface atoms supported by the Density functional theory (DFT) simulation
The CPD image shows that the CPD decreases at the steps, indicating that the work function locally decreases at the steps
Summary
Titanium dioxide (TiO2) has attracted considerable interest for its promising applications as a photocatalyst and as catalyst support, as well as in gas sensors [1,2,3,4,5,6,7]. TiO2(110) surfaces with O2 exposure using KPFM and observed the drop in CPD at the steps, indicating that the work function locally decreased.
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