Catalytic decomposition reaction of formic acid on an Ar+-bombarded TiO2(110) surface : steady-state kinetics and microscopic surface structure

Abstract

The kinetics of the catalytic decomposition reaction of formic acid (DCOOD) were examined under steady-state conditions on Ar⁺-bombarded and partially annealed TiO₂(110) surfaces characterized by scanning tunnelling microscopy (STM), Auger electron spectroscopy (AES), low-energy electron diffraction (LEED), X-ray photoelectron spectroscopy (XPS) and UV photoelectron spectroscopy (UPS). The bombarded surface was rugged and contained a certain number of reduced Ti³⁺ cations. The (1 × 1) terraces covered the surface annealed at 900 K, while the reoxidation of the Ti³⁺ cations occurred on the surface annealed at 500 K and was completed at 700 K. The catalytic dehydration and dehydrogenation reactions of formic acid were observed regardless of the annealing history of the bombarded surface. The catalytic performance of the coordinatively unsaturated Ti³⁺ sites in the decomposition reaction was compared with that of the well ordered (1 × 1) surface.