The catalytic water formation reaction on Pt(111) was investigated by time-resolved near-edge X-ray absorption fine structure (time-resolved NEXAFS) experiment and kinetic Monte Carlo (KMC) simulation. An oxygen covered Pt(111) surface with the (2×2) structure was exposed to gaseous hydrogen (5.0×10−9 Torr) at 130 K. O K-edge NEXAFS spectra were measured during the reaction with a time interval of 35 s. Quantitative analyses of the spectra provided the coverage changes of the reaction species (O, OH, and H2O). KMC simulation has well reproduced the reaction kinetics obtained by the NEXAFS experiment. The surface configurations also clearly reproduced the reported STM results, which show that the OH reaction fronts proceed on the O-covered Pt(111) surface by producing H2O islands backwards. The KMC simulation also revealed that proton transfer between H2O and OH plays a significant role for the propagation of the reaction fronts.
