Temperature‐Programmed Reflection Absorption Infrared Spectroscopy: A Methods Review

Abstract

AbstractA method is proposed to measure the kinetics of elementary‐step reactions using reflection‐absorption infrared spectroscopy (RAIRS) by slowly ramping the sample temperature while continually collecting the interferograms, where the interferograms are post‐processed to provide temperature‐dependent spectra. Heating rates of ~10−2 K/s allow spectra to be collected so that the temperature is essentially constant for each spectrum. This strategy can allow short‐lived intermediates to be observed. The data are fit to analytical formulae similar to those used for conventional temperature‐programmed desorption and the two approaches are complementary. The method is illustrated by measuring the activation energy for the ordering of crystalline thin films and for multilayer desorption. The utility of the approach for measuring surface‐chemical processes is illustrated for the dimerization kinetics of a prochiral reactant, methyl pyruvate (CH3CCO2CH3), on Pd(111), where the monomer has been found to be more reactive than the dimer, and the decarbonylation steps of furfural (C4H3O ⋅ CHO), a product of the treatment of biomass. The results are in good agreement with cases in which there are other methods for measuring the reaction rates. The approach is also useful for establishing how accurate the results of theoretical simulations are for elementary surface reactions.