Toluene Adsorption on CeO2 (111) Studied by FTIR and DFT

Abstract

The adsorption of toluene on cerium oxide was investigated by using in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and density functional theory (DFT) calculations. It is shown that the toluene molecule undergoes dissociative adsorption with the loss of a hydrogen atom from the methyl group and the generation of both, a benzyl (C6H5–CH2−) and a surface hydroxyl species. Characteristic infrared signals are observed due to the formation of a methylene group at 2800 cm−1 (ν CH2) and 1300 cm−1 (δ CH2). All vibrational modes were identified combining DFT calculations of the optimized system and experimental evidences. An adsorbed stable benzyl structure was identified with a binding energy of about − 0.65 eV, which supports the experimental findings. Temperature programmed surface reaction followed by DRIFTS and mass spectrometry showed that benzyl species are oxidized by lattice oxygen to benzoate, formate and, finally, to CO and CO2. Understanding the reactivity of ceria surfaces is key to improve the performance of combustion catalysts for volatile organic compounds abatement.