Delta-mu XANES reveals the electronic structure of the adsorption of propene on gold nanoparticles

Abstract

Experimental XANES and delta-mu analysis by Nijhuis et al. (2008) have shown that propene adsorption, with pi back-bonding, on gold inhibits the hydrogen oxidation rate in the hydro-epoxidation of propene on gold nanoparticles. In spite of the smallness of the features, delta-mu analysis proved its usefulness in accessing the reaction path. Details of the mechanism are still to be elucidated. The availability of accurate XANES simulation codes enables further analysis. In this work XANES simulations with FEFF9 reproduce the delta-mu spectra for the H oxidized and the propene co-fed Au nanoparticles. The calculations evidence a propene with pi back-bonding to the Au, and bound at defects or steps or in very small Au nanoparticles. The charge on the nanoparticle was analyzed, and the cationic, or even better, the neutrally charged Au nanoparticles reproduce the experiments on the propene co-fed catalyst. Thereby, this work theoretically supports the experimental findings of Nijhuis et al. (2008) and Chen et al. (2013).