Exploring the structural conditions favoring Au anionic behavior on Au doped CeO₂

In this work, we conducted a systematic study of the synthesis and structural and chemical characterization of Au-doped CeO₂ materials to identify the conditions under which the anionic character of gold is observed, using both experimental and density functional theory simulations. Successful incorporation of Au into the samples was detected from infrared spectra and X-ray diffraction analysis. As the Au concentration increased, an increase in defects and a reductive chemical environment was observed using UV-vis spectra. The presence of Au loading onto CeO₂ as particles in the high Au concentration samples was determined with SEM images and EDS spectra. The Au adsorption on the CeO₂ (111) surface was found to be the most stable by means of DFT modeling. The most stable Au adsorption models incorporated an oxygen vacancy and Au substituting an oxygen atom. Further Bader charge analysis revealed that Au had a negative character in these models. X-ray induced photoelectron spectra uncovered that in the low mol% concentration regime, there is a presence of anionic Au behavior. Further high-resolution window chemical species quantification and correlation confirmed that anionic character was promoted by Au substituting oxygen atoms as pointed out by DFT calculations, implying that anionic gold was present and has indeed previously not been contemplated in Au-doped CeO₂ applications.