Application of differential charging for analysis of electronic properties of supported silver

The electronic properties of silver supported on α-alumina (ethylene epoxidation catalysts) have been studied by X-ray photoelectron spectroscopy. It has been shown that treatment of the fresh catalyst in C 2H 4 + O 2 reaction mixture increases the Ag3d 5 2 core level binding energy (BE). The observed variation of the BE(Ag3d 5 2 ) does not reflect a change in the initial state of silver from metallic, but is determined by the alteration in the differential charging of the supported silver compared with the support surface. The latter effect originates from the higher conductivity of the supported silver than of the dielectric support. Possible factors affecting the internal conductivity of the silver are discussed.