Correlation of Relative X-ray Photoelectron Spectroscopy Shake-up Intensity with CuO Particle Size

X-ray photoelectron spectroscopy (XPS) analysis of four Cu/SiO2 catalyst systems of different particle sizes of CuO on the surface showed variation in the relative peak area intensities of the shake-up lines to main core levels of the Cu 2p orbitals. These differences were attributed to various degrees of XPS-induced reduction of CuO initially formed on the surface by spin coating copper(II) acetate {Cu(CH3CO2)2·H2O, Cu(ac)2} solutions of varying concentration. Changes in Cu L3M4,5M4,5 X-ray excited Auger (XAES) line shapes under time-dependent exposure to the soft Mg Kα X-rays revealed that smaller particle sizes were more susceptible to reduction to Cu(+1) than larger ones. The degree of reduction of Cu(+2) to Cu(+1) correlated with measured atomic force microscopic (AFM) particle heights of CuO on these substrates prior to XPS.