Site-selective XAFS spectroscopy tuned to surface active sites of Cu/ZnO and Cr/SiO2 catalysts

XAFS (X-ray absorption fine structure) spectra were measured by using the f luorescence spectrometer for the emitted X-ray from sample. The chemical sh ifts between Cu-0 and Cu-I and between Cr-III and Cr-VI were evaluated. Tun ing the fluorescence spectrometer to each energy, the Cu-0 and Cu-I site-se lective XANES for Cu/ZnO catalyst were measured. The first one was similar to the XANES of Cu metal and the second one was the 5 : 5 average of XANES for Cu-I sites + Cu metal. The population ratio of copper site of the Cu/Zn O catalyst was found to be Cu metal : Cu2O : Cu-I atomically dispersed on s urface = 70(+/-23) : 22(+/-14) : 8(+/-5). Site-selective XANES for Cr-III s ite of Cr/SiO2 catalyst was also studied.