Figure 6

Shirley background-subtracted XPS spectra in the Fe region of green sites (a,c,f,h), yellowish-green sites (b,d,g,i) and reddish-brown site (e). The black, red, green and blue peaks represent octahedral Fe²⁺, octahedral Fe³⁺, satellite Fe²⁺ and satellite Fe³⁺, respectively.