Surface chemistry of chromia-pillared tin and zirconium phosphate materials: an X-ray photoelectron spectroscopic study

Abstract

X-Ray photoelectron spectroscopy has been used to examine the surface chemical composition of chromiapillared Sn and Zr phosphates. All the materials are single-phase with Cr^III ions octahedrally coordinated in a virtually anhydrous phosphate network, independent of the chromium content and preparation conditions. Quantitative analysis of the surfaces of the materials was achieved within an accuracy of ±5%. While the atomic ratios M_i:M_j(M_i,M_j= Cr, P, Sn, Zr) differ by at most 20% from the chemical composition of the starting materials, the nO:nM_i(M_j) atomic ratios show a sizeable depletion (up to 50%) in oxygen content, which we interpret as being due to surface dehydration.