Electronic Interaction between Metal Additives and Tin Dioxide in Tin Dioxide-Based Gas Sensors

Abstract

The electronic interaction of SnO₂ with Ag and Pd particles dispersed on its surface was examined by means of X-ray photoelectron spectroscopy (XPS). The binding energies (BE) of Sn3d and O1s of Ag(1.5 wt%)-SnO₂ and Pd(3.0 wt%)-SnO₂, which were lower by 0.5–0.7 eV than those of pure SnO₂ in the as-prepared state, shifted reversibly by reduction and oxidation treatments. These shifts in BE are shown to reflect the shifts of Fermi energy of SnO₂ which are interacting electronically with the metal additives. The electronic interaction depended on the metal loading, being strongest at 1.5 wt% and 3.0 wt% loadings of Ag and Pb, respectively. The implication is that the electronic interaction is of primary importance to the inflammable gas detection by Ag-SnO₂ sensors.