Interaction of NO with nanosized Ru-, Pd-, and Pt-doped SnO2:: Electron paramagnetic resonance, Mossbauer, and electrical investigation

The mechanism of NO interaction with nanosized Ru(Pd,Pt)-doped SnO2 was studied by electron paramagnetic resonance, Mossbauer, and electric resistance measurements. Three steps were proposed for the reaction between the semiconductor oxide and the gaseous component: (i) the formation of bielectronic oxygen vacancies (V-0(circle)) in SnO2; (ii) their single-ionization (V-0(circle)) with injection of electrons into the SnO2 conduction band; (iii) the subsequent transfer of electrons from V-0(circle) to [Ru(Pd,Pt)](4+). The last process induces the formation of further oxygen vacancies which reduce the transition metal centers to lower oxidation states; the redox processes is enhanced and the electrical resistance in transition metal-doped SnO2 is stronger modified with respect to the undoped material.