Hydrocarbon sensing mechanism of surface ruthenated tin oxide: An in situ IR, ESR, and adsorption kinetics study

In this study we explain the conductivity changes involved in the sensing m echanism of surface ruthenated tin oxide toward butane. The adsorption free energy is found to be higher for surface ruthenated tin oxide (DeltaG = -6 4.85 kJ/mol) as compared to pure tin oxide (DeltaG = -50.2 kJ/mol) implying that the gas adsorbs faster on the ruthenated sample. The ESR studies indi cate that butane preferentially adsorbs on the Ru sites, while the IR studi es explain the nature of the adsorbed species. A scheme based on these stud ies is proposed, where surface acetate species is formed on the surface rut henated tin oxide upon adsorption of butane at 300 degreesC, while the elec tronic conduction in these sensors is attributed to the formation of surfac e states.