Vanadium-promoted tin oxide semiconductor carbon monoxide gas sensors

The semiconductor gas sensors investigated are constituted by vanadium-tin oxide nanoparticles, prepared by a co-precipitation method. They were evaluated for carbon monoxide detection at low temperatures. The sensing characteristics obtained are associated with the composition, structure and surface state of oxide semiconductor. XPS analysis revealed an electronic interaction between Sn and V atoms in the mixed oxide structure and the formation of vanadium cations with multiple valences. Combined XRD and FTIR analyses showed that the tin oxide crystallinity decreased with increasing vanadium loadings. Lower levels of vanadium dopants in tin oxide enhanced response to CO gas in air because they facilitated oxygen adsorption by scavenging electrons to form reactive oxygen ions on the surface, as indicated by electrical and EPR measurements. The response to CO gas in nitrogen atmosphere was observed, and increased with increasing CO concentrations. Sensing mechanisms that discuss the roles of the vanadium redox pairs and oxygen vacancies in the CO detection process are proposed.