Here SnO₂/LaFeO_3−XN_X composite was fabricated using a wet chemical method and was applied to pollutants degradation and gas sensing for the first time. The composite exhibits high performance for photocatalytic degradation of Rhodamine B (RhB) dye and selectivity sensing of various gases. On the basis of the completed experiments, the improved RhB degradation and selective gas sensing performance resulted from the extended optical absorption via N₂ incorporated surface states and enhanced charge separation via coupling SnO₂. Using the scavengers trapping experiments, the superoxide radical (O₂^•−) was investigated as the major scavenger involved in the degradation of RhB over SnO₂/LaFeO_3−XN_X composite. In this paper, the probable reaction steps involved in the RhB dye degradation over SnO₂/LaFeO_3−XN_X composite are proposed. This work will provide reasonable strategies to fabricate LaFeO₃-based proficient and stable catalysts for environmental purification. In addition, the result of the selectivity of gas performance is also presented.

In order to investigate function of carrier behavior on gas-sensing properties, tin oxide-based films with different carrier concentration and mobility were obtained, by magnetron sputtering from the powder target, which was followed by further oxygen-management though the annealing treatment. The microstructure, surface morphology, electrical properties and gas sensitivity were characterized by XRD, Raman spectrum, photoluminescence spectrum, atomic force microscope, the hall effect system and electrochemical workstation, respectively. The results showed that all SnO₂-based films had a tetragonal rutile phase with (101) preferred orientation. The introduction of fluorine and regulation of oxygen vacancies tuned carrier concentration from 10¹⁵/cm³ to 10²¹/cm³ and mobility from 10² cm²/V·s to 10⁻¹ cm²/V·s. The decreasing carrier concentration as well as increasing mobility had a positively important function to improve the sensitivity of SnO₂-based films. The air-annealed SnO₂ film with lowest carrier concentration had a maximum sensitivity of R = 5.0, while vacuum-annealed SnO₂:F film with the highest carrier concentration being the minimum sensitivity. This puts forward a novel reference for the design and application of SnO₂-based gas sensing films.

The interaction of oxygen and fluorine (F&O) in an F-doped SnO₂ film, prepared by regulating oxygen partial pressure and the content of doped fluorine from 2.5 at% to 10 at%, was investigated in the large perspective through characterization methods including XRD, Raman spectroscopy, photoluminescence spectroscopy, wettability measurement and a Hall effect test system. The results show that F&O’s competitive and cooperative relationship would be reflected in the structure and electrical characteristics of SnO₂ films. The oxygen action is overwhelming and restricts fluorine, so a growing number of F atoms occupy the position by the order of co-edge oxygen of tin–oxygen octahedron chains > oxygen vacancies > segregation, which leads to that carrier concentration modestly increasing from ~10¹⁵ to ~10¹⁷/cm⁻³. As oxygen action is inadequate to restrain fluorine, more F atoms are likely to enter the SnO₂ lattice in a solid-solution way to replace the O atoms at the co-edge position of the octahedron chains, causing a dramatic increase in carrier concentration from ~10¹⁶ to ~10¹⁹/cm⁻³. Furthermore, by continuing to weaken oxygen action, only 2.5 at% of fluorine content could bring about a carrier concentration augment from ~10¹⁶/cm⁻³ to ~10¹⁸/cm⁻³, then going up to ~10²¹/cm⁻³ by post-annealing. However, the impairment of oxygen action contributes to a more effective doping of fluorine on SnO₂ film. Such mutual action between fluorine and oxygen provides a direction for highly efficient production and tunable regulation of SnO₂ film on demand.