Enhanced gas selectivity induced by surface active oxygen in SnO/SnO2 heterojunction structures at different temperatures.

The development of heterojunction structures has been considered as an important step for sensing materials. In this report, 3D hierarchical SnO-SnO2 heterojunction structures were synthesized and developed via simple one-pot hydrothermal synthesis without any extra processes. The prepared 3D samples exhibit high sensitivity, benefiting from the synergistic effects of SnO and SnO2. Interestingly, SnO-SnO2 hybrid structures exhibited distinctly different sensitivities at 180 and 280 °C, and the sensitivity can achieve values of 47.69 and 41.56 toward ethanol and acetone, respectively, at concentrations of 100 ppm. A mechanistic analysis of the sensitivity and concentration-dependence revealed that the oxygen species on the surface were O- and O2- at different temperatures. Therefore, the temperature selectivity of the sample may be due to the different activities of the active oxygen species. Moreover, the composition also shows excellent stability at operating temperatures. The high sensing sensitivity and selectivity is promising for practical VOC gas detection; this also offers a new perspective for the design of multifunctional sensing materials.