Grain-Size-Tuned Highly H 2 -Selective Chemiresistive Sensors Based on ZnO–SnO 2 Composite Nanofibers

We investigated the effect of grain size on the H2-sensing behavior of SnO2-ZnO composite nanofibers. The 0.9SnO2-0.1ZnO composite nanofibers were calcined at 700 °C for various times to control the size of nanograins. A bifunctional sensing mechanism, which is related not only to the SnO2-SnO2 nanograins, but also to the ZnO-SnO2 nanograins with surface metallization effect, is responsible for the grain-oriented H2-sensing properties and the selective improvement in sensing behavior to H2 gas compared to other gases. Smaller grains are much more favorable for superior H2 sensing in SnO2-ZnO composite nanofibers, which will be an important guideline for their use in H2 sensors. The one-dimensional nanofiber-based structures in the present study will be efficient in maximizing the sensing capabilities by providing a larger amount of junctions.