Bifunctional Sensing Mechanism of SnO₂–ZnO Composite Nanofibers for Drastically Enhancing the Sensing Behavior in H₂ Gas

SnO₂–ZnO composite nanofibers fabricated using an electrospinning method exhibited exceptional hydrogen (H₂) sensing behavior. The existence of tetragonal SnO₂ and hexagonal ZnO nanograins was confirmed by an analysis of the crystalline phase of the composite nanofibers. A bifunctional sensing mechanism of the composite nanofibers was proposed in which the combined effects of SnO₂–SnO₂ homointerfaces and ZnO–SnO₂ heterointerfaces contributed to an improvement in the H₂ sensing characteristics. The sensing process with respect to SnO₂–ZnO heterojunctions is associated not only with the high barrier at the junctions, but also the semiconductor-to-metallic transition on the surface of the ZnO nanograins upon the introduction of H₂ gas