Highly sensitive and selective H2 sensing by ZnO nanofibers and the underlying sensing mechanism.

We report, and propose a mechanism for, the exceptional hydrogen gas (H2) sensing ability of ZnO nanofibers. In comparison to SnO2 nanofibers, ZnO nanofibers show outstanding H2 gas response and unmistakable H2 selectivity. Different from the reducing gas effect observed in SnO2 nanofibers, a semiconductor-to-metal transition that occurs in the presence of H2 gas molecules is responsible for the exceptional response and selectivity of ZnO nanofibers to H2. Notably, the presence of nanograins within nanofibers further intensifies the resistance modulation observed due to this transition.