Hierarchical Nb2O5@ZnO hetero-branched nanorods for enhanced H2S gas sensing

Hierarchical Nb2O5@ZnO hetero-branched nanorods used for highly responsive, selective, and stable hydrogen sulfide (H2S) sensors were synthesized through a sequential process combining a hydrothermal method, atomic-layer-deposition processing, and modified hydrothermal processing for branching ZnO nanowires. The Nb2O5@ZnO hetero-branched nanorod sensors exhibited a great response (Ra/Rg) of 6.10 towards 20 ppm H2S at an optimal working temperature of 400 °C, whose resistance changing rate (∼5.10) was 39.2- and 1.9-fold those of Nb2O5 (∼0.13) and Nb2O5@ZnO core-shell nanorod (∼2.74) sensors, respectively. The heterojunction formed at the Nb2O5@ZnO interface and the characteristic reaction between ZnO and H2S effectively improved H2S sensing performance. Moreover, the branching of ZnO nanowires introduced abundant homojunctions and prominently enlarged the specific surface area, further increasing the response of hetero-branched sensors. Meanwhile, the Nb2O5@ZnO hetero-branched sensors maintained steady performance over a month, indicating good stability and repeatability. In a word, such hierarchical Nb2O5@ZnO hetero-branched nanorod gas sensors are promising for the development of sensitive and selective H2S detection.