Resistive hydrogen sensing response of Pd-decorated ZnO nanosponge film

Hydrogen (H-2)-induced resistive response of palladium (Pd)-decorated zinc oxide nanosponge (PdinsZnO) film was studied at different operation temperatures with and without UV illumination. The as deposited ns-ZnO film, fabricated using a supersonic cluster beam deposition system, was highly porous and composed of similar to 5 nm nanoclusters embedded in an amorphous matrix. After annealed at 500 degrees C for 1 h, the film was found to contain loosely connected 13 nm crystallites and had a porosity of 73%. The Pd/nsZnO film sensor at 20 degrees C showed a sensor response of 82 and a response time of 1 s for 2% H-2. After heated slightly to 80 degrees C, the sensor response was increased by 43 times, and the response and recovery times dropped to 0.3 s and 18 s, respectively. This performance is superior to those of many other metal oxide nanomaterials operating at temperatures > 200 degrees C. The sensing properties of the Pd/ns-ZnO film showed little degradation when UV illumination was applied, but the sensing stability was improved. A reaction model was proposed to give an explanation to the gas sensing process. The influences of increasing the operation temperature and UV illumination are discussed. (C) 2017 Elsevier B.V. All rights reserved.