Resistive hydrogen sensing response of Pd-decorated ZnO “nanosponge” film

Hydrogen (H2)-induced resistive response of palladium (Pd)-decorated zinc oxide “nanosponge” (Pd/ns-ZnO) 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 ∱/45 nm nanoclusters embedded in an amorphous matrix. After annealed at 500 °C for 1 h, the film was found to contain loosely connected 13 nm crystallites and had a porosity of 73%. The Pd/ns-ZnO film sensor at 20 °C showed a sensor response of 82 and a response time of 1 s for 2% H2. After heated slightly to 80 °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 °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.