Studies Of Palladium-Silver Thin Film For Hydrogen Sensing

Hydrogen gas is joining electricity and fossil fuels as a primary energy source, with the superiority of higher energy efficiency and the absence of polluting emissions. Reliable, cheap, compact, and safe sensors are therefore in high demand to measure H₂ concentration in gas flows and to monitor gas leak during H₂ production, storage, transport and utilization. This is required not only for better control of H₂ involved processes, but for health and safety reasons as well.In this thesis, current progress on hydrogen sensing was summarized in detail (Chapter I), the fabrication of a micro Pd-Ag hydrogen sensor by MEMS techniques (Chapter II), and the sensing performance of the hydrogen sensor were studied and optimized (Chapter III).A zigzag-shaped microstructure of Pd-Ag was coated on a porous alumina substrate through a combination of microfabrication techniques including photolithography, thin film sputtering and electron beam vacuum evaporation. The sensing performance of the mixed metal film is much better compared with that of sheet palladium film fabricated through the same procedure. The Pd-Ag structure achieved high hydrogen sensitivity, short response time and good reproducibility at room temperature. The discontinuous Pd-Ag structure on porousα-Al₃O₂ substrate can improve the electric performance, enhance integration to the substrate and avoid hydrogen supersaturation of the sensing film, and the performance of sensor became more stabilized and reversible. Water vapor has no effect on the sensing performance of the sensor. The effects of Cu doping on the Pd-Ag sensing material toward hydrogen has also been investigated.The present sensor is very promising for room temperature hydrogen leakage detection and related applications.