Fast Response Palladium-based Hydrogen Sensor Fabricated By AAO Template

Hydrogen is an explosive gas. It could cause explosion when hydrogen concentration ranges from 4.65% to 74%(by volume mixed in air). When hydrogen gas leaks, hydrogen sensor must response in a short time. Fast response can ensure enough time for people to retreat to safe place. Below is the main work:(1)Anodic aluminum oxide(AAO) template was fabricated by a two-step anodic oxidation method. The average pore-size ranges from 70 to 80 nm. The distance between two pores is about 130 nm. AAO was fabricated using 99.99% and 99.999% aluminum foil separately. Pores are better arranged on the high-purity aluminum. And the pore sizes are more uniform.(2)Hydrogen sensor based on palladium film supported by AAO template was studied. The typical response of the Pd film on AAO was 20 times faster than the dense Pd film on Al foil. It is demonstrated that the Pd film on AAO is nanoporous. And the specific surface is larger.( 3) The influence of deposition rate, substrate temperature and annealing temperature on the sensor was studied. The results showed that at lower deposition rate, the response and recovery was faster; Low-temperature deposition helps enhance hydrogen absorption; The best anneal temperature is 200 ℃ for the nanoporous Pd film. In this sensor, we obtained a sensor response time as short as 30 s. The recovery time is about 2 min. However, an unexpected slow response appears for the nanoporous Pd films annealed above 300 ℃.(4)AAO template was etched by phosphoric acid solution to widen the pores. After 30 min, the average pore size grows from 70 nm to 80 nm. But after 60 min, the walls were etched through. If the AAO template with 80 nm pores is selected, the shortest response time is 20 s. And the shortest recovery time is about 1.5 min. However, when the walls of the AAO template is discontinous, the response and recovery slows down.