Research PaperAerobic and anaerobic H2 sensing sensors fabricated by diffusion membranes depositing on Pt-ZnO film

- A method of combining chemical vapor deposition (CVD) and ultrasonic spray pyrolysis (USP) was applied to deposit SiO2/Al2O3 composite membrane in-situ on the Pt-modified ZnO sensing film. And membranes of different Si/Al ratios could adjust the oxygen diffusion.
- The sensors acquire high H2 responses under 10,000 ppm and 50 ppm oxygen concentration.
- The recovery time was evaluated with a method which allowed us to observe the continuous change in resistance intuitively.
- Pt-modified ZnO exhibits low response to H2 in high oxygen concentration and high response in low oxygen concentration. This shows the high oxygen activity of Pt-modified ZnO, which is contrary to the traditional idea.
- A high throughput gas testing network was used to test the sensing properties of several sensors at the same time.

Utilizing sensor to detect H2 under different oxygen concentrations is essential in monitoring status of nuclear weapon. A membrane covering on a sensing film could influence the diffusion of oxygen, thus changing the sensing performance of a metal oxide (MOX) gas sensor. In this research, silica and alumina (SiO2/Al2O3) composite membranes were deposited in-situ on Pt-modified ZnO by combining chemical vapor deposition (CVD) and ultrasonic spray pyrolysis (USP) methods Through adjusting the ratio of silicon to aluminum (Si/Al), the composition of membranes, the diffusion rate of oxygen and H2 sensing property under different oxygen concentrations were regulated. With the decrease of the Si/Al ratio, the H2 responses of the sensors increased first and decreased then under high (10,000 ppm) oxygen concentration. While under low (50 ppm) oxygen concentration, the H2 responses of the sensors went down first and rose then. The sensors covered with membranes of high Si/Al ratio exhibited aerobic H2 sensing property. Meanwhile, sensors deposited with membranes of low Si/Al ratio or without membrane showed anaerobic H2 sensing property. This study contributes to further understanding of the influence of oxygen diffusion on MOX sensing properties.