Biography：Dr. Xiaohong Xia is a professor at Hubei University. She received her PhD degree from the Huazhong Normal University in 2007. She worked at the University of Bolton as a postdoctoral research fellow in 2010-2011, and been promoted to associate professor in 2012 and then to professor in 2017. Her current research interest is design and fabrication of semiconductor materials and devices

Room temperature H₂/CO gas sensors based on TiO₂ homo/hetero junctions

Xiaohong Xia*, Yun Gao, Yuwen Bao, Wei Wei, Huanhuan Zhang, Xiaoyan Zhou, Zhigang Sun, Ya Zhang, Xuefeng Wu, Xuankun Zan, Wen Cheng, Jianhu Liang

Ministry-of-Education Key Laboratory for the Green Preparation and Application of Functional Materials, School of Materials Science & Engineering, Hubei University, Wuhan 430062, China

E-mail: xhxia@hubu.edu.cn 

Safety issues relating to the usage of flammable organic electrolytes of Lithium-ion batteries (LIB) have attracted widespread attention, which is known as battery thermal runaway. Gas detecting is one of the effective methods to monitor the thermal runaway process of LIB. Gases such as H₂, CO, CO₂, HF, HCl, and SO₂ are typically released during the thermal runaway process. H₂ could be detected 435 seconds before the appearance of smoke and 580 seconds before the battery pack caught fire. The warning time for CO is 360 seconds before smoke.[1] To be used in a battery package for H₂ and CO detecting, the sensors should be working at room temperature, small in size, low in power consumption, and easy to integrate into the package. A MEMS hydrogen sensor satisfy the requirement of small size and low power consumption, as well as easy integrating. However, MEMS hydrogen sensor usually use semiconductor oxides as sensing material, which need to work at around 300 ºC [2]. This high working temperature is not safe in the LIB package, room temperature working MEMS hydrogen sensor is urgently needed.

Early detecting of the released gas during charging and discharging of lithium ion battery (LIB) is critical for safety monitoring of the equipment and devices which use LIB as power source. H₂ and CO are typical component of the released gas. The main challenges for detecting H₂/CO in LIB is the low working temperature, small size of the sensor and hypoxic environment. To address these problems, room temperature working H₂/CO sensors were developed, with A-TiO₂/R-TiO₂ homojunction and CuO/TiO₂ heterojunction materials. The sensors have the advantages of low power consumption, easy integration, and excellent sensing performance. The optimized A-TiO₂/R-TiO₂ homojunction H₂ sensor achieves an excellent sensing performance of S=1.21 and fast response/recovery times of about 42s/30s when exposed to 1 ppm H₂. The CuO/TiO₂ sample with the best performance has a response value of 10.8 to 200 ppm CO at room temperature. The construction of the heterojunction promoted the CO response and suppressed the H₂ response, thus improved the selectivity of CO to H₂. The working mechanism of the sensors were analyzed according to the characterization of the sensors.

We have successfully fabricated room temperature working H₂ and CO sensors, which could be utilized in lithium ion battery for early warning of thermal runaway. Distinctive detection of H₂ and CO were realized by constructing TiO₂ based homo/hetero junctions. Surface adsorption and band structure optimization of the junction are the key parameters for gas sensing property improving.

References

[1] Y. Jin, Z. Zheng, D. Wei et al, Joule, 4, 1714 (2020).

[2] X. Wang, X. Meng, W. Gao, Sensors and Actuators B: Chemical 387 (2023).

[3] Z. Wang, M. Deng, X. Xia, Y. Gao, G. Shao, Energy & Environmental Materials, 1(3), 174-178 (2018).

[4] Z. Sun, L. Huang, Y. Zhang, et al Sensors and Actuators B, 134675 (2023).

[5] X. Li, Z. Sun, Y. Bao, X. Xia, et al., Sensors and Actuators B: Chemical, 350, 130869 (2022).

[6] X. Zhou, T. Tao, X. Xia, et al., ACS Applied Materials & Interfaces, 13(21), 25472-25482 (2021).

[7] H. Zhang, W. Wei, et al. Sensors and Actuators B: Chemical, 380: 133321 (2023).

[8] W. Wei, H. Zhang, T. Tao, et al., Energy & Environmental Materials, 6(3) e12570 (2023)