Moisture-induced reversible material transition behavior of Nickel (II) bromide for low humidity detection

• Published in: Sensors and actuators. A. Physical. 2021-11, Vol.331, p.112911, Article 112911
• Main Authors: Yin, Mengqi, Hu, Jinyong, Huang, Mingpeng, Chen, Pei, Zhang, Yong
• Format: Article
• Language: English
• Subjects: Absorption; Adsorption; Discoloration; Humidity; Low humidity detection; Manufacturing; Material transition; Moisture; Nickel; Nickel (II) bromide; Relative humidity; Response time; Reversible bulk absorption behavior; Semiconductors; Sensitivity; Sensors; Water chemistry
• ISSN: 0924-4247; 1873-3069
• DOI: 10.1016/j.sna.2021.112911

[Display omitted] •Moisture-induced discoloration material NiBr2 is developed for low humidity detection based on its reversible material transition behavior.•The NiBr2 humidity sensor exhibits good sensitivity in the low RH range of 7 %–24 %, with impedance variations of nearly 5 orders of magnitude.•The NiBr2 humidity sensor manifests rapid response characteristic with 2 s of response time in low humidity detection. Low humidity monitoring has been attached to adequate attention in a wide range of industrial fields, such as medical device hermetic packaging, semiconductor manufacturing and transformer manufacturing. However, it remains challenging to detect slight moisture change in low-humidity environment for conventional ionic-type humidity sensors. Herein, Nickel (II) bromide (NiBr2) is explored to be of a reversible moisture-induced discoloration behavior and highly sensitive to moisture in low humidity environment. NiBr2 humidity sensor delivers a tremendous impedance change nearly to 5 orders of magnitude in the low relative humidity (RH) ranging from 7 % to 24 % and the response time is only about 2 s when RH increases from 11 % to 33 %. The excellent performance for low-humidity detection can be mainly attributed to the reversible bulk absorption behavior to water molecules that lead to a reversible material transition between NiBr2 and NiBr2⋅6H2O. Meanwhile, the sensitivity of the sensor toward the range of 7 %–24 % RH exhibits nearly 5 orders of magnitude enhancement than that in medium-high humidity range of 26 %–95 % RH, which indicates that the sensitivity of the sensor to water molecules caused by the bulk absorption behavior is better than that dominated by the surface adsorption behavior. The results demonstrate that the bulk absorption behavior-mediated reversible material transition provide efficient guidance to realize low-humidity detection.