Recently emerging materials for advancing gas sensor technology have potentialized versatile applications of a sensor in the society of safety, health, environmental protection and much more [1]. In accordance with significant progress of chemical and physical approaches, gas sensing materials are not limited to metal oxide but include various 2D nanostructures such as graphene and metal dichalcogenides, etc. [2, 3]. Of these, the rise of interest on newly discovered 2D transition metal carbides and/or carbonitrides (called MXenes) have recently shown their potential as sensing materials with their intriguing surface chemistry [4]. The first MXene material introducing in chemiresistive sensor is titanium carbide (Ti₃C₂T_x). Gas sensing capabilities of Ti₃C₂T_x MXene to detect various gases were demonstrated with their sensing mechanism [5], and now, further enhancement of its sensing performance is actively studied in many academic domains. Beginning with Ti₃C₂T_x, vast diversity in a combination of constituent elements and ordered structure in MXenes offers future possibilities to find out a new generation of sensing materials with their superior performance.

In this study, 2D V₂CT_x gas sensors were firstly demonstrated in chemiresistive sensing. The sensor device was fabricated with single/few-layer 2D V₂CT_x on polyimide film after the selective etching process. This device measured both polar and non-polar chemical species such as hydrogen and methane at room temperature (23 °C) with an ultra-low limit of detection of 2 ppm and 25 ppm, respectively. 2D V₂CT_x gas sensors showed excellent gas sensing performance in terms of high response toward non-polar gases, which is originated from the surface oxygen functional groups on the surface of V₂CT_x nanoflakes. Compared to the sensing properties of Ti₃C₂T_x MXene [5], 2D V₂CT_x sensor showed higher selectivity and long-term stability. This comparative result suggests that the modification of ordered structure and constituent elements of MXenes play a pivot role in the interaction between analyte and MXenes leading to an extensive change in performance.

References

[1] Barzegar, Maryam, and Bharati Tudu. "Two-dimensional materials for gas sensors: from first discovery to future possibilities." Surface Innovations 6.4–5 (2018): 205-230.
[2] Yang, Shengxue, Chengbao Jiang, and Su-huai Wei. "Gas sensing in 2D materials." Applied Physics Reviews 4.2 (2017): 021304.

[3] Lee, Eunji, et al. "Enhanced Gas-Sensing Performance of GO/TiO2 Composite by Photocatalysis." Sensors 18.10 (2018): 3334.

[4] Xiao, Bo, et al. "MXenes: Reusable materials for NH3 sensor or capturer by controlling the charge injection." Sensors and Actuators B: Chemical 235 (2016): 103-109.
[5] Lee, Eunji, et al. "Room temperature gas sensing of two-dimensional titanium carbide (MXene)." ACS applied materials & interfaces 9.42 (2017): 37184-37190.

Acknowledgement

This research was partially supported by the Korea Institute of Energy Technology Evaluation and Planning (KETEP), grant funded by the Korea Government Ministry of Trade, Industry and Energy (20158520000210), and Agency for Defense Development (ADD) as global cooperative research for high performance and light weight bio-urine based fuel cell (UD160050BD).