2D Molybdenum Carbide MXenes for Enhanced Selective Detection of Humidity in Air.
basic_science · Level V
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- Record sourced from PubMed, PMID 34601739.
- Also identified by DOI 10.1002/adma.202104878 and PMC identifier 11468926.
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Abstract
2D transition metal carbides and nitrides (MXenes) open up novel opportunities in gas sensing with high sensitivity at room temperature. Herein, 2D Mo<sub>2</sub> CT<sub>x</sub> flakes with high aspect ratio are successfully synthesized. The chemiresistive effect in a sub-µm MXene multilayer for different organic vapors and humidity at 10<sup>1</sup> -10<sup>4</sup> ppm in dry air is studied. Reasonably, the low-noise resistance signal allows the detection of H<sub>2</sub> O down to 10 ppm. Moreover, humidity suppresses the response of Mo<sub>2</sub> CT<sub>x</sub> to organic analytes due to the blocking of adsorption active sites. By measuring the impedance of MXene layers as a function of ac frequency in the 10<sup>-2</sup> -10<sup>6</sup> Hz range, it is shown that operation principle of the sensor is dominated by resistance change rather than capacitance variations. The sensor transfer function allows to conclude that the Mo<sub>2</sub> CT<sub>x</sub> chemiresistance is mainly originating from electron transport through interflake potential barriers with heights up to 0.2 eV. Density functional theory calculations, elucidating the Mo<sub>2</sub> C surface interaction with organic analytes and H<sub>2</sub> O, explain the experimental data as an energy shift of the density of states under the analyte's adsorption which induces increasing electrical resistance.