Estimation of adsorption energy for water molecules on a multi-walled carbon nanotube thin film by measuring electric resistance

Takuya Kokabu,Yukihiko Matsumura,Shuhei Inoue

doi:10.1063/1.4967784

Takuya Kokabu, Yukihiko Matsumura + Show 1 more

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https://doi.org/10.1063/1.4967784

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Journal: AIP Advances	Publication Date: Nov 1, 2016
Citations: 14	License type: cc-by

Affiliation: Hiroshima University

Abstract

Gas sensors based on carbon nanotube (CNT) films have attracted attention owing to their low power consumption. For further development of these sensors, we need to understand the surface interaction of the films with gas molecules. In our previous research, we investigated the influence of water molecules on the electrical conductance of multi-walled CNT films and explained this phenomenon using a two-layer adsorption model. This work motivated us to measure the adsorption energy of CNT-H2O. In this study, we focused on the first-layer adsorption and investigated the sheet resistance to water vapor pressure at various temperatures using the transmission line method (TLM). The results were fitted to Langmuir adsorption model and the adsorption equilibrium constant was determined. The temperature dependence of the sheet resistance followed a model of fluctuation induced tunneling (FIT), in which the energy barrier at the CNT junction is regarded as the main factor influencing the electrical conductance of the CNT film. The sheet resistance and equilibrium constant decreased as temperature increased. This result was consistent with the adsorption phenomenon. Finally, the adsorption energy was determined to be 0.22–0.31 eV, which is larger than the previously calculated value. It was also reported that the adsorption energy of the gas molecules in the interstitial site between two carbon nanotubes was larger than that on the CNT surface. These results indicate that the CNT junction plays a key role in the detection of gas molecules.

Highlights

ARTICLES YOU MAY BE INTERESTED INTakuya Kokabu,[1] Shuhei Inoue,2,a and Yukihiko Matsumura2 1Department of Mechanical Science and Engineering, Hiroshima University, 1-4-1 Kagamiyama, 739-8527 Higashi-Hiroshima, Japan 2Division of Energy and Environmental Engineering, Hiroshima University, 1-4-1 Kagamiyama, 739-8527 Higashi-Hiroshima, Japan (Received 3 October 2016; accepted 31 October 2016; published online 8 November 2016)
Since Collins et al.[1] and Kong et al.[2] demonstrated a resistive gas sensor for O2, NO2, and NH3 using isolated carbon nanotubes (CNTs) or CNT bundles, CNTs have gained attention for use as next-generation gas sensors because they allow for room temperature operation, as opposed to the currently used semiconducting gas sensors
In our previous study,[26] we investigated the influence of water molecule coverage on the electrical conductance of a multiwalled carbon nanotube (MWCNT) film, in order to understand the surface interaction

Summary

ARTICLES YOU MAY BE INTERESTED IN

Takuya Kokabu,[1] Shuhei Inoue,2,a and Yukihiko Matsumura2 1Department of Mechanical Science and Engineering, Hiroshima University, 1-4-1 Kagamiyama, 739-8527 Higashi-Hiroshima, Japan 2Division of Energy and Environmental Engineering, Hiroshima University, 1-4-1 Kagamiyama, 739-8527 Higashi-Hiroshima, Japan (Received 3 October 2016; accepted 31 October 2016; published online 8 November 2016)

INTRODUCTION

RESULTS AND DISCUSSION

Smax n N

CONCLUSION