Improved Hydrogen Gas Sensing Performance of Carbon Nanotube Synthesized Using Microwave Oven

Abstract

Obtaining a high-performance hydrogen (H2) gas sensor based on carbon nanotube (CNT) remains challenging. In this view, two CNT samples such as untreated (R-CNT) and nitric acid (HNO3)-treated (called functionalized or F-CNT in short) were deposited on the SiO2/Si substrate using an electrophoretic deposition technique. The structure, morphology, and electrical characteristics of these samples were evaluated. Fourier transform infrared (FTIR) spectra confirmed the presence of OH groups at the walls of nanotubes after acid treatment. Moreover, it found the current increased from <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$35 \mu \text{A}$ </tex-math></inline-formula> for R-CNT to 11 mA for F-CNT. In addition, both R-CNT and F-CNT were used to fabricate H2 gas sensors. The sensing capacity of the obtained sensors was measured under the H2 gas exposure range of 20 to 300 ppm operated at room temperature (RT), 50 °C, and 75 °C. The H2 gas sensor made of F-CNT showed a much higher response (368%) and shorter response time (15 s) as well as recovery time (72 s) than the one made using R-CNT. It was asserted that the H2 gas sensing performance of the proposed sensor can significantly be improved via the acid treatment or functionalization of CNT.