Methane sensor based on nanocomposite of palladium/multi-walled carbon nanotubes grafted with 1,6-hexanediamine

Palladium nanoparticles (PdNPs) were electrolessly deposited on 1,6-hexanediamine grafted multi-walled carbon nanotubes (MWCNTs) to form nanocomposite which was then characterized by scanning electron microscopy, proton nuclear magnetic resonance spectroscopy, and infrared spectroscopy. First, the electrocatalytic activity of MWCNT/PdNPs for methane (CH4) on a gold electrode in 0.50 M H2SO4 was studied by cyclic voltammetry and the results demonstrated that MWCNT/PdNPs could be employed to oxidize CH4. A simple CH4 sensor was then fabricated by depositing the MWCNT/PdNPs nanocomposite onto an indium tin oxide substrate. The effects of carrier gas, amount of nanocomposite and temperature on the response of the sensor were investigated in detail. The sensor exhibits good sensitivity and selectivity to CH4 in dry air at ambient conditions. It showed linear response to CH4 at 0–16% v/v with a detection limit of 0.167% v/v (signal/noise = 3). The response and recovery times were less than 35 and 12 s, respectively. Common gases such as N2, CO and CO2 showed no interference but H2 and NH3 displayed slight interference to the sensor.