Fabrication of a Glow Discharge Plasma-Based Ionization Gas Sensor Using Multiwalled Carbon Nanotubes for Specific Detection of Hydrogen at Parts Per Billion Levels

A new glow discharge plasma-based sensor is fabricated for specific detection of hydrogen (H₂) at parts per billion levels based on gas ionization process under vacuum condition (~0.01 Torr). The system setup consists of a two-electrode system including graphite electrode (diameter: 6.5 mm), modified with arc-synthesized carbon nanostructures as anode and an aluminum disk with 2.4-mm diameter as cathode with interelectrodes distance of 700 ± 10 μm inside a glass chamber. For H₂ detection, ionization current is considered as detection system, during the application of an 853 V direct current potential as a fingerprint breakdown voltage for H₂ ionization to the electrodes. According to the results, the sensor is linear ranging from 40 to 86 ppb. The relative standard deviation of nine replicate analyses during the introduction of ~60 ppb of H₂ is 2.57%. In addition, the detection limit is evaluated to ~3.3 ppb. No interfering effect is observed when introducing at least 1000-fold excess (mass/mass) of foreign species, such as Ar, He, CO₂, CO, C₂H₂, O₂ acetone, and CH₃OH to ~60 ppb of H₂ standard solution. Reliability of the sensor is also evaluated via determination of H₂ in two industrial gas samples.