Pd/ZnO nanorods based sensor for highly selective detection of extremely low concentration hydrogen

We report highly hydrogen selective Pd contacted ZnO nanorods based sensor detecting low concentration even at low operating temperature of 50 °C. The sensor performance was investigated for various gases such as H₂, CH₄, H₂S and CO₂ at different operating temperatures from 50 °C to 175 °C for various gas concentrations ranging from 7 ppm to 10,000 ppm (1%). The sensor is highly efficient as it detects hydrogen even at low concentration of ~7 ppm and at operating temperature of 50 °C. The sensor's minimum limit of detection and relative response at 175 °C were found 7 ppm with ~38.7% for H₂, 110 ppm with ~6.08% for CH₄, 500 ppm with ~10.06% for H₂S and 1% with ~11.87% for CO₂. Here, Pd exhibits dual characteristics as metal contact and excellent catalyst to hydrogen molecules. The activation energy was calculated for all the gases and found lowest ~3.658 kJ/mol for H₂. Low activation energy accelerates desorption reactions and enhances the sensor's performance.