Mechanochemical approach for fabrication of a nano-structured NiO-sensing electrode used in a zirconia-based NO2 sensor

Highly uniform NiO nano-particles with a crystallite size of about 3 nm were obtained by room-temperature ball-milling of the parent Ni(OH)2, which was derived using a sol–gel method. The obtained nano-structured NiO precursor was then utilized for the fabrication of NiO-sensing electrodes (SEs), which were further examined in the mixed-potential-type YSZ-based planar NO2 sensor. The obtained results revealed the attractive advantages for the application of mechanochemical approach in regard to achieve high NO2 sensitivity, NO2 selectivity and reproducibility. All of the evaluated sensors attached with the nano-structured NiO-SEs, regardless of its sintering temperature, were found to exhibit high NO2 sensitivity at 800 °C under the wet condition (5 vol.% water vapor). In addition to high NO2 sensitivity, the sensor attached with 1100 °C-sintered NiO-SE showed highly selective properties towards NO2. The observed improvement in NO2-sensing characteristics as well as the attainment of highly reproducible behavior for different sensor devices is discussed based on morphological and electrochemical observations of the studied sensors

Potentiometric YSZ-based sensor using NiO sensing electrode aiming at detection of volatile organic compounds (VOCs) in air environment

The potentiometric yttria-stabilized zirconia (YSZ)-based sensors using each of various oxide sensing-electrodes (SEs) were fabricated and examined for detection of toluene (C7H8) in several tens ppb level. As a result, the sensor using NiO-SE was found to exhibit relatively high sensitivity and selectivity to toluene at 450 °C under the wet condition (1.35 vol.% H2O). The present sensor could respond well to toluene in the concentration range of 10–150 ppb. The response transients to 50 ppb toluene were stable and repeatable, accompanying with the response/recovery time acceptable for an actual environmental monitoring. In addition, the toluene sensitivity was hardly affected by the interference of the other co-existing gases examined. Keywords: Gas sensor, Environmental monitoring, VOCs, YSZ, Toluene, Mixed potentia