Investigation of gas-sensitivity of sensor structures to hydrogen in a wide range of temperature, concentration and humidity of gas medium

Abstract

Response to H2 of seven sensor structures of SnO2 with various catalytic additives, made by thick-film technology, was investigated in a dry gas medium at a concentration of 200 ppm H2 in a temperature range of 100–600 °C. Concentration dependence of six sensors (pure SnO2 and doped with five catalytic additives: 3% Pd, 3% La2O3, 1% Pt + 3% Pd, 1% Sb2O5 + 3% La2O3 and 3% Pd with a support layer from Al2O3) was investigated in a range of 1–19,700 ppm H2 of different relative humidity (RH) in a range of 0–100% RH at two operating temperatures. The resistance and response of the sensors weakly depended on the humidity of the gas medium at RH ≥ 0 or 10%. Arithmetic mean values of response and resistance in the range of 0 (10)–100% RH were approximated by linear functions of log(Sma − 1) = B + n log C and log Rma = A + k log C, respectively. Based on the comparative analysis of experimental data (response to H2, reproducibility of indications, influence of humidity on the resistance and response, response threshold and a resistance drift in pure air), the best for H2 detection were the two sensor structures of pure SnO2 and SnO2 + 3% La2O3, working at temperatures 500 °C and 450 °C, respectively. Formulas for resistance and response of these sensors were presented, which allowed estimation of H2 concentration in air based on the measured parameters. Reproducibility of indications in the range of 1–19,700 ppm H2 was within 4–10%. The response threshold was 0.08 ± 0.006 ppm H2 in the mentioned range of humidity at the response equal to 1.1. The interpretation was given for the mechanism of interaction of H2 with the catalytic surface of semiconductive sensors. The present sensors can be recommended as the primary transducer of H2 concentration in air for the gas control devices.