Analysis of factors affecting response for mixed potential gas sensors

Electrochemical Response of Mixed Conducting Perovskite Enables Low-Cost High-Efficiency Hydrogen Sensing

“…Strikingly, the response is positive (i.e., potential increases) for reducing analyte gases, including H 2 , CO, NH 3 , CH 4 , C 3 H 8 , and C 7 H 8 , and negative (potential decreases) for the oxidizing gas, NO 2 . The response sign of SFT50 is exactly the opposite of that expected by theories 17,40 and observed in experiments for conventional materials, 8,12 suggesting a new sensing mechanism. The response increases with decreasing temperature and with increasing H 2 concentration (Figures 3b and S4), yielding 60 mV for 500 ppm of H 2 at 500 °C.…”

“…40,41 A large R p, OER /R p, HOR ratio favors the mixed potential H 2 response, and vice versa. 17,40 For SFT50, R p, OER is rather small at 600 °C, typical for MIECs with high OER activities, whereas R p, HOR is much larger (Figure 6a); the R p, OER /R p, HOR ratio (∼1/55 for 500 ppm of H 2 ) is much smaller than that of regular materials 40 and expected to yield an insignificant mixed potential response. Under sensing conditions, the electrical resistance of the p-type semiconducting SFT50 increases in H 2 (Figure S10), indicative of increased electron concentration due to the surface chemical reaction (Figure S11).…”

“…First, it has no or even an adverse contribution to the sensor response, unfavorable for the sensing and material utilization efficiency. 17,18 Second, Pt is costly and scarce, increasing the sensor cost. Third, it often suffers from instability due to impurity poisoning and high temperature sintering.…”

“…Conventional electrode materials, including metals, simple oxides, complex oxides, or their composites, mostly exhibit the same response polarity, i.e., negative (positive) response to reducing (oxidizing) gases, which is usually ascribed to mixed potential and conductivity change. 8,12,17,22 When two of these materials are paired up in a planar-type sensor, which features simplicity and miniaturizability, their responses (partly) cancel out, degrading the sensor performance. 17,23 Although connecting sensors in series can amplify the sensor signals, it leads to a complex, bulky, and costly device.…”

“…8,12,17,22 When two of these materials are paired up in a planar-type sensor, which features simplicity and miniaturizability, their responses (partly) cancel out, degrading the sensor performance. 17,23 Although connecting sensors in series can amplify the sensor signals, it leads to a complex, bulky, and costly device. 12,24 To overcome these problems, exploring materials with unconventional response polarity while simultaneously having a high gas sensitivity, which can maximize the sensor response, is vital yet challenging.…”