Investigation about doping effects of different noble metals for ethanol gas sensors based on mesoporous In2O3.

2021 
Elaborating the sensitization effects of different noble metals on In2O3 has a great significance in providing optimum method to improve ethanol sensing performance. In this study, long-range ordered mesoporous In2O3 has been fabricated through replicating the structure of SBA-15. Different noble metals (Au, Ag, Pt and Pd) with the same doping amount (1 at%) have been introduced by in-situ doping routine. The results of gas sensing investigation indicate that the gas responses towards ethanol can be obviously increased by doping different noble metals. Especially, the best sensing performance towards ethanol detection can be achieved through Pd doping, and the sensors based on Pd doped In2O3 not only possess the highest response (39.0 to 100 ppm ethanol) but also have the shortest response and recovery times at the optimal operation temperature of 250oC. The sensing mechanism of noble metal doped materials can be attributed to the synergetic effect combining "catalysis" and "electronic and chemical sensitization" of noble metal. In particular, the chemical state of noble metal also has great influence on gas sensing mechanism. Detail explanation about the enhancement of gas sensing performance through noble metal doping is presented in gas sensing mechanism part of the manuscript.
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