Abstract
The sensing properties of CO over PtPd/Co3O4 and PtPd/SnO2 catalysts in a micro-thermoelectric gas sensor (micro-TGS) were investigated by in situ diffuse-reflectance infrared Fourier transform spectroscopy (DRIFT) and scanning transmission electron microscopy (STEM), in comparison with other catalysts (AuPtPd/Co3O4, AuPtPd/SnO2, Au/Co3O4, and Au/SnO2) which is reported in our previous works. The catalysts exhibited the following response of voltage signals to CO at 200°C: PtPd/Co3O4>PtPd/SnO2>AuPtPd/SnO2∼AuPtPd/Co3O4>Au/Co3O4>Au/SnO2. From DRIFT spectra, linear and bridge bonds corresponding to Pt–CO and Pd–CO were observed for PtPd/Co3O4 and PtPd/SnO2 catalysts, respectively. In contrast, the Au–CO interaction peak was not clearly observed in the AuPtPd-loaded catalysts. From the STEM observation of the PtPd- and AuPtPd-loaded catalysts, Pt and Pd nanoparticles were well dispersed on catalyst supports. On the other hand, Au nanoparticles formed aggregates with Pt or Pd nanoparticles having a diameter of 10–20nm. Au in the AuPtPd-loaded catalyst was considered to exhibit a low activity for CO oxidation, and the oxidation of CO mainly occurred over Pt and Pd particles. From these results, PtPd/Co3O4 and PtPd/SnO2 are suitable for use as combustion catalysts in micro-TGS for CO detection.
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