Selective Detection of CO Using Proton-Conducting Graphene Oxide Membranes with Pt-Doped SnO₂ Electrocatalysts: Mechanistic Study by Operando DRIFTS

To reduce the risk of carbon monoxide (CO) poisoning, there is a strong need for small, compact gas sensors to detect and monitor CO at ppm concentrations. In this study, we focused on detecting CO with electrochemical sensors based on proton-conducting graphene oxide (GO) nanosheets at room temperature. We found that a Ce-doped GO nanosheet membrane fitted with the sensing electrode composed of Pt (10 wt %)-doped SnO 2 nanocrystals exhibits an excellent sensor response to CO at 25 °C. Pt doping of SnO 2 nanocrystals has made it possible to detect CO more selectively than H 2 and ethanol. The CO detection mechanism is analyzed by operando diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), Fourier transform infrared gas cell measurements, and comprehensive density functional theory-based calculations. The results revealed that adsorption of CO occurs predominantly on Pt sites, and the adsorbed CO is anodically oxidized at the interface between the sensing electrode and proton-conducting membrane, generating the selective sensor response. The strong adsorption of CO was realized with Pt (10 wt %)-doped SnO 2 nanocrystals, as revealed by the DRIFTS analysis and temperature-programed desorption technique.