Gold-Loaded Tin Dioxide Gas Sensing Materials: Mechanistic Insights and the Role of Gold Dispersion

This work focuses on two aspects of gold loaded tin dioxide gas sensing materials: The influence of the size and dispersion of the gold on the sensing effect and the investigation into the mechanism at the origin of the Unproved gas sensing performance. For this purpose, a set of selected and well-characterized gold loaded tin dioxide materials were examined. The results show that the beneficial effect of gold on the CO sensing performance is observed for nanosized as well as for micron-sized gold entities, i.e., the effect is related to Au itself. Nevertheless, the response is strongly enhanced with increasing gold dispersion. Deeper insights into the mechanism of the sensitization, obtained by state-of-the-art operando spectroscopic techniques, indicated that oxygen is adsorbed on gold and transferred to the tin dioxide surface. There, it is bound as a negatively charged, ionic species, which gives additional sites for the interaction with target gases, i.e., enhances the gas sensing performance. These results strongly support the previously proposed oxygen spillover mechanism for gold-loaded tin dioxide.