Selective hydrogen sensing properties of surface functionalized tin oxide

A simple way of controlling the selectivity of tin oxide based hydrogen sensors by surface functionalization is demonstrated by introducing some misfit regions on tin oxide surface using covalent attachment of Ru, Pd and Ag species. The sensitivity and the selectivity of tin oxide is found to be dramatically enhanced in comparison with pure tin oxide. In addition, synergistic sensitivity effects are observed by simultaneously introducing several noble metal species on the surface of tin oxide; whereby the operating temperature for maximum sensitivity towards hydrogen is found to be drastically reduced. For example, pure tin oxide and surface ruthenated tin oxide shows highest sensitivity (8 and 120, respectively) towards hydrogen at 300 degrees C, while tin oxide functionalized with Ru/Pd and Ru/Pd/Ag shows higher sensitivity (1350 and 360, respectively) at significantly lower temperatures (250 and 150 degrees C, respectively). The amount and distribution of these heterospecies on the surface (affecting the surface electron states of tin oxide) are the most important parameters to be controlled to obtain optimum:sensitivity and selectivity as a function of operating temperature. (C) 1999 Elsevier Science S.A. All rights reserved.