Selective hydrogen sensing properties of surface functionalized tin oxide

A simple way of controlling the selectivity of tin oxide based hydrogen sen sors by surface functionalization is demonstrated by introducing some misfi t regions on tin oxide surface using covalent attachment of Ru, Pd and Ag s pecies. The sensitivity and the selectivity of tin oxide is found to be dra matically enhanced in comparison with pure tin oxide. In addition, synergis tic sensitivity effects are observed by simultaneously introducing several noble metal species on the surface of tin oxide; whereby the operating temp erature for maximum sensitivity towards hydrogen is found to be drastically reduced. For example, pure tin oxide and surface ruthenated tin oxide show s highest sensitivity (8 and 120, respectively) towards hydrogen at 300 deg rees C, while tin oxide functionalized with Ru/Pd and Ru/Pd/Ag shows higher sensitivity (1350 and 360, respectively) at significantly lower temperatur es (250 and 150 degrees C, respectively). The amount and distribution of th ese heterospecies on the surface (affecting the surface electron states of tin oxide) are the most important parameters to be controlled to obtain opt imum:sensitivity and selectivity as a function of operating temperature. (C ) 1999 Elsevier Science S.A. All rights reserved.