Room-Temperature Hydrogen-Sensing Capabilities of Pt-SnO(2) and Pt-ZnO Composite Nanoceramics Occur via Two Different Mechanisms

Impressive room-temperature gas-sensing capabilities have been reported for nanomaterials of many metal oxides, including SnO(2), ZnO, TiO(2), WO(3), and Fe(2)O(3), while little attention has been paid to the intrinsic difference among them. Pt-SnO(2) and Pt-ZnO composite nanoceramics have been prepared through convenient pressing and sintering. The former shows strong and stable responses to hydrogen in 20% O(2)-N(2) (synthetic air) at room temperature, while the responses to hydrogen in N(2) cannot be stabilized in limited times; the latter shows strong and stable responses to hydrogen in N(2), while the responses to hydrogen in synthetic air are greatly depressed. Further analyses reveal that for Pt-ZnO, the responses result from the reaction between hydrogen and oxygen chemisorbed on ZnO; while for Pt-SnO(2), the responses result from two reactions of hydrogen, one is that with oxygen chemisorbed on SnO(2) and the other is hydrogen chemisorption on SnO(2). These results reveal two different room-temperature hydrogen-sensing mechanisms among MOXs, which results in highly contrasting room-temperature hydrogen-sensing capabilities attractive for sensing hydrogen in oxygen-contained and oxygen-free environments, separately.