Abstract
Sensing reaction mechanism is crucial for enhancing the sensing performance of semiconductor-based sensing materials. Here we show a new strategy to enhancing sensing performance of SnO2 nanocrystals by increasing the density of unsaturated Sn atoms with dangling bonds at the SnO2 surface through hydrogenation. A concept of the surface unsaturated Sn atoms serving as active sites for the sensing reaction is proposed, and the sensing mechanism is described in detail at atomic and molecule level for the first time. Sensing properties of other metal oxide sensors and catalytic activity of other catalysts may be improved by using the hydrogenation strategy. The concept of the surface unsaturated metal atoms serving as active sites may be very useful for understanding the sensing and catalytic reaction mechanisms and designing advanced sensing sensors, catalysts and photoelectronic devices.
Highlights
IntroductionAs an important n-type metal-oxide semiconductor with a band gap of 3.6 eV at 300 K1, tin dioxide (SnO2) is well known for its numerous potential applications in field emission[2,3,4], lithium ion batteries[5,6,7], photocatalysis[8, 9], dye-sensitizd solar cells[10, 11], perovskite solar cells[12,13,14,15], supercapacitors[16, 17], light emitting devices[18] and so on
Scanning electron microscope (SEM) image shown in Fig. 1b indicated that the SnO2 samples without hydrogenation consists of nanocrystals with irregular morphology and the sizes of 50–500 nm
The three kinds of hydrogenated samples were characterized with FESEM and X-ray diffraction (XRD), and the results are shown in Supporting Information Fig. 1
Summary
As an important n-type metal-oxide semiconductor with a band gap of 3.6 eV at 300 K1, tin dioxide (SnO2) is well known for its numerous potential applications in field emission[2,3,4], lithium ion batteries[5,6,7], photocatalysis[8, 9], dye-sensitizd solar cells[10, 11], perovskite solar cells[12,13,14,15], supercapacitors[16, 17], light emitting devices[18] and so on. The variations of the resistances are brought about by the oxidation-reduction reaction of the adsorbed oxygen with the test gas taking place on the metal-oxide surface[45, 46] For this reason, the sensing behaviors of metal oxides should be very sensitive to the surface adsorption oxygen ability of the sensing materials. The adsorption oxygen ability may be enhanced by increasing density of the unsaturated metallic atoms with dangling bonds on the surface of metal-oxide sensors through hydrogenation. Such a strategy for increasing sensing properties has never been reported up to now. The excellent gas-sensing performance arises from the increased density of the unsaturated Sn atoms with dangling bonds through hydrogenation, a concept of the unsaturated Sn atom serving as an active site for the sensing reaction is proposed, and a new sensing reaction mechanism is described in detail
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