Enhanced Sensitivity of Hydrogenated Α-Fe 2 O 3 Nanoplates Having {001} Facets and the Gas Sensing Mechanism

Hexagonal α-Fe 2 O 3 nanoplates exposing {001} crystal planes have been synthesized by using ethanol as the control agent of crystal facets. The as-synthesized nanoplates exhibit higher responses to ethanol, methanol and triethylamine than commercial powders, and the responses can be further increased by hydrogenation. The enhancement of sensitivity is attributed to an increase in density of 3-coordinated Fe (Fe 3 c ) atoms at the exposed (001) crystal plane after hydrogenating. The unsaturated Fe 3 c atoms at the Fe-terminated polar (001) surface are evidenced to serve as an active site for gas sensing, and a gas sensing mechanism at atomic scale is presented. On the (001) surface, the 3-coordinated Fe atoms adsorb oxygen and catalyzes the reaction of the adsorb oxygen with test gases. The adsorption and desorption of oxygen leads to a change in resistance of the α-Fe 2 O 3 nanoplate sensor. This mechanism is instructive for the comprehending of gas sensing reactions, and the design of highly sensitivity gas sensing materials and devices.