The crystal facet-dependent gas sensing properties of ZnO nanosheets: Experimental and computational study

Herein, we focused on the effects of exposed crystal planes on the gas sensing property of ZnO. For this purpose, we designed and synthesized two porous ZnO nanosheets with different exposed crystal facets (0001) and (101¯0) by a facile hydrothermal routes. The characterization results show that both the porous nanosheets have a near specific surface area about 7.5 m2/g, thickness about 100 nm, diameter about 5 μm and pore size of tens of nanometers. However, their dominating exposed crystal facets are (0001) and (101¯0), respectively. When employed them as sensing materials in gas sensors, porous ZnO nanosheets with dominating exposed (0001) facet exhibit a superior sensitivity than the (101¯0) one. The enhanced gas response is attributed to a large amount of oxygen vacancy defects and unsaturated dangling bonds existing in the ZnO nanosheets with exposed crystal facet (0001), which is favorable for the adsorption of gas molecular on the sensor surface and result in improvement of the gas response. Finally, the calculation of the chemisorption energy of oxygen on ZnO crystal facets also proves the reactive-facet-enhanced gas sensitivity.