In this work, we successfully prepare the octahedral NiO/Zn2SnO4 p-n heterostructure by a simple hydrothermal synthesis and subsequent wet impregnation process. The microscopic morphology characterization results show that the as-prepared composites are uniformly dispersed and have an octahedral structure with a size of 3−5 μm. The gas devices are fabricated and their sensing performances are investigated systematically. The response and selectivity of NiO/Zn2SnO4 composites to acetone have been significantly improved than that of pure Zn2SnO4. Moreover, the response of the sensor to 100 ppb acetone is 1.4 at 300 °C, indicating that the detection limit is less than 100 ppb. The enhancement in sensing properties of composites is largely due to the p-n heterojunction formed by NiO and Zn2SnO4, which causes the transfer of carriers and the catalytic effect of NiO.
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