Crystal facets-controlled NiO/SnO2 p-n heterostructures with engineered surface and interface towards triethylamine sensing

Crystal facets engineering is an effective means to improve the gas sensing performance of metal oxides and has become a research hotspot recently. However, research on crystal facets engineering are mainly focused on single metal oxides semiconductor, there are still very limited report about the crystal facets engineering on the semiconductor p-n heterostructures. In the present study, NiO/SnO2 p-n heterostructures were constructed by wrapping SnO2 nanocrystals exposing different crystal facets with 2D porous NiO nanosheets networks. It was found that the heterostructures with coexisted SnO2 {221} and {110} crystal facets displayed a significantly improved triethylamine sensing performance with a high response value of 78.5 towards 100 ppm triethylamine, together with ultrafast response characteristics (< 3 s), excellent stability and selectivity. The related mechanism was described through theoretical calculation. On the one hand, {221} crystal facets had higher activity and provided more active sites for the surface adsorption of triethylamine. On the other hand, the strong electron interaction between {110} facets and NiO was favorable for efficient electron transfer in interface, which further enhanced the gas sensing activity of heterostructures. This study provides a new idea for improving the gas sensing performance of metal oxide heterostructures through collaborative optimization of surface and interface.