Synthesis of ZnO nanosheets @In2O3 hollow micro-rods heterostructures for enhanced ethanol gas sensing performance

In this paper, the ZnO nanosheets @In2O3 hollow microrods heterostructures were successfully prepared by co-precipitation and annealing methods. It was observed by SEM and TEM that the surface of the In2O3 hollow microrods was uniformly coated with porous ZnO nanosheets, which increased the specific surface area of ZnO@In2O3 composites. The In2O3 hollow microrods functions as electron transport channels and facilitate the transfer of electrons between ZnO nanosheets, consequently elevating the base resistance of sensors. The maximum sensor response of ZnO@In2O3-2 (the molar ratio of ZnO and In2O3 is 5:2) was 269.1 for 100 ppm ethanol at the optimal working temperature of 200 ºC, which is about 30.9 times higher than that of pure ZnO nanosheets (8.7) and 19.1 times higher than that of pure In2O3 (14.1). Additionally, the ZnO@In2O3-2 composites exhibit rapid response-recovery times, excellent selectivity and favorable stability. The improved gas sensing performance of ZnO@In2O3-2 heterostructures were ascribed to its heterogeneous structure building, abundant oxygen vacancies, large specific surface area and internal electric field through characterized by XPS, EPR, and BET.