Gas-sensing performance of In2O3@MoO3 hollow core-shell nanospheres prepared by a two-step hydrothermal method

Core-shell semiconductor nanostructures can be suitable for high-performance gas sensors due to their unique structural features. In this study, In2O3@MoO3 core-shell hollow spheres were synthesized by a facile two-step solvo-thermal method, followed by post-heat treatment. The synthesis results in 20-nm thick MoO3 shells coated on In2O3 hollow spheres (200-nm diameter). The effects of the morphology and composition on gas sensing performance were systematically investigated by adjusting the molar ratio of In to Mo. The sensing tests suggest that the core-shell structure with the In to Mo molar ratio of 1:1 exhibits the highest sensing response (28.1) towards 100-ppm n-butylamine at the optimized working temperature of 300 °C. This response is two times higher than that of the In2O3 & MoO3 binary mixture (11.1) and five times than that of the pristine In2O3 hollow spheres (4.8). The sensing performance is a result of the unique core-shell structures including both the catalytic reaction mechanism of MoO3 and the co-catalytic properties of the In2O3 hollow spheres. This study may shed light on the design of practical, high-performance amine gas sensors in the future.