Finely dispersed and highly toluene sensitive NiO/NiGa2O4 heterostructures prepared from layered double hydroxides precursors

Fabrication of heterojunctioned gas sensing materials is regarded as one of the most efficient ways to improve sensor performance. Herein, finely dispersed NiO/NiGa2O4 heterojunction-based material is synthesized successfully by calcining the atomically mixed Ni-Ga precursors of layered double hydroxides (LDH). The optimized atomic ratio of Ni/Ga is 2.5 and the annealing temperature in H2 is 300 °C, and the obtained material shows a high response of 10.54 to 5 ppm toluene working at a low temperature of 200 °C. As a comparison, the co-precipitation method prepared analogue shows relatively lower response with the value of 8.5 at a higher working temperature of 250 °C, showing the advantage of this LDH prepared material. Moreover, it shows also high selectivity over other interfering gases such as chlorobenzene, acetone, humidity, NH3 and SO2, and long stability over one month measurements. X-ray diffraction, X-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy show the efficient NiO/NiGa2O4 heterojunctions fabricated from LDH precursors, which are further enhanced in H2 to induce oxygen vacancy and Schottky barrier of Ni-NiO/NiGa2O4, promising for high performance gas sensors.