Design and preparation of hollow NiO sphere- polyaniline composite for NH3 gas sensing at room temperature

The composite of hollow NiO sphere and PANI was designed and synthesized by facile solvothermal process, calcination and in-situ polymerization. The sensor based on hollow NiO sphere-PANI has presented superior sensitivity, stability and selectivity to NH 3 at room temperature. • The solvothermal synthesis was applied to produce bimetal oxide and hollow NiO-CuO metal oxide was obtained. • The sensor based on hollow NiO-PANI composite presented outstanding sensitivity, stability and selectivity to NH 3 at room temperature. • The enhanced sensing performance was ascribed to the hollow structure and the construction of p-p heterojunction. The accurate and rapid sensing of NH 3 at room temperature is a challenging conundrum for daily life and environment protection. In this work, we have explored an intriguing material, hollow NiO sphere composited with polyaniline (labelled as h-NiO-PANI) for NH 3 gas sensing, fabricated by growing PANI on the hollow NiO sphere derived from solvothermal synthesis and calcination. Ni-Cu glycerate is obtained via solvothermal synthesis, which is a universal way to produce uniform glycerate microspheres. During calcination, the hollow sphere is ingeniously designed by taking advantage of the outward adhesion from CuO to the inner core. Polymerization of aniline on the hollow spheres is beneficial for large specific surface area and gas adsorption. Impressively, the sensor based on h-NiO-PANI exhibits favorable response to NH 3 (ΔR/R 0 =43 % for 10 ppm, 149 s in response and 257 s in recovery), which is greatly better than the counterparts (NiO-PANI and PANI). Moreover, the sensor has also shown superb anti-interference against common volatile organic compounds (VOCs), water and humidity, along with the superior repeatability in 5 cycles and long-term stability in a week, manifesting the sensor a promising candidate in daily application. The enhanced gas sensing performance is attributed to the hollow structure and construction of p-p heterojunctions between NiO and PANI.