Lotus pollen derived 3-dimensional hierarchically porous NiO microspheres for NO2 gas sensing

Hierarchically porous NiO microspheres with interconnected nano-pores were prepared with chemical bath deposition by using lotus pollens as bio-templates. The NiO microspheres thus derived have a specific surface area of 95.58 m2/g and the average pore size is 20.98 nm, such a nanostructure is ideal for gas sensing. To enhance the performances, the NiO microspheres were further decorated with Pd/PdO, and the sensor based on the Pd-decorated NiO microspheres demonstrated a high sensitivity (S = 203), fast response/recovery (73 s/169 s) and excellent selectivity to 1.8 ppm NO2 gas at 250 °C. Compared with the other NO2 gas sensors based on NiO reported in previous works, the sensitivity of the NO2 sensor of this work is the highest and the response/recovery is among the fastest.