Synthesis of NiO hollow nanospheres via Kirkendall effect and their enhanced gas sensing performance

Based on the Kirkendall effect, a facile calcination method was used to synthesize p-type semiconductor NiO hollow nanoparticles. The composition, structure, morphology and specific surface of NiO hollow nanospheres were characterized by means of XRD, TEM and BET and their gas sensing properties were studied. It was found that the hollow NiO nanospheres have certain gas sensing properties to methanol, ethanol and n-butanol. The results showed that NiO-4 prepared at 500 degrees C for 4 h had excellent sensitivity and selectivity to n-butanol gas at the optimized operating temperature of 240 degrees C (1000 ppm of n-butanol, R-g/R-a = 9.0). The sensing mechanism of responses is proposed considering the unique material structure. Thin and permeable shell is the key factor to improve the n-butanol reaction, which is beneficial to complete electron consumption and effective gas diffusion. This strategy offers a facile way for the design of hollow nano-materials and may also extend to prepare other metal oxides such as CoO, SnO2 or Bi2O3 hollow nanostructures.