Sensing Properties and Mechanism of Gas Sensors Based on Room-Temperature Solution Processed NiO-Ni<sub>v</sub> Nanoparticles
Zhengwang Cheng, Ruo-Yue Fan, Jiajun Liao, Gang Yuan, Xiaoqiang Wu, Wenbo Pi, Wei Zou, Xinguo Ma, Mei Wang
Abstract
Developing high-performance, energy-efficient, and cost-saving metal oxide-based gas sensors for NO 2 detection at room temperature is of immense importance. In this work, nonstoichiometric NiO-Ni v was prepared by a low-cost chemical coprecipitation method and then deposited as a sensing film for NO 2 detection at RT without further postannealing. The NiO-Ni v sensor showed a maximal response value of 12.42 toward 20 ppm of NO 2 gas, 7.8 times higher than that of the pure NiO. Moreover, it exhibited quite high selectivity and stability to NO 2 gas, with its properties almost maintained even after 1 month. This exceptional sensing performance might be attributed to the unique surface morphology and abundant nickel vacancies that induced high activity in NiO-Ni v . To investigate the sensing mechanism, the adsorption energy and charge density difference were calculated by first-principles calculations based on the density functional theory. It demonstrated that NiO with nickel vacancy can adsorb NO 2 more easily and that there was more charge transfer between NiO-Ni v and NO 2 molecules compared to that of pure NiO. Furthermore, a potential gas-sensing mechanism involving nickel vacancies was proposed to elucidate the origin of the enhanced sensing property. The improved strategy can be broadly applied to p-type semiconductor-based gas sensors.