Role of nickel dopant on gas response and selectivity of electrospun indium oxide nanotubes

Abstract

It has been demonstrated that the incorporation of Ni into metal oxide-based gas sensors often enhances the sensing performance by increasing the catalytic and heterojunction effects. However, it remains unclear how these two effects work either individually or synergistically in gas sensing. Herein, a series of Ni-doped In2O3 nanotubes (NIO NTs) with different doping concentrations were synthesized through a traditional electrospinning technique. The as-prepared NIO NTs were uniform, with length of micron scale, an average diameter of approximately 70 nm, and a tube wall thickness of approximately 10 nm. Following their incorporation into gas sensors, the NIO NTs often showed improved sensing properties (including excellent response and selectivity) for ethanol vapor compared to the pristine In2O3 NTs. Specifically, at 100 ppm ethanol and 220 °C, the response of NIO-7 NTs (7 mol% Ni) was approximately four-fold higher than that of pristine In2O3 NTs (49.74 vs. 13.39). The gas sensing test results indicated that the improved sensing performance was due to the formation of a heterojunction between In2O3 and NiO, as well as to the catalysis effects of Ni3+ ions. Additionally, simulation results indicated that the improved gas selectivity could be due to the Ni doping-induced change in surface adsorption energies of the tested gases.