Sensing mechanism of the zirconia-based highly selective NO sensor by using a plate-like Cr_2O_3 sensing electrode

摘要

Plate-like Cr_2O_3 has been proved to be highly selective in sensing of nitric oxide (NO), while the sensing response of irregular shape and cubic-like Cr_2O_3 toward NO was significantly interfered by hydrocarbons (HCs), e.g. C_3H_6. In this paper, sensing mechanism of the plate-like Cr_2O_3 for selective sensing of NO (against HCs) was studied via crystallographic phase analysis, lattice fringes investigation and evaluation of the catalytic activity (gas-phase catalytic activity & electrochemical catalytic activity). The Cr_2O_3 samples with plate-like, irregular shape and cubic-like microstructures have been confirmed to be the same crystallographic phase through XRD measurements, however, significant difference in the lattice fringes of these Cr_2O_3 samples were observed via high-resolution transmission electron microscopy (HRTEM) & selected-area electron diffraction (SAED). The comparison results of catalytic activity for plate-like, irregular shape and cubic-like Cr_2O_3 indicated that the unique selectivity for the plate-like Cr_2O_3 was mainly caused by the electrochemical reaction specifically toward NO, which occurred near the interface between plate-like Cr_2O_3 and zirconia-based electrolyte.