Enhancing the Potentiometric H2 Sensing of Pr0.1Ce0.9O2−δ Using Fe2O3 Surface Modification

Abstract

Monitoring the concentration of hydrogen is very important as it is a flammable and explosive gas. Non-Nernstian potentiometric hydrogen sensors hold promising potentials for the sensitive detection of hydrogen. This paper reports the improved H2-sensing performance of a mixed oxide ion-electron conducting (MIEC) Pr0.1Ce0.9O2−δ (PCO) electrode using Fe2O3 surface modification. The Fe2O3-modified PCO exhibited a high response of −184.29 mV to 1000 ppm H2 at 450 °C. The response values exhibited a linear or logarithmic dependence on the H2 concentration for below or above 20 ppm, respectively. A sensitivity of −74.9 mV/decade in the concentration range of 20–1000 ppm was achieved, and the theoretical limit of detection was calculated to be 343 ppb. Moreover, a power-law relationship between the response time and the concentration value was also found. Electrochemical impedance analyses revealed that the excellent H2-sensing performance may be attributed to the large ratio of the electrochemical activity of the hydrogen oxidation reaction (HOR) over the oxygen exchange reaction (OER). In addition, the distribution of relaxation time (DRT) results reveal that the enhanced electrochemical kinetics caused by H2 presence in air is mainly related to acceleration of the electrode surface processes.