Hydrazine Sensor for Quantitative Determination of High Hydrazine Concentrations for Direct Hydrazine Fuel Cell Vehicle Applications

Abstract

With the discovery of hydrazine as an alternative to hydrogen fuel for the development of fuel cell electric vehicles (FCEV), the need for a hydrazine sensor for the quantitative determination of hydrazine aroused. In contrast to the common hydrazine electrochemical sensors whose main parameters are the low detection and quantification limits, the new electrochemical sensor should satisfy one main requirement: a linear response at high hydrazine concentrations (2-4 M hydrazine). In this study, three types of catalysts were tested for hydrazine oxidation and its electrochemical quantitative determination: Ni0.87Zn0.13, Ni0.95La0.05 and Ni0.85La0.15. Layer-by-layer composites based on the utilization of Ni1-xLax catalyst and diffusion control layer (DCL) were successfully explored in the development of the hydrazine sensor. Ni1-xLax-DCL composites produced a linear response for hydrazine concentrations within 2-4 M, with the highest sensitivity observed from bilayer Ni0.95La0.05-DCL electrodes (13.2 μA M−1 N2H4 or 53.3 μA/M.cm2 N2H4). An alternative approach for the development of a FCEV-hydrazine sensor was also demonstrated. A flow-through sensor with Ni0.95La0.05-RVC (reticulated vitreous carbon) electrode, operating in a constant flow of 1.2 mL/min was designed. The sensor showed current/hydrazine concentration linear dependence in the range 0.05–5 M hydrazine with a correlation coefficient of 0.9999. The sensitivity of the sensor was 31.696 mA/M·g with a limit of detection and a limit of quantitation 0.14 M and 0.72 M, respectively. The uncertainty of the hydrazine concentration was determined to be 4.68% at the middle of the calibration curve.