Sustainable NO removal and its sensitive monitoring at room temperature by electrogenerated Ni (I) electron mediator

Abstract

Online monitoring of gas pollutants in the gas phase at room temperature using an electrochemical macro gas flow sensor is challenging and important for the pollutant treatment process. In this work, for the first time, we tried to explore the homogeneous and heterogeneous application of Ni(II) (CN)₄^2- in the KOH environment for the removal and monitoring of toxic nitric oxide gas. The homogeneous electrogenerated Ni(I) (CN)₄^3- was effectively removing the toxic nitric oxide gas by electro scrubbing method and the novel Ni(II) (CN)₄^2- and KOH modified electrode used for heterogeneous sensor application with high sensitivity, and reliability toward Nitric oxide gas. The sensor showed enhanced gas diffusion and high sensitivity. Scanning electron microscopy and X-ray diffraction confirmed the modification of the carbon felt electrode. In a high concentrated KOH environment, the active mediator stabilized the sensor for a long time compared to the neutral environment. The Ni(II) (CN)₄^2- fabricated carbon felt was used to monitor the concentration of nitric oxide gas pollutant; the calculated sensitivity was approximately -0.33 mA ppm^-1 cm^-2. The current increased linearly with increasing nitric oxide concentration up to 12 ppm and was validated by online gas chromatography. The developed electrochemical gas flow sensor successfully monitored the unremoved nitric oxide gas at the exit from the MER electro-scrubbing process; the concentration was calculated using a calibration plot.

Keywords: MER electro-Scrubbing process; Nitric oxide gas sensor; Nitric oxide removal; Online gas flow sensor; Room temperature gas sensor.