Electrochemical and Electric Field Response Properties of Highly Sensitive Electrodes Based on Carbon Fiber With Oxygen and Nitrogen Surface Groups

In this paper, a high-sensitive carbon fiber electrode enriched oxygen and nitrogen groups were prepared using a method combining oxidation and graft modification. The surface compositions were analyzed by means of Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The electrochemical results show that the modified carbon fibers have a better electric double layer performance and a lower capacitive impedance at the lower frequency. The offset potential of the electrode pairs is typically below 1 mV with a drift of less than
$40~\mu \text{V}$
/day. Typical measured noise level is below 2 nV/rt (Hz) at 1 Hz. The modified carbon fiber electrode pairs exhibit a good response to the ac sine signal of amplitude 1 mV and frequency 1 mHz. The sensitivity is increased by 82% and 59%, respectively, in comparison with Ag/AgCl electrode pair. The possible mechanism of the electric field response is discussed by the model of the electric double layer. This carbon fiber electrodes could provide the potential candidate and the theoretical basis for the design of high-sensitivity marine electric field sensor.