Ocean electric field detection technology is in the ascendant. Traditional Ag/AgCl electrodes are costly and require stringent storage and transportation conditions. And carbon fiber electrodes are susceptible to environmental changes that affect signal response. To address these inherent challenges in practical applications, this study prepares ocean electric field electrodes based on carbon paper. Through electrochemical modification to adjust the number and proportion of oxygen-containing functional groups, we improve the electric field response performance of carbon paper electrode. Experimental findings reveal that electrochemical oxidation (EO)/reduction (ER) introduces a large number of oxygen-containing functional groups onto the electrode surface, altering the surface functional groups and improving surface polarity and hydrophilicity. As the proportion of electrochemical oxidation time gradually increases, EO8 exhibits superior distribution ratios and uniformity of oxygen-containing functional groups. Electrochemical test results indicate that EO8 has a specific capacitance of 1.678 F/g. At 0.01 Hz, the electrochemical impedance of EO8 is 2 117.60 Ω·cm², with the charge transfer resistance of 1 709.60 Ω·cm². These results demonstrate the significant improvement in electrochemical performance of EO8. Electric field response tests show that the potential drift of the EO8 paired electrodes is only 2.12 mV/d, with electrode self-noise reduces to 14 nV/rt Hz@1 Hz. Moreover, the EO8 paired electrodes can effectively respond to low-frequency weak electric field signals of 10 mV and 10 mHz. Compared to blank carbon paper electrodes, the sensitivity and accuracy of modified electrodes are significantly enhanced. Thus, carbon paper becomes promising candidate materials for ocean electric field electrodes.

Carbon fiber electric field electrodes have the advantages of low cost, good chemical stability, and tunable performance, which can be used to develop high-performance ocean electric field sensors. In this paper, surface modification of polyacrylonitrile based carbon fiber was carried out by in-situ electrochemical polymerization of aniline by using ammonium bicarbonate weakly basic solution as electrolyte to fabricate marine composite electrode, and its electrochemical and electric field response performance were studied respectively. The results showed that reduced polyaniline formed on the surface of carbon fiber, in which it appeared characteristic redox peaks. The AC impedance spectrum showed that the modified electrode surface equivalent circuit increased the film capacitance and film resistance, and the electric field response changed from pure capacitance coupling to a hybrid mechanism of capacitance and resistance. It was beneficial to the response of low frequency and low intensity signals. In the electric field performance test, the electric potential drift of the modified electrode pair was as low as 0.66 mV/d, and it induced well to low frequency and low intensity electric field signal at 10 mV, 10 mHz, in which its the minimum linearity was 0.072%. The mass loss of polyaniline film after the scour of water was 6.30%, compared with the polyaniline film electropolymerized in hydrochloric acid solution (mass loss 7.55%), it may have better binding force. So the polyaniline modified carbon fiber composite electrode would be utilized to develop a new generation of low-cost, high-performance electric field sensors.