Sensing the ocean electric fields via a self-supported CNT sponge

A self-supported CNT sponge is composed of uniformly twisted CNTs with high aspect ratio that enables the large specific surface area and good carrier conduction to go beyond the conventional carbon-based materials, shedding light on its high electrochemical activity in salt water. Herein, we demonstrate the comparable performance of the CNT sponge as the electrode pair to the most commonly used Ag/AgCl for sensing underwater electric fields. The CNT sponge electrodes exhibit a high electrochemical reactivity in salt water with a low noise of ∼10 nV/rt(Hz)@100 Hz within a wide range of the electric field frequency (e.g., 10–105 Hz), while the frequency response approaches a constant magnitude across the same range of frequency. The performance of the CNT sponge electrodes in ocean electric field sensing is further verified by measuring the electrical signal response curve at various characteristic frequencies within a small water container, and also under a simulated source within the water pool. The high chemical stability and low costs of carbon-based CNT sponges pave the way to their potential applications.