分会场

燃料电池与储能

摘要

Marine environmental monitoring is crucial to the development of the marine economy, resources, and military. The underwater energy system is a prerequisite for a marine large-scale observation network. Sailing the high seas, diving into the deep sea, and setting foot in the polar regions are currently hot fields for expanding the boundaries of human cognition, which requires the ocean observation network to provide real-time and accurate information. However, the extreme environment of the ocean (low temperature, low oxygen, high pressure, corrosion, etc.) poses great challenges for underwater energy systems. In order to ensure the efficient, safe, and stable operation of energy systems, materials and devices for extreme environments need to be developed urgently. Dissolved oxygen seawater batteries provide a new paradigm for energy conversion in extreme marine environments—using natural seawater as the electrolyte, metal dissolution as the anodic reaction, and dissolved oxygen reduction as the cathodic reaction to achieve in-situ energy conversion. Therefore, the dissolved oxygen seawater battery has excellent environmental adaptability and long service life, and its open structure avoids the safety problems caused by the huge pressure of the deep sea, which is compatible with the marine environment and has great potential. However, although the total amount of dissolved oxygen in seawater is large, the oxygen concentration is low (seawater: 9.6 mg L–1; air: 310 mg L–1). Besides, unlike the typical three-phase reaction interface of metal-air batteries and fuel cells [1], submerged electrodes of seawater batteries lead to slow kinetics. Low oxygen concentration and slow mass transfer result in low voltage and power of seawater batteries. In the previous work, two oxygen reduction reaction (ORR) catalysts, Fe-N-G/CNT [2] and MW-α-FePc, suitable for seawater oxygen-poor environments were prepared through support regulation and electronic structure design. Fe-N-G/CNT utilizes the charge separation caused by the difference in the Fermi energy level of graphene and carbon nanotubes, which reduces the energy barrier of the rate-determining step of ORR. Besides, the single-atom double-adsorption sites on graphene and carbon nanotubes enhanced the O2 adsorption, which has a significant ORR current response at an extremely low dissolved oxygen concentration (0.4 mg L–1). MW-α-FePc realizes the electronic axial stretching of the Fe active site by regulating the stacking of the planar molecule FePc, which makes the energy level of the dz2 orbital drop close to the Fermi level, narrowing the material band gap and improving its electron transfer during the reaction. In addition, adsorption of OO and OOH is promoted, which facilitates the ORR process. The full battery tests indicate that the above two catalysts have significantly improved the voltage and power density of the battery, as well as the discharge performance in lean-oxygen seawater. This has important significance for catalyst design in extreme environments.

关键词

seawater battery, oxygen reduction reaction, catalyst

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