An Auto‐Switchable Dual‐Mode Seawater Energy Extraction System Enabled by Metal–Organic Frameworks

Abstract

Harvesting energy directly in oceans by electrochemical devices is essential for driving underwater appliances such as underwater vehicles or detectors.Owing to the extreme undersea environment, it is important but difficult to use the devices with both ah igh energy density and power density simultaneously.I nspired by marine organisms that have switchable energy extraction modes (aerobic respiration for long-term living or anaerobic respiration to providei nstantaneously high output power for fast movement), an autoswitchable dual-mode seawater energy extraction system is presented to provide high energy density and power density both by initiatively choosing different solutes in seawater as electron acceptors.With assistance from metal-organic frameworks,t his device had at heoretical energy density of 3960 Wh kg À1 ,a nd ah igh practical power density of 100 AE 4mWcm À2 with exceptional stability and low cost, making practical applications in seawater to be possible.Innovative techniques have been developed to address energetic and environmental issues in oceans. [1] Theg reat potential of the marine economy and related research activities prompts rapid development of energy supply systems for underwater devices. [2] To support adequate energy for the devices during long-term operation under sea, generating energy in seawater directly is an essential strategy. [3] Different from many of the seawater energy harvesting devices,e lectrochemical devices can supply stable electricity have therefore been widely utilized. [4] By either using seawater as electrolytes or electron acceptors, underwater appliances have been driven successfully. [5] However,t oa dapt to the extreme and complex conditions, as eawater electrochemical system that can automatically switch between high energy and power modes is greatly needed. In this case,t he underwater devices can not only work for av ery long term, but also can move fast or afford other loads with high power request during as hort term. However,building up such asystem is still abig challenge so far.Marine organisms solve this challenge by cellular respiration. Depending on the required output power, the respiration process can be switched between anaerobic and aerobic by choosing various electron acceptors, [6] making high power and high energy supply possible in one organism. Herein we describe acellular respiration inspired dual-mode energy extraction from seawater by using nanoporous frameworks to initiatively select electron acceptors depending on power output.Our design takes advantage of multivalent coordination frameworks that are assembled from organic ligands and redox-capable metal-containing nodes. [7] When electrons are injected, the coordination frameworks can either transfer the electrons to other acceptors like dissolved oxygen, [8] or store the electrons upon insertion of alkali metal ions. [9] Depending on the electron acceptance pathway,the system works in dual modes.Inthe high-energy working mode (aerobic respiration analogue), the system uses the d...

Metal-Organic Powder Thermochemical Solid-Vapor Architectonics toward Gradient Hybrid Monolith with Combined Structure-Function Features

“…Seawater batteries are widely used in underwater applications and activities. [1][2][3][4][5][6][7][8][9] These batteries use seawater as the electrolyte and generate electricity by transferring electrons from metal anode to cathode. The ideal cathode for metal-based seawater batteries should exhibit many characteristics, including high catalytic activity, high electrical conductivity, good corrosion resistance, excellent mechanical properties, and low fabrication cost.…”