Multilayered Graphene-Coated Metal Current Collectors with High Electrical Conductivity and Corrosion Resistivity for Flow-Electrode Capacitive Mixing

Abstract

Flow-electrode capacitive mixing (F-CapMix) is a novel technology, harvesting electric energy from salinity gradient power. A continuously circulating flow-electrode enables constant electrical power generation without any intermittent step. Graphite is a widely used current collector because of its high electrical conductivity and corrosion resistivity to seawater for F-CapMix. However, insulating polyacrylate-based polymers should be employed for shaping the graphite body, resulting in reduced electrical conductivity, hindering efficient charge percolation in flow-electrodes. Metal current collectors are difficult to use because of their low corrosion resistance to seawater despite their good electrical conductivity. Here, we first report high electrical conductivity and corrosion-resistive multilayered graphene as a protective layer on metal current collectors in F-CapMix. The graphene is synthesized on metal current collectors through the chemical vapor deposition process. We study chemical and electrochemical aspects of protective layer-coated current collectors by controlling parameters for graphene growth on metal substrates. The multilayered graphene protective layer can not only prevent corrosion from seawater but also enable efficient charge percolation with high electrical conductivity. By employing multilayered graphene-coated Ni current collectors in the F-CapMix unit cell, an almost twice higher power density of 0.75 W·m–2 and current density of 22.3 A·m–2 could be achieved compared to those of graphite.