▎ 摘　　要

Salinity gradient energy (SGE) is the energy available from the salinity difference between freshwater and saltwater. Herein, we propose a concentration capacitor as a novel capacitive mixing (CapMix) technique to harvest SGE. The concentration capacitor comprises identical electrodes and a membrane that separates concentrated and diluted solutions that alternately flow through the capacitor. Graphene hydrogel (GH) electrodes and a filtration membrane (FM) or an anion exchange membrane (AEM) are used to construct GH//FM//GH and GH//AEM//GH concentration capacitors. These concentration capacitors show excellent performance in harvesting SGE, particularly the GH//AEM//GH concentration capacitor, whose voltage rise and average power density can reach 288.5 mV and 482.4 mW m(-2), respectively, which are higher than those obtained with other CapMix techniques. The outstanding performance is associated with the double-channel construction, the membrane potential, and the macroporous structure and abundant negative charge of the GH electrodes. Our results show that the concentration capacitor is a promising approach for efficiently extracting SGE.