Two-dimensional Materials for Osmotic Energy Conversion

Osmotic energy conversion, the extraction of power from the salt difference between river water and seawater, is a crucial way to solve the energy crisis in future. Osmotic energy attracts extensive attention and research due to its huge reserves, easy accessibility, and sustainability. Ion-exchange membrane is a key component in reverse electrodialysis (RED) technology for osmotic energy conversion, which immensely impacts the performance of osmotic energy conversion. Two-dimensional (2D) materials such as graphene, graphene oxide, molybdenum disulfide, various frame materials and their functionalized composites have become prospective materials for harvesting osmotic energy on account of their excellent ion selective transport , nanoscale pores or channels, abundant functional groups, and modifiability. In this review, we summarize the types of 2D materials as ion transport channels and their corresponding transport mechanisms. Furthermore, we also discuss the current state of the art in designs and show the applications of 2D materials and their composites in osmotic energy conversion. Finally, we overview the challenges of 2D materials in osmotic energy conversion and propose future directions of research.