Design of Photothermal "Ion Pumps" for Achieving Energy-Efficient, Augmented, and Durable Lithium Extraction from Seawater.

Abstract

Extracting lithium from seawater has emerged as a disruptive platform to resolve the issue of an ever-growing lithium shortage. However, achieving highly efficient and durable lithium extraction from seawater in an energy-efficient manner is challenging, as imposed by the low concentration of lithium ions (Li⁺) and high concentration of interfering ions in seawater. Here, we report a facile and universal strategy to develop photothermal "ion pumps" (PIPs) that allow achieving energy-efficient, augmented, and durable lithium extraction from seawater under sunlight. The key design of PIPs lies in the function fusion and spatial configuration manipulation of a hydrophilic Li⁺-trapping nanofibrous core and a hydrophobic photothermal shell for governing gravity-driven water flow and solar-driven water evaporation. Such a synergetic effect allows PIPs to achieve spontaneous, continuous, and augmented Li⁺ replenishment-diffusion-enrichment, as well as circumvent the impact of concentration polarization and scaling of interfering ions. We demonstrate that our PIPs exhibit dramatic enhancement in Li⁺ trapping rate and outstanding Li⁺ separation factor yet have ultralow energy consumption. Moreover, our PIPs deliver ultrastable Li⁺ trapping performance without scaling even under high-concentration interfering ions for 140 h operation, as opposed to the significant decrease of nearly 55.6% in conventional photothermal configuration. The design concept and material toolkit developed in this work can also find applications in extracting high-value-added resources from seawater and beyond.