Photoelectrochemical lithium extraction

Abstract

The direct conversion of solar energy to valuable chemicals by mimicking the photosynthesis of natural leaves, known as artificial leaves, is promising for utilizing renewable energy. Herein, we demonstrate the successful extraction of lithium (Li) from natural brine using a photoelectrochemical (PEC) system, combined with a Li-selective membrane process. A Si photoelectrode, with three p–n junctions connected in series (3S-Si), was seamlessly embedded into an H-cell with two compartments separated by a Li1+xAlxGe2−x(PO4)3 membrane. The unassisted PEC Li extraction was performed under AM 1.5 G illumination without other external energy input. The Li concentration in the enriched solution reached 2924.96 ppm with 99.4 % atomic selectivity after two PEC stages, and the solar-to-Li extraction efficiency reached 0.355 %. Finally, we obtained the valuable product Li2CO3 with 99.93 % purity. Economic analysis revealed that this solar-driven Li extraction system was more profitable than the PEC systems for H2 generation, N2 and CO2 reduction. Our study offers a promising approach for Li mining using sustainable energy and improves the economic viability of Li extraction from natural brine.