Incorporation of natural lithium-ion trappers into graphene oxide nanosheets

Lithium consumption is estimated to face a considerable rise in the next decade; thus, finding new reproducible lithium resources such as brine deposits and seawater has become a fast-growing research topic. However, Li⁺ extraction from these resources is challenging due to its low concentration and presence of other monovalent cations exhibiting identical chemical properties. Here, it is discovered that tannic acid (TA) inside graphene oxide (GO) nanochannel acts as natural ion trapper, which possesses lithiophilic elements. The lithium-rich feed is achieved by using the potential-driven TA-GO membrane by excluding lithium ions from other monovalent cations. The results showed that the ion trapping capability of inexpensive TA-GO membrane is Li⁺ > Na⁺ > K⁺ with Li trapping energy of −593 KJ mol⁻¹, respectively, where its trapping efficiency goes into a top rank among their expensive synthetic counterparts. Evaluating the combined effect of three key parameters, including barrier energy, hydration energy, and binding energy illustrates that required energy to transport Li-ion through the membrane is higher than that for other monovalent. This proof-of-concept work opens up an avenue of research for designing a new class of ion-selective membranes, based on the incorporation of naturally low cost available lithiophilic guest molecules into 2D membranes.