In Situ Mechanistic Study of Plasmon-Governed Reaction Pathways in Li-O2 Batteries With a Au@MOF Cathode

Abstract

Lithium-oxygen (Li-O-2) batteries offer a high theoretical energy density (similar to 3600 Wh kg(-1)) but remain hindered by large recharge (RC) overpotentials, low efficiency, and limited cycle life. Integrating solar energy through localized surface plasmon resonance (LSPR) provides a sustainable route to overcome these challenges. Here, gold nanoparticles (Au NPs) were embedded into a UiO-66-NH2 metal-organic framework via a one-step "ship-in-a-bottle" method without capping agents, yielding Au@UiO-66-NH2 with high structural integrity, enhanced visible-light absorption, and improved charge transport. Under illumination, the plasmon-governed Li-O-2 battery exhibited striking morphological changes in discharge (DC) products, forming thin and film-like lithium peroxide (Li2O2) that decomposed more readily during RC. In Situ Fourier transform infrared spectroscopy confirmed LSPR-driven selective Li2O2 formation with suppressed lithium carbonate and carboxylate side-products. UV-vis, band alignment, and time-resolved photoluminescence studies revealed efficient electron transfer from UiO-66-NH2 to adjacent Au sites. Density functional theory further showed that electron-rich Au@UiO-66-NH2 interfaces lower energy barriers for both oxygen reduction and evolution reactions. The system delivered a low overpotential of 1.05 V in the first DC-RC cycle and stable performance for over 600 h under light irradiation, with minimal Au loading (3.04 wt%). This work establishes a new benchmark for efficient, durable, and solar-integrated Li-O-2 energy storage.