Metal-Organic Framework with Dual Excitation Pathways as Efficient Bifunctional Catalyst for Photo-assisted Li-O 2 Batteries.

Li-O 2 batteries (LOBs) have sparked significant interest due to their fascinating high theoretical energy density. However, the large overpotential for the formation and oxidation of Li 2 O 2 during charge and discharge process seriously hinders the further development and application of LOBs. In this work, metal-organic frameworks (MOFs) with different metal clusters (Fe, Ti, Zr) are successfully synthesized, and they are employed as the photoelectrodes for the photo-assisted LOBs. The special dual excitation pathways of Fe-MOF under illumination and the superior separation efficiency of photocarriers, which significantly enhance the activation of O 2 /Li 2 O 2 , improving the catalytic activity of oxygen reduction reaction and oxygen evolution reaction. Moreover, compared to traditional inorganic semiconductor crystals, Fe-MOF exhibits large specific surface area and excellent O 2 adsorption ability. Therefore, the LOB with Fe-MOF as the cathode exhibits large specific capacity, ultralow charge/discharge overpotential of 0.22 V at 0.05 mA cm -2 and excellent stability of 195 cycles under illumination. This study provides an environmentally friendly and highly efficient photocatalyst for LOBs, and a new strategy for designing photoelectrodes.