Oxygen vacancy-rich MoO3 nanorods as photocatalysts for photo-assisted Li-O2 batteries

Photo-assisted lithium-oxygen (Li-O-2) batteries have been developed as a new system to reduce a large overpotential in the Li-O-2 batteries. However, constructing an optimized photocatalyst is still a challenge to achieve broad light absorption and a low recombined rate of photoexcited electrons and holes. Herein, oxygen vacancy-rich molybdenum trioxide (MoO3-x) nanorods are employed as photocatalysts to accelerate kinetics of cathode reactions in the photo-assisted Li-O-2 batteries. Oxygen vacancies on the MoO3-x nanorods can not only increase light-harvesting capability but also improve electrochemical activity for the cathode reactions. Under illumination, the photoexcited electrons and holes are effectively separated on the MoO3-x nanorods. During discharging, activated O-2 is reduced to Li2O2 by the photoexcited electrons from the MoO3-x nanorods. The photoexcited holes can promote the decomposition of Li2O2 during subsequent charging. Accordingly, the photo-assisted Li-O-2 batteries with the MoO3-x nanorods deliver an ultralow overpotential of 0.22 V, considerable rate capability, and good reversibility. We think that this work could give a reference for the exploitation and application of the photocatalysts in the photo-assisted Li-O-2 batteries.