Aprotic lithium-oxygen (Li-O2) batteries have gained extensive interest in the past decade, but are plagued by slow reaction kinetics and induced large-voltage hysteresis. Herein, we use a plasmonic heterojunction of Au nanoparticle (NP)-decorated C3N4 with nitrogen vacancies (Au/NV-C3N4) as a bifunctional catalyst to promote oxygen cathode reactions of the visible light-responsive Li-O2 battery. The nitrogen vacancies on NV-C3N4 can adsorb and activate O2 molecules, which are subsequently converted to Li2O2 as the discharge product by photogenerated hot electrons from plasmonic Au NPs. While charging, the holes on Au NPs drive the reverse decomposition of Li2O2 with a reduced applied voltage. The discharge voltage of the Li-O2 battery with Au/NV-C3N4 is significantly raised to 3.16 V under illumination, exceeding its equilibrium voltage, and the decreased charge voltage of 3.26 V has good rate capability and cycle stability. This is ascribed to the plasmonic hot electrons on Au NPs pumped from the conduction bands of NV-C3N4 and the prolonged carrier life span of Au/NV-C3N4 This work highlights the vital role of plasmonic enhancement and sheds light on the design of semiconductors for visible light-mediated Li-O2 batteries and beyond.
Keywords: oxygen evolution; oxygen reduction; surface plasmon; vacancy; visible light.