Surface plasmon mediates the visible light–responsive lithium–oxygen battery with Au nanoparticles on defective carbon nitride

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.