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

Abstract

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.

Photoelectrochemistry of oxygen in rechargeable Li–O2 batteries

“…11b shows the plasmon-enhanced effect on the heterojunction of plasmonic Au nanoparticles decorated on defective C 3 N 4 (Au/N V -C 3 N 4 ). 38 This provides Au/N V -C 3 N 4 with extended light harvesting, a long carrier lifetime of 3.23 ns, and good surface photo-voltage spectroscopy (SPV) signals. A small discharge/ charge voltage gap of 0.27 V at 0.25 mA cm À2 upon visible light is obtained in the Li-O 2 battery.…”

Internal Electric Field and Interfacial Bonding Engineered Step‐Scheme Junction for a Visible‐Light‐Involved Lithium–Oxygen Battery

“…Incorporating light energy into Li–O 2 batteries has been demonstrated as an effective way to lower the large voltage hysteresis, [13–16] in which the energy levels for photo‐excited electrons and holes on semiconductor cathodes have to match with the oxygen reduction and evolution reactions (ORR/OER) during discharge and charge [17–19] . However, the most employed semiconductor materials only allow for ultraviolet light absorption with limited solar energy utilization [20–24] . Simultaneously, they suffer from the severe recombination of photoelectron‐hole pairs and the induced mismatch between carrier lifetime and oxygen redox kinetics at cathodes.…”

Molybdenum Disulfide–Zinc Oxide Photocathodes for Photo-Rechargeable Zinc-Ion Batteries

“…Finally, the band gap of MoS 2 (∼1.9 eV) is lower than those of V 2 O 5 (∼2.2 eV) and VO 2 (∼2.3 eV) and therefore better suited for solar energy harvesting, though ideally, lower band gap materials would be used. Finally, the photoconversion efficiencies of the photobatteries might be improved further through the incorporation of photoactive materials such as plasmonic nanoparticles or organic materials with photocathodes to allow efficient light harvesting, separation, and transportation of photocharge kinetics. − …”