Li−O 2 batteries are considered the ultimate energy storage technology for their potential to store large amounts of electrical energy in a cost-effective and simple platform. Large overpotentials for the formation and oxidation of Li 2 O 2 during discharging and charging have thus far confined this technology to a scientific curiosity. Herein, we consider the role of catalytic intervention in the reversibility of the cathode reactions and find that semiconducting metal−organic polymer nanosheets composed of cobalt-tetramino-benzoquinone (Co-TABQ) function as a bifunctional catalyst that facilitates the kinetics of the cathode reactions under visible light. Upon discharging, we report that O 2 is first adsorbed on the Co atoms of Co-TABQ and accepts electrons under illumination from the d z 2 and d xz orbitals of Co atoms in the π 2p * orbitals, which facilitates reduction to LiO 2 . The LiO 2 is further shown to undergo a second reduction to the discharge product of Li 2 O 2 . In the reverse charge, the holes generated in the d z 2 orbitals of Co are mobilized under the action of the applied voltage to enable the fast decomposition of Li 2 O 2 to O 2 and Li + . Under illumination, the Li−O 2 battery exhibits respective discharge and charge voltages of 3.12 and 3.32 V for a round-trip efficiency of 94.0%. Our findings imply that the orbital interaction of metal ions with ligands in Co-TABQ nanosheets dictates the light harvesting and oxygen electrocatalysis for the Li−O 2 battery.

Li–O2 batteries have aroused considerable interest in recent years, however they are hindered by high kinetic barriers and large overvoltages at cathodes. Herein, a step‐scheme (S‐scheme) junction with hematite on carbon nitride (Fe2O3/C3N4) is designed as a bifunctional catalyst to facilitate oxygen redox for a visible‐light‐involved Li–O2 battery. The internal electric field and interfacial Fe−N bonding in the heterojunction boost the separation and directional migration of photo‐carriers to establish spatially isolated redox centers, at which the photoelectrons on C3N4 and holes on Fe2O3 remarkably accelerate the discharge and charge kinetics. These enable the Li–O2 battery with Fe2O3/C3N4 to present an elevated discharge voltage of 3.13 V under illumination, higher than the equilibrium potential 2.96 V in the dark, and a charge voltage of 3.19 V, as well as superior rate capability and cycling stability. This work will shed light on rational cathode design for metal–O2 batteries.

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.

Developing earth-rich highly efficient nonprecious electrocatalysts for hydrogen evolution reaction (HER) has become of great significance for sustainable energy technology. Herein, novel nickel foam (NF) supported porous featherlike NiCoP (PF-NiCoP/NF) nanoarrys are constructed by a successive hydrothermal and phosphidation way. Simultaneously, their three-dimensional (3D) morphology, the holey structure, and the conductive substrate are favorable for the enhanced specific surface area, efficient electron and mass transfer, and exposure of more active sites, and also are beneficial for the release of generated H2. PF-NiCoP/NF demonstrates high activity and long-term durability in alkaline media (1 M KOH) and real seawater, reaching the current density of 10 mA cm–2 at overpotentials of 46 and 287 mV, respectively. Moreover, the faradaic efficiency of 3D PF-NiCoP/NF is as high as 96.5% in real seawater. As expected, PF-NiCoP/NF exhibits superior performance in comparison to those of most of HER electrocatalysts in real seawater and alkaline media. This work may present a new strategy to design a promising electrocatalyst superior to platinum in a wide range of pH and may provide a new idea for electrocatalytic seawater splitting.

Non-aqueous Li−O 2 batteries have aroused considerable attention because of their ultrahigh theoretical energy density, but they are severely hindered by slow cathode reaction kinetics and large overvoltages, which are closely associated with the discharge product of Li 2 O 2 . Herein, hexagonal conductive metal−organic framework nanowire arrays of nickel-hexaiminotriphenylene (Ni-HTP) with quadrilateral Ni-N 4 units are synthesized to incorporate Ru atoms into its skeleton for NiRu-HTP. The atomically dispersed Ru-N 4 sites manifest strong adsorption for the LiO 2 intermediate owing to its tunable d-band center, leading to its high local concentration around NiRu-HTP. This favors the formation of film-like Li 2 O 2 on NiRu-HTP with promoted electron transfer and ion diffusion across the cathodeelectrolyte interface, facilitating its reversible decomposition during charge. These allow the Li−O 2 battery with NiRu-HTP to deliver a remarkably reduced charge/ discharge polarization of 0.76 V and excellent cyclability. This work will enrich the design philosophy of electrocatalysts for regulation of kinetic behaviors of oxygen redox.