Internal Electric Field and Interfacial Bonding Engineered Step‐Scheme Junction for a Visible‐Light‐Involved Lithium–Oxygen 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. The internal electric field and interfacial Fe−N bonding in S‐scheme Fe2O3/C3N4 significantly boosts the separation and directional migration of photo‐excited carriers to establish spatially isolated redox centers. These enable the light‐involved Li–O2 battery with a Fe2O3/C3N4 cathode to present an elevated discharge voltage of 3.13 V under illumination and a charge voltage of 3.19 V, as well as superior rate capability and cycling stability.