Aqueous polysulfide/iodide redox flow batteries are attractive for scalable energy storage due to their high energy density and low cost. However, their energy efficiency and power density are usually limited by poor electrochemical kinetics of the redox reactions of polysulfide/iodide ions on graphite electrodes, which has become the main obstacle for their practical applications. Here, CoS₂/CoS heterojunction nanoparticles with uneven charge distribution, which are synthesized in situ on graphite felt by a one-step solvothermal process, can significantly boost electrocatalytic activities of I⁻/I₃⁻ and S²⁻/S_x²⁻ redox reactions by improving absorptivity of charged ions and promoting charge transfer. The polysulfide/iodide flow battery with the graphene felt-CoS₂/CoS heterojunction can deliver a high energy efficiency of 84.5% at a current density of 10 mA cm⁻², a power density of 86.2 mW cm⁻² and a stable energy efficiency retention of 96% after approximately 1000 h of continuous operation.

Novel Bi₂S₃/Bi₂O₂CO₃ heterojunction photocatalysts were prepared by a simple chemical reaction from commercial Bi₂O₂CO₃. The photocatalytic activities of Bi₂S₃/Bi₂O₂CO₃ were evaluated by degrading Rhodamine B (RhB) under visible light and sunlight irradiation. Further investigation revealed that the content of loading bismuth sulfide (Bi₂S₃) had important effects on the photocatalytic activity of the Bi₂S₃/Bi₂O₂CO₃ heterojunctions, and the 5 mol% Bi₂S₃/Bi₂O₂CO₃ heterojunction photocatalyst exhibited the best photocatalytic activity (30 min under visible light, λ > 400 nm). The high photocatalytic activity could be attributed to its good visible light absorption, facilitated charge separation of photogenerated electron–hole pairs and efficient charge transfer path in the partly exposed core in the heterojunctions. These benefits are derived from the unique band gap structure of the Bi₂S₃/Bi₂O₂CO₃ n–n-type heterojunctions and special morphology with the partly exposed core, which was confirmed by photoluminescent spectra, surface photovoltage spectra and photoelectrochemical characterizations.

B-Doped pSi exhibits an exceptionally high initial coulombic efficiency of 89% and shows outstanding cycling performance (reversible capacity of 1500 mA h g ⁻¹ at 2 A g ⁻¹ after 300 cycles).