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, CoS 2 /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 − /I 3 − and S 2− /S x 2− redox reactions by improving absorptivity of charged ions and promoting charge transfer. The polysulfide/iodide flow battery with the graphene felt-CoS 2 /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.

Converting CO2 into value-added fuels or chemical feedstocks through electrochemical reduction is one of the several promising avenues to reduce atmospheric carbon dioxide levels and alleviate global warming. This approach...

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Platinum (Pt)-based alloys are considerably promising electrocatalysts for the reduction of I/I and Co/Co redox couples in dye-sensitized solar cells (DSSCs). However, it is still challenging to minimize the dosage of Pt to achieve comparable or even higher catalytic efficiency. Here, by taking full advantages of the Mott-Schottky (M-S) effect at the metal-semiconductor interface, we successfully strategize a low-Pt-based M-S catalyst with enhanced electrocatalytic performance and stability for the large-scale application of DSSCs. The optimized M-S electrocatalyst of NiS-PtX (X = Fe, Ni) heteronanorods is constructed by rationally controlling the ratio of Pt to transition metal in the hybrids. It was found that the electrons transferred from NiS to PtX at their interface under the Mott-Schottky effect result in the concentration of electrons onto PtX domains, which subsequently accelerates the regeneration of both I/I and Co/Co redox shuttles in DSSCs. As a result, the DSSC with NiS-PtFe manifests an impressive power conversion efficiency (PCE) of 8.79% and 5.56% for iodine and cobalt-based electrolyte under AM1.5G illumination, respectively. These PCEs are obviously superior over those with NiS-Pt, PtFe, NiS, and pristine Pt electrodes. The strategy reported here is able to be further expanded to fabricate other low-Pt-alloyed M-S catalysts for wider applications in the fields of photocatalysis, water splitting, and heterojunction solar cells.