Robust nickel single-atom catalyst for high-efficiency and stable vanadium-cerium redox flow batteries

Abstract

Vanadium-cerium redox flow batteries (V-Ce RFBs) have emerged as a promising alternative to all-vanadium systems due to the lower cost and high standard redox potential of Ce³⁺/Ce⁴⁺. However, their practical application is hindered by the sluggish kinetics of the Ce³⁺/Ce⁴⁺ redox reaction and the severe corrosion of conventional graphite felt electrodes. To address these challenges, we constructed a single atomic nickel catalyst (Ni₁/NC) with a four-nitrogen coordination structure (Ni₁–N₄ moiety) on nitrogen-doped carbon support. The Ni₁/NC catalyst with high Ni loading possesses abundant accessible active sites and unique structure properties for catalysis. When applied as a positive electrode, the Ni₁/NC catalyst exhibited significantly enhanced electrocatalytic activity and stability for Ce³⁺/Ce⁴⁺ redox. The assembled V-Ce RFBs achieves a high energy efficiency of 69.1% at 200 mA cm^-2 and a superior peak power density, markedly outperforming cells with baseline electrodes. Density functional theory calculations reveal that the Ni₁–N₄ sites facilitate charge transfer and enhance activation of reactant species (Ce⁴⁺), providing atomic-level insight into the catalytic mechanism. This work demonstrates the effectiveness of single-atom catalysts in enhancing the performance of V-Ce RFBs and sheds light on designing advanced electrocatalysts.

Keywords

Redox flow batteries / vanadium-cerium / redox reaction kinetics / single atom catalysts

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