Ag/Sn Dual‐Atoms with Synergistic Electrocatalysis for High‐Power Density Vanadium Flow Batteries

Abstract Electrocatalyst with high activity is crucial to improve the power density of a vanadium flow battery (VFB), which is one of the most promising technologies in long duration large‐scale energy storage. However, the accelerated redox reaction of vanadium ions normally accompanies hydrogen evolution as well. Herein, the Ag/Sn dual atoms electrocatalysts (Ag/Sn‐DAs) are reported, exhibiting both high electrocatalytic activity and hydrogen evolution overpotential. Electrochemical in situ characterization indicates that the Ag/Sn‐DAs can significantly promote the dehydration of [V(H₂O)₆]³⁺/[V(H₂O)₆]²⁺ and effectively inhibit hydrogen evolution reaction (HER). Theoretical calculations reveal that the optimized electronic structure and d‐band center of Ag by the adjacent Sn change the ^*H adsorption sites and reduce the dehydration energy barrier of [V(H₂O)₆]³⁺/[V(H₂O)₆]²⁺. As a result, a VFB single cell assembled with Ag/Sn‐DAs decorated graphite felt (GF) electrode delivers a high energy efficiency (EE) of 81.2% at a current density of 200 mA cm⁻² and a peak power density of 925 mW cm⁻², which is much higher than pristine GF (66.7% and 700 mW cm⁻²). This work presents a paradigm for synergistic catalysis in VFBs.