Vanadium flow batteries (VFBs) are considered one of the most promising candidates for large-scale energy storage. However, VFBs suffer from relatively low power density due to severe electrochemical polarization. Herein, we report Bi single atoms supported by an N-doped carbon-regulated graphite felt electrode (Bi SAs/NC@GF) with high electrocatalytic activity and stability, owing to the greatly improved active sites and optimized Bi–N₄ configuration. Electrochemical in situ characterization and theoretical calculations elucidate the desolvation process and specific inner sphere reaction mechanism of [V(H₂O)₆]³⁺/[V(H₂O)₆]²⁺. As a result, a VFB single cell assembled with Bi SAs/NC@GF achieves a much higher energy efficiency of 81.1% at 240 mA cm^–2 than NC@GF (70.5%). Moreover, a 5 kW VFB stack equipped with Bi SAs/NC@GF is assembled for the first time and ran stably for over 400 cycles. This work confirms that a single-atom catalyst is efficient for scalable VFBs with high power density and low cost.

中文翻译：

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铋单原子调节石墨毡电极增强高功率密度钒液流电池


钒液流电池（VFB）被认为是大规模储能最有前途的候选者之一。然而，由于严重的电化学极化，VFB 的功率密度相对较低。在此，我们报道了由氮掺杂碳调节石墨毡电极（Bi SAs/NC@GF）支撑的Bi单原子，由于大大改善的活性位点和优化的Bi-N ₄构型，具有高电催化活性和稳定性。电化学原位表征和理论计算阐明了[V(H ₂ O) ₆ ] ³⁺ /[V(H ₂ O) ₆ ] ²⁺的去溶剂化过程和具体的内球反应机理。因此，用 Bi SAs/NC@GF 组装的 VFB 单电池在 240 mA cm ^–2下的能效比 NC@GF (70.5%) 高得多，达到 81.1%。此外，首次组装了配备 Bi SAs/NC@GF 的 5 kW VFB 电堆，并稳定运行了 400 多个循环。这项工作证实，单原子催化剂对于具有高功率密度和低成本的可扩展 VFB 是有效的。