Electrodes with metal-based electrocatalysts for redox flow batteries in a wide pH range

Redox flow batteries (RFBs) with decoupling energy and power, high safety, long durability and easy scalability have been considered as giant promising candidates for large-scale energy storage systems. As a key component of RFBs, the electrodes provide active sites for the conversion between electrical and chemical energies. Thus, the electrochemical properties of both the positive and negative electrodes are significantly important to the performance of batteries, especially the energy efficiency and the power. Therefore, improving the electrochemical performance of electrodes by effective modifications is essential for the advancements of RFBs. With high conductivity, high activity and stability, metal-based electrocatalysts have been widely used to modify and increase the electrochemical activities of electrodes in RFBs. This review summarizes and discusses the applications of metal-based electrocatalysts modified carbon-based electrodes of RFBs in a wide pH range (the acidic, alkaline and neutral electrolytes), including the characterizations of physicochemical and electrochemical properties of electrodes, the cell performance, the merits, and limitations.