Carbon sheet-decorated graphite felt electrode with high catalytic activity for vanadium redox flow batteries

A carbon sheet-decorated graphite felt electrode was synthesized by in situ polymerization and subsequent high-temperature calcination under an inert atmosphere. The resultant material brings an improved wettability, numerous defect sites, and abundant O, N and P elements as additional catalytic sites to elevate the reaction kinetics and efficiency of vanadium redox flow batteries (VRFBs). The unique CS modifier enriches electrolyte diffusion pathways, which even show a unique capillary flow. The GF@CS displays a high catalytic activity towards the VO ²⁺ /VO ₂ ⁺ , V ³⁺ /VO ²⁺ and V ²⁺ /V ³⁺ oxidation-reduction couples and a reduced cathodic and anodic peak potential difference of 355 mV (vs. 564 mV for GF). The improvement to the electrode results in a GF@CS-based battery presenting an increased capacity of 20.8 Ah L ⁻¹ compared to 13.0 Ah L ⁻¹ of the GF-based battery and an increase in power density from 225 mA cm ⁻² to 300 mA cm ⁻² . Furthermore, the battery exhibited a 74.79% energy efficiency (EE) at 150 mA cm ⁻² , with no attenuation even at 300 cycles. GF@CS greatly elevates the reaction kinetics and efficiency of VRFBs.