Atomic Bi active sites decorated graphite felt derived from bismuth-based metal−organic framework boosting vanadium redox flow battery performance

Abstract

Vanadium redox flow battery (VRFB) is promising large-scale energy storage technology for renewable energies, while the sluggish kinetics of vanadium redox reaction restricts the efficiency at high current density. Herein, the strategy of boosting V²⁺/V³⁺ redox reaction by atomic Bi active sites decorated graphite felt electrode derived from bismuth-based metal−organic framework (Bi-MOF) is proposed. Bi-MOF, dispersing abundant Bi metal sites on porous carrier, helps the Bi atoms to form atomic active sites easily by coordinating with N through the nitrogen source mediated carbonization process. Porous nanobundles of atomic Bi catalyst uniformly bind to the graphite felt, exhibiting over 2 folds increase in specific surface area, higher V²⁺/V³⁺ redox peak currents and reversibility, and one order of magnitude lower of charge-transfer resistance. The atomic Bi active sites decorated graphite felt negative electrode achieves high VRFB performance even with the vanadium ions heavily permeable Nafion membrane, showing 13.1 % higher energy efficiency at 200 mA cm^–2 (80.2 % vs. 70.9%), 68.1% increase in electrolyte utilization comparing to the pristine graphite felt, and keeping stable during 1500 charge/discharge cycles. The performance is superior to the reported metal−organic frameworks (MOFs)-derived catalyst decorated electrodes.