Ambient-condition CO₂laser direct writing of graphitic and functional groups coating at 3D graphite felt electrode for enhanced-redox flow batteries performance

Redox flow batteries (RFBs) play a pivotal role in sustainable grid-scale energy storage applications. Graphite felt electrode is widely used in RFB as an electrode on both the anode and cathode sides, which determines electrochemical performance. However, sluggish electrode kinetics at the interface restrict the redox-active electrolyte utilization of the pristine graphite felt electrode. Here, we present a distinct strategy by introducing a foreign species at the graphite felt electrode that facilitates the redox kinetics, thus improving the RFB performance. We polymerize furfuryl alcohol (FA), a bio-waste-derived precursor, at the felt and subsequently expose it to infrared radiation from a CO₂ laser under ambient conditions. Surface analysis confirms that the polymerized material (polyfurfuryl alcohol, PFA) at the graphite felt electrode converts to the hydrophilic functional group-rich graphitic coating and simultaneously induces defects at the graphite felt under the CO₂ laser radiation. A modified graphite felt electrode assembled with quinone-based derivative alizarin and potassium ferrocyanide electrolyte in a full cell RFB, the discharge capacity (mAh) retains ∼57 % and energy efficiency ∼10 % more than compared to the pristine electrode over 260 cycles. Our method provides low-cost bio-waste feedstock and industry-scale laser processing, offering a rapid, cost-effective route to engineer high-performance RFB electrodes.