N‐ and P‐co‐doped Graphite Felt Electrode for Improving Positive Electrode Chemistry of the Vanadium Redox Flow Battery

Abstract

Abstract In this study, N‐ and P‐co‐doped carbon derived from microcrystalline cellulose, and diammonium hydrogen phosphate ((NH 4 ) 2 HPO 4 ) were employed as the catalyst for / redox reaction. Doping with P enhanced the onset potential and the presence of N (in the form of pyridinic‐ and pyrrolic‐N) and P together enhanced the peak current for the / redox reaction. Further, the doping improved the wettability of the catalyst, thereby increasing the interfacial area available for the reaction. The use of N‐ and P‐co‐doped catalyst coated graphite felts in the vanadium redox flow battery (VRFB) yielded higher energy efficiency and discharge capacity, especially at higher current densities in contrast to un‐doped graphite felt (GF). 100 cycles of charge‐discharge with minimal capacity fade were demonstrated while using N‐ and P‐co‐doped catalyst at the positive electrode of the VRFB.