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

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 VO 2þ /VO þ 2 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 VO 2þ /VO þ 2 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.[a] V.

Styrene-co-DVB grafted PVDF proton exchange membranes for vanadium redox flow battery applications

“…Water uptake for HA-35 was found to be 41.5%, and 46% for the HA-45 membrane. 41,42 The enhancement in water uptake was due to the presence of large number of functional groups in the HA-45 membrane compared to the HA-35 membrane, and the functional groups also increased water uptake ( Table 1). The expansion was proportional to the water uptake, and as the water uptake increased, the membrane expansion also increased, and the valencies of hydrophobic and hydrophilic regions maintained the expansion ratio and only 22% for HA-35 and 28% for HA-45 was noted, which was quite reasonable for IEMs.…”

“…[37][38][39] Due to the highly oxidative and reducing environment of the catholyte and anolyte in the VRFB it is very difficult to sustain the stability of the membrane as there may be a possibility of leaching of the fillers. [40][41][42][43] Maintaining stability of the membrane without compromising the ionic conductivity in the VRFB environment is an important parameter.…”

N, S and Transition-Metal Co-Doped Graphene Nanocomposites as High-Performance Catalyst for Glucose Oxidation in a Direct Glucose Alkaline Fuel Cell

“…In particular, heteroatom doping was effective on the increase of active sites and regulation of electron distribution [ 18 , 19 , 20 , 21 , 22 ]. It has been demonstrated that co-doping multi elements with different electronegativity can remarkably improve the performance of graphene due to the positive synergistic effect of heteroatoms [ 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 ]. Ci et al [ 35 ] simultaneously doped graphene with nitrogen and loaded cobalt to obtain Co/NG catalyst by heat treatment.…”

Enhanced electrocatalytic performance of nitrogen‐ and phosphorous‐functionalized carbon felt electrode for VO 2 + / VO 2 + redox reaction

“…A majority of the research on developing electrodes via heteroatom doping focuses on introducing single heteroatoms to carbon materials. To the best of our knowledge, in the field of VRFBs, only few studies have investigated N, P co‐doped carbon materials as electrocatalysts for V 4+ /V 5+ redox reaction 33,36 . They reported that the V 4+ /V 5+ redox reaction can be effectively enhanced by introducing N, P co‐doped carbon materials as electrocatalysts on the carbon felt electrode.…”

“…12 Carbonaceous materials co-doped with binary heteroatoms show enhanced electrochemical activity for the oxygen reduction reaction at the cathodes of fuel cells and metal-air batteries because of the increased total number of heteroatoms and the synergetic effect of the co-doped heteroatoms. 25,29,[32][33][34] Interestingly, despite extensive studies on N, P co-doped carbon materials, these carbon materials have rarely been explored for improving the electrochemical performances of VRFBs. A majority of the research on developing electrodes via heteroatom doping focuses on introducing single heteroatoms to carbon materials.…”