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.

Vanadium redox flow battery (VRFB) is an energy storage system, wherein V2+/V3+ and VO2+/VO2+ are used as negative and positive electrolyte respectively. It is well known that, V2+/V3+ redox reaction is sluggish in comparison to that of VO2+/VO2+ reaction. As the redox potential of V2+/V3+ redox‐couple is more negative to that of H+/H2 redox‐couple, during the V2+ formation hydrogen evolution occurs concomitantly, which affects the capacity retention of VRFB inducing redox couples concentration imbalance between the positive and negative electrolytes. In this study, we have explored the beneficial effect of D‐fructose as an additive to the negative electrolyte. D‐fructose (i) enhances the interfacial area of the graphite felt negative electrode‐electrolyte interface by wetting, thereby the current due to V2+/V3+ redox reaction at a given overpotential, (ii) suppresses the H2 evolution at negative electrode during charging of VRFB (iii) controls the VO2+ accumulation at the positive electrolyte and (iv) chemically reduces the VO2+ arriving at negative electrode side through crossover, thereby avoiding the direct reaction between V2+ and VO2+. A capacity retention of 86 % and 25 % is achieved at the end of the 25th cycle in the presence and absence of D‐fructose in the negative electrolyte, respectively. This way of in‐situ redox balancing alleviates the requirement for external redox balancing of the electrolyte, and help VRFB to deliver constant capacity with cycles.

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The emergence properties of paper as the ionic conductor has driven the new development in energy generators mainly micro‐nano scale energy. Instead of the flow channels in conventional fuel cells, the capillary action of the paper controls the flow of the electrolytes. Paper based biofuel cells and electrochemical fuel cells are recent trends in micro‐nano power generation to support the biosensors. In this study, zinc fuel and VO2+4pt oxidant were used to form a membraneless fuel cell. Instead of membrane, Whatmann® 2 filter paper was used as the separator cum autonomous microfluidic pumping system. When 6 M KOH and 1.5 M VO2+ in 2.5 M H2SO4 were supplied on the anode and cathode respectively, a peak power density of 9.4 mW cm−2 at 1.21 V and open circuit voltage of ∼ 2.5 V were realized. Due to the low cost and high power associated with this system, it can be used to power the Lab‐on‐Chip devices employed for single use point‐of‐care applications.

Redox flow batteries (RFBs) are considered a vital part of the energy storage system for storing the energy generated from the renewable energy sources such as wind and solar. Limited by the water electrolysis potential window, the aqueous RFBs exhibit low energy density (<25 Wh L −1 ). In this context a non-aqueous organic solvent based RFB system is very attractive as it offers avenue to expand the operating potential window beyond 1.23 V, which has a direct impact on the RFB's energy and power densities. In this study, new redox systems based on tris(4-bromophenyl)amine (4-Br-TPA) and oxygen saturated N,N-dimethylformamide (DMF) containing tetra-n-butylammonium hexafluorophosphate (TBAPF 6 ) are utilized as catholyte and anolyte respectively. Here, TBAPF 6 performs dual role, both as supporting electrolyte and a stabilizer of superoxide anion radical.