A phosphotungstic acid coupled silica-Nafion composite membrane with significantly enhanced ion selectivity for vanadium redox flow battery

An ultra-high ion-selective Nafion composite membrane modified by phosphotungstic acid(PWA)coupled silica for vanadium redox flow battery(VRB)was constructed and prepared through solution casting.The composite membrane exhibits excellent proton conductivity and vanadium ions blocking property by incorporating the nanohybrid composed of silica and PWA into the Nafion ionomer.Simple tuning for the filling amount of the nanohybrid endows the obtained membranes preeminent vanadium barrier property including a minimum vanadium permeability of 3.13×10-7cm2min-1and a maximum proton conductivity of 0.081 S cm-1at 25°C.These indicate an ion selectivity of 2.59×105S min cm-3,which is 6.8times higher than that of recast Nafion(0.33×105S min cm-3).As a result,the VRB with the composite membrane shows superior battery performance containing a lower self-discharge rate,higher capacity retention and more robust cyclic stability compared with recast Nafion over a range of current densities from 40 to 100 m A cm-2.

Strategies and Mechanism for Enhancing Intrinsic Activity of Metal–Nitrogen–Carbon Catalysts in Electrocatalytic Reactions

Atomically dispersed metal-nitrogen-carbon catalysts(M-N-C)have been widely used in the field of energy conversion,which has high commercial application value in future directions.However,the commercialization of M-N-C catalysts necessitates further requirements for their catalytic activity,especially their intrinsic catalytic activity.Fortunately,current research has provided many modification strategies,which are of great significance for the development of M-N-C catalysts.In this review,the catalytic mechanism of different electrocatalytic reactions is briefly introduced.In addition,intrinsic catalytic activity enhancement strategies are systematically summarized,including the coordination structure,carrier effect,and interaction of active centers.Furthermore,we focus on clarifying the relationship between microelectronic structure and macro-catalytic activity of M-N-C catalysts in different electrochemical energy conversion reactions.The future research directions are also pointed out based on our discussion.This review provides good guidance to systematically study the intrinsic catalytic activity enhancement strategies of M-N-C catalysts and reasonably design highly catalytic M-N-C catalysts.