{"title":"Redox Couples","description":"\u003cp\u003e\u003cstrong\u003eRedox couples are the working chemistry of a flow battery — the dissolved species whose oxidation state cycles between charge and discharge, setting cell voltage, energy density, and the bounds of every other component choice.\u003c\/strong\u003e This collection groups the active electrolytes and precursor salts used to build aqueous and non-aqueous flow cells at lab and pilot scale, organized by chemistry family so you can match a couple to your stack, membrane, and target duty cycle.\u003c\/p\u003e\n\n\u003ch3\u003eAll-vanadium\u003c\/h3\u003e\n\u003cp\u003eThe reference chemistry for stationary storage. VOSO4 and vanadium pentoxide precursors dissolved in concentrated sulfuric acid give you a single-element system on both sides — the V2+\/V3+ negolyte and VO2+\/VO2+ posolyte — which removes cross-contamination as a failure mode and is why all-vanadium remains the baseline for benchmarking new membranes and electrodes. Use this family when you are testing PFSA or hydrocarbon ion-exchange membranes, characterizing felt or paper electrodes, or running long-cycle stability work where capacity fade has to be unambiguously attributable.\u003c\/p\u003e\n\n\u003ch3\u003eIron-chromium and all-iron\u003c\/h3\u003e\n\u003cp\u003eLower-cost aqueous couples aimed at price-per-kWh rather than peak energy density. Iron-chromium uses FeCl2\/FeCl3 against CrCl3 in HCl; all-iron pairs Fe(II)\/Fe(III) with iron plating on the negative side. Suited to long-duration storage research where abundance of the active material matters more than volumetric energy.\u003c\/p\u003e\n\n\u003ch3\u003eZinc-bromine and zinc-based hybrids\u003c\/h3\u003e\n\u003cp\u003eHybrid flow chemistries where zinc plates onto the negative electrode while a soluble bromine complex cycles on the positive. ZnBr2 with bromine-sequestering quaternary ammonium agents is the classic formulation; useful when you need higher cell voltage and energy density than all-vanadium and can accept a plating-limited negative.\u003c\/p\u003e\n\n\u003ch3\u003eOrganic and quinone-based couples\u003c\/h3\u003e\n\u003cp\u003eAqueous and non-aqueous organic actives — anthraquinone sulfonates, viologens, TEMPO derivatives, ferrocene derivatives — for groups developing metal-free or tunable-potential systems. Solubility, stability against nucleophilic attack, and crossover through the separator are the dominant questions here, and the couple choice drives membrane selection more than in vanadium work.\u003c\/p\u003e\n\n\u003cp\u003eIf you are building a vanadium baseline cell, start with the vanadium precursors and pair them with carbon felts and PFSA membranes from Electrodes and Membranes. For organic-active research, also see Supporting Electrolytes and the broader \u003ca href=\"\/collections\/redox-flow-battery\"\u003eRedox Flow Battery\u003c\/a\u003e section.\u003c\/p\u003e\n","products":[],"url":"https:\/\/echemsupplies.com\/collections\/redox-couples.oembed","provider":"EChem Supplies","version":"1.0","type":"link"}