Methylene Blue in a High-Performance Hydrogen-Organic Rechargeable Fuel Cell

A hydrogen-organic hybrid flow battery (FB) has been developed using methylene blue (MB) in an aqueous acid electrolyte with a theoretical positive electrolyte energy storage capacity of 65.4 A h L^-1. MB paired with the versatile H₂/H⁺ redox couple at the negative electrode forms the H₂-MB rechargeable fuel cell, with no loss in capacity (5 sig. figures) over 30 100% discharge cycles of galvanostatic cycling at 50 mA cm^-2, which shows excellent stability. A peak power density of 238 mW cm^-2 has also been demonstrated by utilizing 1.0 M MB electrolyte. This represents a type of scalable electrochemical energy storage system with favorable properties in terms of material cost, stability, crossover management, and energy and power density, overcoming many typical limitations of organic-based redox FBs.