Hydrogen/functionalized benzoquinone for a high-performance regenerative fuel cell as a potential large-scale energy storage platform

Abstract

The redox flow battery (RFB) is a suitable option for electricity storage due to its high energy efficiency, scalability and relative safety. However, the limited metallic resources for redox materials and the high cost of systems such as the all-vanadium RFB are major challenges for its wider application. Organics may be sourced more abundantly and have lower prices than metal based redox couples. In this work a regenerative fuel cell involving relatively inexpensive organic redox couples is demonstrated. The electrochemical properties of 1,2-dihydrobenzoquinone-3,5-disulfonic acid (BQDS) are characterised by cyclic voltammetry and linear-sweep voltammetry under hydrodynamic conditions. A regenerative fuel cell using 0.65 M BQDS in 1 M H₂SO₄ as the positive electrolyte and gaseous hydrogen (1 bar) as the negative redox-material exhibits an open circuit cell voltage of 0.86 V, a power density of 122 mW cm⁻², and an energy density of 10.90 W h L⁻¹ without considering the volume occupied by the hydrogen. A very promising performance with an energy efficiency >60% at 100 mA cm⁻² for 200 cycles is reported. New organic redox species resistant to side reactions could facilitate the use of this new system in practical applications. The use of hydrogen may also contribute to reduced side reactions of the organic redox material associated with degradation in the presence of oxygen.