High-Potential Pseudocapacitive Energy Storage System: Iron-Based Polyferric Sulfate Electrolyte and Partially Sacrificial Graphite Electrode

Abstract

Tremendous research works including nanofabrication techniques and crystal defect preparation approaches have been applied to enhance the capacitance of bulk materials. However, a comprehensive understanding of active sites in the reaction process is an enigma for all researchers. This work reported an environmentally friendly system with a basic polymerized ferric sulfate (BPFS) electrolyte and electroactive graphite electrode, which achieved high area capacitance and showed the different characteristics of active sites. This enhanced energy storage system shows the evidence that carbon materials are electrochemically activated as a result that active groups could react with iron groups in aqueous solutions. A high area specific capacitance of 12 F cm-2(1255 F g-1) is obtained in a mixed BPFS at 5 mV s-1 in a potential window of 2.1 V in a three-electrode cell. In an aqueous solution capacitor, a capacity of 4.8 F cm-2 at 30 mA from 0 V to 1.5 V is achieved at room temperature. It has the potential to develop a low-cost, high energy storage, and high safety system, which can be a lead-acid battery substitute.