Redox activity of selenocyanate anion in electrochemical capacitor application

In this work, we report on the performance of carbon-based electrochemical capacitors operating in an aqueous solution of potassium selenocyanate (KSeCN) as redox active electrolyte, applied for capacitance and energy enhancement. The source of faradaic contribution is pseudohalide anion, SeCN−, demonstrating reversible redox reaction on the positive electrode. Since the standard potential of SeCN–/(SeCN)2/(SeCN)3– is close to the I–/I2/I3– redox couple, the capacitor demonstrates similar hybrid operation. With cost-effective stainless steel (SSt) current collectors, the system displays high capacitance 43 F·g−1 (0.5 A·g−1) and performs at 1.4 V (1 A·g−1) for 9 000 cycles with 90% capacitance retention.