Hydrothermal synthesis of manganese phosphate/graphene foam composite for electrochemical supercapacitor applications

Manganese phosphate (Mn-3(PO4)(2) hexagonal micro-rods and (Mn-3(PO4)(2) with different graphene foam (GF) mass loading up to 150 mg were prepared by facile hydrothermal method. The characterization of the as-prepared samples proved the successful synthesis of Mn-3(PO4)(2) hexagonal micro-rods and Mn-3(PO4)(2)/GF composites. It was observed that the specific capacitance of Mn-3(PO4)(2)/GF composites with different GF mass loading increases with mass loading up to 100 mg, and then decreases with increasing mass loading up to 150 mg. The specific capacitance of Mn-3(PO4)(2)/100 mg GF electrode was calculated to be 270 F g(-1) as compared to 41 F g(-1) of the pristine sample at a current density of 0.5 A g(-1) in a three electrode cell configuration using 6 M KOH. Furthermore, the electrochemical performance of the Mn-3(PO4)(2)/100 mg GF electrode was evaluated in a two-electrode asymmetric cell device where Mn-3(PO4)(2)/100 mg GF electrode was used as a positive electrode and activated carbon (AC) from coconut shell as a negative electrode. AC//Mn-3(PO4)(2)/100 mg GF asymmetric cell device was tested within the potential window of 0.0-1.4 V, and showed excellent cycling stability with 96% capacitance retention over 10,000 galvanostatic charge-discharge cycles at a current density of 2 A g(-1). (C) 2017 Elsevier Inc. All rights reserved.