Revealing the electrochemical performance of a manganese phosphite/RGO hybrid in acidic media.

Transition metal phosphorous-based materials are considered as an ideal candidate for energy storage due to their robustness and durability. In this report, we present manganese phosphite, Mn 11 (HPO 3 ) 8 (OH) 6 , an interesting inorganic material with spectacular structural features. A single step hydrothermal synthetic route was employed for the fabrication of a series of manganese phosphite/RGO hybrids (Mn-HPO/RGO-5, Mn-HPO/RGO-10, Mn-HPO/RGO-20). The as-synthesized hybrid (Mn-HPO/RGO-10) delivers a specific capacitance of 770 F g -1 when operated at 1 A g -1 current density in a three-electrode set-up with a rate capability of 66%. To broaden the practical applicability of the Mn-HPO/RGO-10 hybrid, an asymmetric supercapacitor (ASC) device was fabricated with MXene (Ti 3 C 2 ) as a negative electroactive material and a Mn-HPO/RGO-10 hybrid as a positive active material. The as-fabricated device projects a specific capacitance of 108 F g -1 with an energy density of 34 W h kg -1 along with a power density of 508 W kg -1 . Moreover, the ASC device retains a specific capacitance of 94% after 12 000 constant charge and discharge cycles, suggesting the excellent durability of the ASC device. These systematic investigations illustrate the potential of the Mn-HPO/RGO-10 hybrid as a high-performance energy storage device.