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(HPO)(OH), 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 when operated at 1 A g 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 (TiC) 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 with an energy density of 34 W h kg along with a power density of 508 W kg. 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.