Facile synthesis of MnPO4·H2O nanosheets/MWCNTs composite as electrode material for high-performance supercapacitors

Abstract

We report the fabrication of high stable manganese phosphate (MnPO₄·H₂O) nanosheets MnPO₄·H₂O/MWCNTs nanocomposites by a one-step facile hydrothermal synthesis followed by an annealing process. XRD results confirm that pure and composites show a monoclinic structure with a space group of C₂/c (Z = 4). SEM and TEM images reveal that the disordered structure made of nanosheets with a lateral dimension of 100–150 nm and a thickness of ca. 10-15 nm can be observed in pristine MnPO₄·H₂O. Raman spectra again prove that monoclinic phases of MnPO₄·H₂O and presence of MWCNTs in the MnPO₄·H₂O/MWCNTs composite. The Pore Size and Surface distribution are studied through BET analysis, and the results show that the MnPO₄·H₂O/MWCNTs composite shows highest specific area (135 m² g⁻¹) and lower pore size 7.8 nm (compared to pristine MnPO₄·H₂O). The XPS result reveals that Mn is 2⁺ in a state in the spinel MnPO₄·H₂O. The MnPO₄·H₂O/MWCNTs composite delivers the capacity of about 765 F g⁻¹ at a specific current of 2 A g⁻¹ and capacity retention of about 94% after 5000 cycles. This study opens a new window for the fabrication of phosphate based materials for supercapacitors applications.