Synergistic redox enhancement: silver phosphate augmentation for optimizing magnesium copper phosphate in efficient...

The implementation of battery-like electrode materials with complicated hollow structures, large surface areas, and excellent redox properties is an attractive strategy to improve the performance of hybrid supercapacitors. The efficiency of a supercapattery is determined by its energy density, rate capabilities, and electrode reliability. In this study, a magnesium copper phosphate nanocomposite (MgCuPO₄) was synthesized using a hydrothermal technique, and silver phosphate (Ag₃PO₄) was decorated on its surface using a sonochemical technique. Morphological analyses demonstrated that Ag₃PO₄ was closely bound to the surface of amorphous MgCuPO₄. The MgCuPO₄ nanocomposite electrode showed a 1138 C g^-1 capacity at 2 A g^-1 with considerably improved capacity retention of 59% at 3.2 A g^-1. The increased capacity retention was due to the fast movement of electrons and the presence of an excess of active sites for the diffusion of ions from the porous Ag₃PO₄ surface. The MgCuPO₄-Ag₃PO₄//AC supercapattery showed 49.4 W h kg^-1 energy density at 550 W kg^-1 power density and outstanding capacity retention (92% after 5000 cycles). The experimental findings for the oxygen evolution reaction reveal that the initial increase in potential required for MgCuPO₄-Ag₃PO₄ is 142 mV, indicating a clear Tafel slope of 49 mV dec^-1.