Enhancing the performance of hybrid supercapacitor and oxygen evolution reaction via temperature-modulated binder-free (zinc strontium phosphate/nitrogen-graphene quantum dots) electrode

Utilizing a straightforward hydrothermal methodology, we synthesized an electrode material, zinc strontium phosphate doped with nitrogen-induced graphene quantum dots (ZnSrPO₄/N-GQDs). The Brunauer–Emmett–Teller (BET) measurements unveiled an impressive surface area of 138.025 m²/g, highlighting the material’s favorable characteristics for energy storage applications. By elevating the electrolyte temperature to 80 °C during the electrochemical process, we achieved a substantial augmentation in specific capacity, culminating in an exceptional 1764 C/g at a 1.0 A/g current density. The asymmetric design of the ZnSrPO₄/N-GQDs (80 °C)//Activated carbon (AC) configuration exhibited remarkable power and energy density, encompassing a broader potential window of 1.6 eV. This design delivered a power density of 1500 W/kg alongside an energy density of 56.68 Wh/kg, highlighting that it is suitable for advanced energy storage systems. Impressively, the material exhibited exceptional cyclic stability, retaining 94% of its initial capacity after enduring 10,000 charge–discharge cycles. Through comprehensive numerical analysis, we elucidated the capacitive and diffusive contributions within the asymmetric device. In its role as an oxygen evolution reaction (OER) catalyst, the ZnSrPO₄/N-GQDs (80 °C) electrode demonstrated outstanding electrocatalytic properties displaying a Tafel slope of roughly 63 mV/decade and a minimal overpotential of 160 mV at a current density of 10 mA/cm⁻². This research serves as a significant advancement, providing a versatile platform for harnessing phosphate materials to optimize the performance of energy storage devices. It not only enhances the prospects for hybrid supercapacitors but also augments the Oxygen Evolution Reaction (OER), thus holding immense promise for a wide array of energy-related applications.