Simultaneous inner and outer modification of Mg-doped NiCoP nanoflowers anchored on graphene hydrogel for high performance supercapacitor cathode

Artikel i vetenskaplig tidskrift, 2026

The simultaneous enhancement of capacity, rate capability, and cycling stability is crucial for developing supercapacitor electrode material. In this work, Mg-doped NiCoP nanoflowers (MNCP) grown on graphene hydrogel (MNCP-GH) are fabricated on a Ni foam substrate (MNCP-GH/NF). The MNCP-GH/NF electrode offers abundant active sites, good conductivity, and structural stability. As a Lewis acid, the Mg ion can modulate the electron distribution around NiCoP, thereby raising the oxidation state of the active metal centers and further increasing the number of redox-active sites. GH with hierarchical pores and a large surface area endows a high MNCP-GH loading of 8.0 mg cm⁻². In addition, the conductive GH skeleton not only acts as a robust and conductive support for immobilizing MNCP nanoflowers but also establishes an interconnected electron transport pathway and facilitates rapid ion diffusion. Consequently, the MNCP-GH/NF electrode achieves excellent areal and mass-specific capacities of 10,560 mC cm⁻² and 1320 C g⁻¹ at 2 mA cm⁻². Remarkably, an excellent capacity retention of 73.2% at 100 mA cm⁻² exhibits its outstanding rate performance. The assembled solid-state MNCP-GH/NF||polyvinyl alcohol-potassium hydroxide (PVA-KOH)||GH/NF supercapacitor delivers an energy density of 53.7 Wh kg⁻¹ (4.3 mWh cm⁻³) and a power density of 18,749 W kg⁻¹ (1499 mW cm⁻³). Moreover, the assembled device also maintains 85.7% of its original capacitance after 10,000 cycles. It is a promising and versatile strategy for designing bifunctional cathodes toward long-term stability and high energy storage.