Enhanced supercapacitor performance with hierarchically porous SnO₂ embedded in reduced graphene oxide nanosheets

This study presents hierarchically porous SnO₂ microspheres embedded in reduced graphene oxide (SnO₂/rGO-T) as high-performance supercapacitor electrodes. Synthesized via hydrothermal treatment with fluoride ions and annealing (300 °C/500 °C), the SnO₂/rGO-T structure leverages Ostwald ripening and high-energy crystal facets to optimize porosity and ion diffusion. Fluoride ions guide SnO₂ growth on ultrathin rGO nanosheets, forming uniform microspheres with enhanced conductivity. Annealing at 500 °C yields superior crystallinity and hierarchical structure, enabling SnO₂/rGO-500 to achieve a specific capacitance of 241 F/g (2 M KOH), energy density of 22.7 Wh/kg, and power density of 900 W/kg at 1 A/g, with 89.7 % capacitance retention after 10,000 cycles—outperforming SnO₂/rGO-300 and bare SnO₂. The synergy between rGO (preventing aggregation) and annealed SnO₂ (improving charge transfer) underpins this performance. This work offers a scalable, rational design strategy for SnO₂-rGO electrodes in energy storage applications.