Self-assembled three-dimensional hierarchical graphene hybrid hydrogels with ultrathin β-MnO2 nanobelts for high performance supercapacitors

Abstract

We report a facile method to assemble a hierarchical and interconnected reduced graphene oxide/β-MnO₂ (rGO/β-MnO₂) nanobelt hybrid hydrogel by dispersion of presynthesized ultrathin β-MnO₂ nanobelts (NBs) in graphene oxide (GO) precursor solution by a hydrothermal reaction. The microscopic structure of the three-dimensional (3D) hybrid hydrogel can be controlled by adjusting the content of the ultrathin β-MnO₂ NBs, which exhibits the properties of low density, large specific surface area, and high compressive strength for the corresponding aerogel. Importantly, a typical hybrid hydrogel with 54.2% ultrathin β-MnO₂ NBs displays a specific capacitance as high as 362 F g⁻¹ at a current density of 1.0 A g⁻¹, and even 282 F g⁻¹ at 20 A g⁻¹, which is three times higher than that of the pure rGO hydrogel (118 F g⁻¹). Meanwhile, the typical hybrid hydrogel also shows outstanding cycling stability with 96.3% capacitance retention after 10 000 cycles of cyclic voltammetry (CV) scans. These findings open up the use of ultrathin NBs for the self-assembly of hybrid hydrogels as high performance supercapacitor devices in energy storage and conversion.