Design and Tailoring of the 3D Macroporous Hydrous RuO₂ Hierarchical Architectures with a Hard-Template Method for...

In this work, RuO₂ honeycomb networks (RHCs) and hollow spherical structures (RHSs) were rationally designed and synthesized with modified-SiO₂ as a sacrificial template via two hydrothermal approaches. At a high current density of 20 A g^-1, the two hierarchical porous RuO₂·xH₂O frameworks showed the specific capacitance as high as 628 and 597 F g^-1; this is about 80% and 75% of the capacitance retention of 0.5 A g^-1 for RHCs and RHSs, respectively. Even after 4000 cycles at 5 A g^-1, the RHCs and RHSs can still remain at 86% and 91% of their initial specific capacitances, respectively. These two hierarchical frameworks have a well-defined pathway that benefits for the transmission/diffusion of electrolyte and surface redox reactions. As a result, they exhibit good supercapacitor performance in both acid (H₂SO₄) and alkaline (KOH) electrolytes. As compared to RuO₂ bulk structure and similar RuO₂ counterpart reported in pseudocapacitors, the two hierarchical porous RuO₂·xH₂O frameworks have better energy storage capabilities, high-rate performance, and excellent cycling stability.