Hollow MO x -RuO2 (M = Co, Cu, Fe, Ni, CuNi) nanostructures as highly efficient electrodes for supercapacitors

Abstract

Engineering the internal structure and chemical composition of nanomaterials in a cost-effective way has been challenging, especially for enhancing their performance for a given application. Herein, we report a general strategy to fabricate hollow nanostructures of ruthenium-based binary or ternary oxides via a galvanic replacement process together with a subsequent thermal treatment. In particular, the as-prepared NiO-RuO2 hollow nanostructures loaded on carbon nanotubes (hNiO-RuO2/CNT) with RuO2 mass ratio at 19.6% for a supercapacitor adopting the KOH electrolyte exhibit high specific capacitances of 740 F g −1 at a constant current density of 1 A g −1 with good cycle stability. The specific capacitance for hNiO-RuO2/CNT electrodes maintains 638.4 F g −1 at a current density of 5 A g −1 . This simple approach may shed some light on the way for making a wide range of metal oxides with tunable nanostructures and compositions for a variety of applications.

Functionalization of Hollow Nanomaterials for Catalytic Applications: Nanoreactor Construction

“…Owing to the easy‐to‐manipulate microstructure and delimited local voids, researchers recently have demonstrated that elaborated hollow nano/microstructures exhibit superior performance as the primary materials in a variety of emerging research fields, such as catalysis, lithium‐ion batteries (LIBs), supercapacitors, proton‐exchange‐membrane fuel cells (PEMFCs), chemical sensors, and biomedicine . Along with tremendous progress on microstructural characterizations and basic growth mechanism of nanocrystals, hollow nanomaterials become one of the hot spots in the modern research of nanoscience, particularly focusing on the development of synthetic methodologies and structure‐correlated properties …”

Understanding of the major reactions in solution synthesis of functional nanomaterials

“…It should be pointed out that, in addition to hollow binary nanoboxes and oxide nanostructures, galvanic replacement could also be applied to generate hollow nanotubes [329,350,351], nanocages [352][353][354], multiple-walled nanoshell [355] and so on. Most recently, Yang and co-workers [356] reported the galvanic replacement of Ru and a set of transition metals such as Co, Cu, Fe and Ni to fabricate hollow nanostructures. Moreover, after a simple thermal treatment in air, the bimetallic structures can be in-situ transformed into the hollow metal oxides structures without changing their symmetry.…”

Hierarchically nanostructured transition metal oxides for supercapacitors

“…As a new energy storage approach, SCs combine the advantages of high energy density of rechargeable batteries and high power density of dielectric capacitors [19][20][21][22][23][24][25][26][27][28][29]. SCs have been regarded as highly important candidates for energy storage devices because of their fast charging-discharging capability, long cycle stability (>10 5 cycles), high power density (>10 kW kg −1 ), low cost, environment-friendly nature, low maintenance, and safe operation [30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46]. In certain fields, SCs can partly or fully replace traditional batteries.…”