Synthesis of Nanosheet Crystallites of Ruthenate with an α-NaFeO₂-Related Structure and Its Electrochemical Supercapacitor Property

Abstract

Unilamellar crystallites of conductive ruthenium oxide having a thickness of about 1 nm were obtained via elemental exfoliation of a protonic layered ruthenate, H(0.2)RuO(2).0.5H(2)O, with an alpha-NaFeO(2)-related crystal structure. The obtained RuO(2) nanosheets possessed a well-defined crystalline structure with a hexagonal symmetry, reflecting the crystal structure of the parent material. The restacked RuO(2) nanosheets exhibited a high pseudocapacitance of approximately 700 F g(-1) in an acidic electrolyte, which is almost double the value of the nonexfoliated layered protonated ruthenate.

Dot-Like Formation of Metal Nanocrystals from Exfoliated Ruthenate Nanosheets

“…Their crystallographic thickness cannot be defined accurately at present, as the precise crystal structure of the parent layered potassium ruthenate has still not been resolved. However, combined with the d-spacing of 0.456 nm revealed by XRD analysis of the anhydrous layered protonic ruthenate [12] nanosheets, being composed of a single layer of edge-shared RuO 6 octahedra (∼0.4-0.5 nm thickness), had an average thickness of about 1.3 nm [9]. This apparently larger thickness measured by AFM than the crystallographic thickness can be explained by the presence of adsorbed species, possibly water molecules and charge-compensating protons, on the surface of the anionic nanosheets [16].…”

“…nanosheets [9] gave rise to a topotactic metallization, i.e. transformation from "nanosheet" to "nanosheet", despite the same reduction conditions.…”

“…nanosheets [9] obtained via exfoliation of NaRuO 2 into Ru metal nanosheets [10]. This unusual metallization can be understood as a lowtemperature activation sufficient to release O atoms from the oxide nanosheets without extensive thermal diffusion of the constituent Ru atoms.…”

Preparation and electrode properties of novel redoxable nanosheets of Mn–Ni oxide with and without vacancy defects

“…Various nanosheets with a wide variety of applications have been synthesized, and semiconducting, 1),4) dielectric, 5) electronconducting, 6),7) ion-conducting, 8),9) ferromagnetic, 10),11) photocatalytic, 12), 13) and redoxable nanosheets 4),6), 7) have been realized even just limited to oxide nanosheets.…”

Synthesis of ordered mesoporous ruthenium by lyotropic liquid crystals and its electrochemical conversion to mesoporous ruthenium oxide with high surface area

“…Takai et al have briefly reported on the synthesis of mesoporous Ru black with surface area of 62 m 2 g -1 via lyotropic crystal templating as the end member of the Pt-Ru alloy [23]. In addition to metallic Ru, high surface area ruthenium oxide is also an important material for various applications, including electrocatalysts for chlorine evolution [24], electrochemical capacitor electrodes [25][26][27][28][29], as well as fuel cell electrocatalysts [30][31][32][33][34][35][36][37][38][39]. The small particle size (1-2 nm) and the existence of appreciable pores are important requirements for the high capacitance [40][41][42].…”