Selective and Controlled Synthesis of α- and β-Cobalt Hydroxides in Highly Developed Hexagonal Platelets

Abstract

We report on the controlled synthesis of single-crystal platelets of alpha- and beta-Co(OH)2 via homogeneous precipitation using hexamethylenetetramine as a hydrolysis agent. The alpha- and beta-Co(OH)2 hexagonal platelets of several micrometers in width and about 15 nm in thickness were reproducibly yielded in rather dilute CoCl2 solutions in the presence and absence of NaCl at 90 degrees C, respectively. The phase and size control of the products were achieved by varying both CoCl2 and NaCl concentrations. Polarized optical microscope observations revealed clear liquid crystallinity of colloidal suspensions of these high aspect-ratio platelets. The as-prepared alpha-Co(OH)2 containing interlayer chloride ions was intercalated with various inorganic or organic anions, keeping its high crystallinity and hexagonal platelike morphology.

Effect of surface morphology on atmospheric corrosion behaviour of Fe-based metallic glass, Fe67Co18Si14B1

“…SEM micrographs from rusted region on the wheel side showed spherical and faceted morphology of rust constituents (figure 8). The morphology of rust matches with the morphology of goethite, lepidocrocite, magnetite and cobalt hydroxide phases (Cornell and Schwertmann 2003;Liu et al 2005). The magnetite phase possesses spherical, goethite and lepidocrocite faceted type and cobalt hydroxide possesses hexagonal plate like morphology.…”

Electrochemical Water Oxidation Catalyzed by an In Situ Generated α‐Co(OH)2 Film on Zeolite‐Y Surface

“…This higher activity of a-Co(OH) 2 in comparison to bCo(OH) 2 stems from its unique layered structure with positively chargedC o(OH) 2Àx layers and charge-balancing interlayer anionss uch as NO 3 À ,C l À ,o rO H À . [41] These interlayer anions are probablyr esponsible for the higher electrochemical activity of a-Co(OH) 2 compared to its b-isomer,a ss hown previously.T o understand the kinetics of the oxygen evolution reactionu sing Y-a-Co(OH) 2 as an electrocatalyst, galvanostaticp olarization was performed in 0.1 m KOH (pH 13). Figure 6s hows the representativeT afel plots for aY -a-Co(OH) 2 -modified glassy carbon electrode under steady-state mass-transfer control.…”

Anion mediated polytype selectivity among the basic salts of Co(II)

“…The resulting compound has x ¼ 0:22 which is much less than the typical values (0.5-1.0) seen in basic salts. This hydroxyl-rich composition is associated with the a-hydroxides [32,33]. The a-hydroxides are obtained by the protonation of a fraction, x, of the hydroxyl ions.…”