Chelation‐Mediated Aqueous Synthesis of Metal Oxyhydroxide and Oxide Nanostructures: Combination of Ligand‐Controlled Oxidation and Ligand‐Cooperative Morphogenesis

Abstract

We have synthesized nanostructures of iron and cobalt oxyhydroxides and manganese oxides in aqueous solution containing a chelating agent. Nanosheets of FeOOH and NaxMnO2 and nanoflakes of CoOOH were generated from the corresponding divalent metal salts and ethylenediaminetetraacetate (EDTA) by one-pot synthesis under ambient conditions. The chelating agent fulfilled multiple roles in the reaction process and morphogenesis leading to two-dimensional nanostructures. Coordination to the divalent metal ions inhibited rapid precipitation of metal hydroxides and mediated oxidation to tri- and tetravalent species by dissolved oxygen. Along with the deposition, the two-dimensional and single-crystal nanostructures were also associated with interactions of the chelating agent. Therefore, this approach can be regarded as a combination of ligand-controlled oxidation and ligand-cooperative morphogenesis. Parallel control of the reaction and the morphology was achieved by a simple approach. The model cases suggest that tailoring chelation can facilitate the design of other metal oxide nanomaterials.

Flower-like porous hematite nanoarchitectures achieved by complexation–mediated oxidation–hydrolysis reaction

“…As shown in Fig. 1e, the FTIR spectrum of the flower-like nanostructures indicates the main peaks of c-FeOOH (1160 cm À1 , 1022 cm À1 ) [33], which are masked by the strong characteristic peaks of Tris (for instance, 1088 cm À1 , 1078 cm À1 , 1069 cm À1 , 1042 cm À1 , 1037 cm À1 and 1024 cm À1 , according to SDBS information CAS Registry 77-86-1). This seems to imply that the flower-like nanostructures are c-FeOOH but contain some Tris.…”

“…Afterwards, brick-like building blocks randomly aggregate into spheroid-like rudimental nanoparticles by the lowest energy principle. When compressed air is introduced into the reaction system as bubbles, Fe(II) ions in the rudimental nanoparticles are in situ oxidized to Fe(III) ions and then gradually hydrolyze into iron oxyhydroxide [33,36] with simultaneous dissociation of Fe(II)-Tris complexes and release of Tris molecules. As a result, each newly born FeOOH molecules within brick-like building blocks are inclined to migrate and to combine with adjacent ones via hydrogen bonding in order to lower surface energy.…”

Selectively Etching Vanadium Oxide to Modulate Surface Vacancies of Unary Metal–Based Electrocatalysts for High‐Performance Water Oxidation

“…V o can change the energetics of adsorption of H 2 O molecules in the active sites, which is considered to be the rate-determining step for OER. [26,27] It is well-known that amorphous or highly disordered structures are associated with better OER activities as compared to the corresponding highly crystalline counterparts, owing to the presence of more vacancies and exposed catalytically active sites. Without VO y etching, the CoOOH derived from the bare Co (Co 1 V 0 ) by the CV treatment shows a high degree of crystallinity, with a lattice spacing of 0.44 nm (indexed to (003) plane of CoOOH)) with some vacancies/defects, consistent with the FFT pattern which indicates that it is a near-single crystal of CoOOH phase (Figure 6d).…”

Porous Co3O4 Nanosheets with Extraordinarily High Discharge Capacity for Lithium Batteries

“…It is well known that Fe 2 + , Co 2 + , and Mn 2 + could form a tetradentate complex with a N,N'-bidentate ligand, for example, ethylenediaminetetraacetate (EDTA). [22] Here, diacetyldioxime is utilized as a N,N'-bidentate ligand to form a tetradentate complex. A solution of diacetyldioxime has coordination properties that could act as a complexing reagent for Co 2 + ions to form the complex instantly when an aqueous solution of each reactant are mixed together in a beaker.…”