Cobalt chromium-layered double hydroxide, α- and β- Co(OH)2 and amorphous Cr(OH)3: synthesis, modification and characterization

Abstract

Cobalt-chromium layered double hydroxide (CoCr LDH), α- and β- Co(OH)2 and amorphous Cr(OH)3 have been synthesized under different reaction conditions. The obtained CoCr LDH was modified by stearic acid (SA) and sodium stearate (SS). The obtained samples have been characterized by X-ray diffraction (XRD), Scanning electron microscope (SEM), Ultraviolet-visible- (UV-Vis), Fourier transform infrared- (FTIR) and Energy-dispersive X-ray- (EDX) spectroscopy. The influence of reaction conditions on product composition, structural and optical properties of the samples have been discussed in detail. The basal spacing of CoCr-LDH increased from 7.366 Å to 7.428 Å and 25.214Å after the intercalation by stearic acid and sodium stearate, respectively. The average particles size by SEM analyze was estimated to be approximately 100–150 nm and 30–50 nm for CoCr-LDH0.6M(90°C) and CoCr-LDH0.6M(90°C)/SS nanostructures, respectively. Mixed hydroxides like α- and β- Co(OH)2 have been obtained along with LDH at lower pH value (pH ∼ 7). The number of diffraction peaks corresponding to β-Co(OH)2 has increased with relatively decreasing of Co2+ ions in the reaction medium. At high chromium concentrations (Co2+:Cr3+ = 1:3 and 1:5), amorphous Cr(OH)3 were formed in the experiment.

Photocatalytic degradation of Ponceau 4R by ZnAl‐layered double hydroxide nanostructures obtained with and without polyvinyl alcohol

“…[ 33 ] Although the particle size decreased with increasing basal spacing, the stability of the layers also weakened as the physical forces between the layers weakened. In the previous study, [ 4 ] the bandgap increased slightly (from 3.5 eV to 3.7 eV) with a sharp intercalation (from 7.366 Å to 25.214 Å). However, in the current study, although intercalation is not so high (from 7.00 Å to 7.62 Å), the bandgap is significantly reduced from 3.23 to 2.87 eV and from 3.25 to 2.82 eV for ZnAl‐LDH (ACTB) and ZnAl‐LDH/PVA, respectively.…”

“…The average value of bandgap energy in LDHs was calculated to be $3-3,5 eV. [3,4] The band gap values indicate the gaps determined for all the semiconductors that exist in the visible-light region; hence, they can be applied in photocatalysis. [5] Zinc containing layered double hydroxides [6][7][8] oxides [9][10][11][12] sulfides [13][14][15] and other semiconductors [16] are very effective photocatalysts with unique optical properties.…”

Synthesis, Properties and Practical Applications of Doped and Undoped, Zinc-Containing Layered Double Hydroxides – A Brief Review

“…pH 9 and 10 are considered optimal for some metals (like Zn, Fe, Ni, Mn, etc.) [20]. Even extremely high concentration alkaline solution is used to obtain LDHs of some metals (like Ba, Ca) [21] because of the ion radii.…”

Facile synthesis approach of bifunctional Co–Ni–Fe oxyhydroxide and spinel oxide composite electrocatalysts from hydroxide and layered double hydroxide composite precursors

“…[31][32][33][34] On the other hand, some studies have reported the formation of metal hydroxides as a byproduct in the synthesis of LDH. 35,36 Therefore, we expect that composite precursors of multi-metal hydroxides and LDHs are synthesized by the precipitation method and that calcination of the precursors at an appropriate temperature yields the composite of metal oxyhydroxide and spinel oxide, providing highly active bifunctional electrocatalysts (Scheme 1).…”