Electrodeposition of α‐ and β‐cobalt hydroxide thin films via dilute nitrate solution reduction

Abstract

Abstractα‐ and β‐cobalt hydroxyde thin films were synthesized by cathodic electrodeposition on transparent conductive oxide (TCO) substrates, at 60 °C and 95 °C, respectively, using a very low concentration of Co(NO3)2 and an alkali nitrate supporting electrolyte. Localized cathodic electrochemical generation of hydroxyl species via the reduction of nitrate precursors led to the formation of well crystallized nanostructured films. Scanning Electron Microscopy and X‐ray diffraction confirmed the films were composed of vertically oriented nanoparticle platelets with the c‐axis parallel to the substrate surface, and free of turbostratic disorder. UV/Vis spectra and thermal gravimetric analyses (TGA) indicated variation between the cobalt structures. Films deposited at 60 °C yielded a hydrotalcite‐like compound namely an “hydroxyl‐deficient” [Co(OH)2–x (H2O)x ]x + with NO3– intercalated anion along with water molecules in the interlayer region. Those deposited at 95 °C yielded the brucite β‐Co(OH)2. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Self-assembled hierarchical β-cobalt hydroxide nanostructures on conductive textiles by one-step electrochemical deposition

“…Subsequently, the cobalt (Co 2+ ) ions in the vicinity of the working electrode react with the OH − ions, resulting in the formation of precipitated cobalt hydroxide on the working substrate and providing the subsequent nucleation sites. 21 As shown in Fig. 2(a), the surface of the conductive textile fibers was uniformly covered with thin β-Co(OH) 2 nanosheets at the growth time of 30 min.…”

Modes of Fe Incorporation in Co–Fe (Oxy)hydroxide Oxygen Evolution Electrocatalysts

“…This result suggests the anodically deposited films may contain a larger number of reactive sites where Fe can incorporate and modify the redox properties of the Co cations. This may result from the fact that CV cycling is used deposit the films under anodic conditions (each oxidation cycle leads to deposition of a small amount of CoO x H y ), whereas under cathodic deposition conditions protons are consumed near the electrode surface causing an increase in pH and the precipitation of the CoO x H y …”

Nanostructured α- and β-cobalt hydroxide thin films

“…However, these experiments used the transition metal nitrate salt for dual purposes: as the transition metal ion source and as the supporting electrolyte [8][9][10]. In addition, very little research has occurred using very low concentrations of transition metal salts with alkali nitrates added as a supporting electrolyte for hydroxyl generation [10,28].…”