Review of the structure and the electrochemistry of nickel hydroxides and oxy-hydroxides

Chemical synthesis of α-cobalt hydroxide

“…A third reflection appears at ϳ2.7 Å and exhibits a pronounced asymmetry on the higher angle side. This feature is characteristic of turbostratic materials in which the layers, which are stacked one upon another, are randomly oriented about the principal (c) crystallographic axis [1]. Another reflection of a similar line shape appears at ϳ1.56 Å.…”

“…The distinguishing feature of ␣-nickel hydroxide is its larger interlayer spacing (7.6 Å) compared to that of the ␤-form (4.6 Å), on account of which the ␣-form has a higher electrochemical activity [1] and an interesting interlayer chemistry [5]. There is therefore considerable interest in synthesizing a hydroxide of Co(II) similar in structure and composition to ␣-nickel hydroxide.…”

“…The hydroxides of Ni(II) are known to crystallize in two polymorphic modifications known as ␣ and ␤ [1]. While the ␤-form is a stoichiometric phase of the composition Ni(OH) 2 , the ␣-form is an anion containing the hydroxyl-deficient phase of the composition Ni(OH) 2Ϫx (A nϪ ) x/n ⅐yH 2 O where A nϪ ϭ NO 3 Ϫ , Cl Ϫ , AcO Ϫ , SO 4 2Ϫ , CO 3 2Ϫ ; x ϭ 0.1-0.2 and y ϭ 0.6 -1.0 [2][3][4].…”

Highly Active Mixed-Metal Nanosheet Water Oxidation Catalysts Made by Pulsed-Laser Ablation in Liquids

“…Studies of electrodeposited amorphous α-Ni(OH)2 and its ageing to β-Ni(OH)2 in basic electrolytes suggested that oxygen evolution occurred at lower onset potential for β-Ni(OH)2/β-Ni(O)OH. 18,[21][22][23][24][25][26][27][28] Yachandra and Nocera challenged this notion by correlating structure to activity in a nickel-borate oxygen evolution catalyst. 29 Dai established that crystalline Fe-doped α-Ni(OH)2 on carbon nanotubes is more active than the equivalent β-phase material.…”

“…22,33 Two materials were used in this analysis, (1) almost exclusively Ni(OH)2 and (2) one of mixed (Ni,Fe) composition, due to aging in KOH for 72 hours. The compositions of these materials were determined by XRD and Mössbauer spectroscopy in the original study.…”