Electrochemical synthesis of alpha-cobalt hydroxide

Cathodic reduction of an aqueous solution of cobalt nitrate at low pH, high Co(II) ion concentration (greater than or equal to 1 M) and low current de nsities (< 0.3 mA cm(-2)) leads to the formation of a novel layered hydroxi de of Co(II) with an interlayer spacing of 8.93 Angstrom. This hydroxy defi cient phase is structurally and compositionally related to alpha-nickel hyd roxide, but likely contains Co(II) ions in a mixed octahedral/tetrahedral c oordination. Under other deposition conditions, the better known beta-cobal t hydroxide (a=3.17+/-0.01 Angstrom, c=4.61 +/- 0.02 Angstrom) is obtained.