Structure of the Electrodeposits Obtained from Alkaline Solutions Containing MoOr42- Ions

Molybdenum oxygen-containing solid-phase compounds were electrodeposited on the platinum cathode from the alkaline solutions containing sodium molybdate or ammonium molybdate under galvanostatic condition.Bath composition and electrolytic condition were as follows:Sodium bath: Na2MoO4·E2H2O (0.2M), NaOH (for adjusting pH10.5)Ammonium bath:(NH4) 6Mo7O24·E4H2O (0.2M as Mo), NH4OH (for adjusting pH10.5)Current density: 50mA/cm2, Temperature: 70°CBlack deposits were obtained from the sodium baths and black-brown deposits from the ammonium baths.Structure of these deposits were investigated by studying the crystallization processes of the deposits. Thermal analysis curves, X-ray diffraction pattern, infra-red absorption spectra measurements and trymethyl-silylation of the deposits were carried out and following results were obtained.As plated state, deposits were amorphous MoO2-n (OH) 2n (n; 0-2). Deposits obtained from the sodium bath contained Mo6+and Na+. Deposits were dehydrated to crystallize as MoO2, Na2Mo3O6.5 and small amount of Na2MoO4 with elevating temperature.Deposits obtained from the ammonium bath contained NH4. Differing from the deposits obtained from the sodium bath, they scarcely contained Mo6+. Deposits dehydrated with vapouring NH3 to crystallize as MoO2 by elevating temperature.