Electrochemical formation of holmium-copper alloys on copper cathode in molten KCl-HoCl_3

Cyclic voltammetry, open circuit potential— time curve after potentiostatic electrolysis and potential step chronoamperometry were used to investigate the electrochemical formation processes of holmium-copper alloys on copper cathode in molten HoCl3-KCl. Intermetallic compounds HoCu5, HoCu4, HoCu2 and HoCu are formed in sequence and then the metallic Ho is deposited when Ho3+ is reduced on copper electrode in molten KCl-HoCl3 at 1066 K. The first charge-transfer reaction is reversible. The structure of holmium-copper alloy film deposited on copper electrode by potentiostatic electrolysis was characterized by X-ray diffraction. The standard free energies of formation for the intermetallic compounds HoCu5, HoCu4, HoCu2 and HoCu are - 95.5, - 92.6, - 73.8 and - 44.0 kJ/mol, respectively. The diffusion coefficient and diffusion activation energy of Ho atom in the alloy are estimated to be 10-10- 10-11 cm2/s and 75.35 kJ/mol, respectively, from the chronoamperometry data.

Cyclic voltammetry, open circuit potential-time curve after potentiostatic electrolysis and potential step chronoamperometry were used to investigate the electrochemical formation processes of holmium-copper alloys on copper cathode in molten HoCl3-KCI. Intermetallic compounds HoCu5, HoCu4, HoCu2 and HoCu are formed in sequence and then the metallic Ho is deposited when Ho^3＋ is reduced on copper electrode in molten KCl-HoCl3 at 1 066 K. The first charge-transfer reaction is reversible. The structure of holmium-copper alloy film deposited on copper electrode by potentiostatic electrolysis was characterized by X-ray diffraction. The standard free energies of formation for the intermetallic compounds HoCu5, HoCu4, HoCu2 and HoCu are -95.5, -92.6, -73.8 and -44.0 kJ/mol, respectively. The diffusion coefficient and diffusion activation energy of Ho atom in the alloy are estimated to be 10^-10-10^-11 cm^2/s and 75.35 kJ/mol, respectively, from the chronoamperometry data.