Electrodeposition of Co-Pd Alloys from Chloride Solutions

A lot of attention has been devoted to synthesis of Co-Pd alloys mainly due to their electrocatalytic properties. Catalytic properties of these alloys for a 4-electron oxygen reduction reaction (ORR) are comparable to the properties of pure platinum. They also demonstrate high resistance to methanol activity, therefore, they can be successfully used in direct methanol fuel cells (DMFC). Significantly lower costs connected with the use of the alloys for electrodes applied in fuel cells in comparison to pure platinum make them an interesting alternative. The alloys play also an important role in magnetic data storage and microelectromechanical systems. The work presents results of the tests over the synthesis of Co-Pd alloys from acid chloride electrolytes. The main aim of the tests was to identify reactions responsible for alloy formation and to determine an influence of the electrolysis parameters i.e. working electrode potential, electrolyte composition and temperature on the composition of the resulted alloy coatings. Electrochemical investigations were performed by applying cyclic voltammetry (CV) combined with Electrochemical Quartz Crystal Microbalance (EQCM). The electrolyte composition was selected based on a thermodynamic analysis and spectrophotometric tests which were described in our previous papers [1, 2]. They allowed determination of equilibrium composition of the metals complex forms and a stability analysis of the electrolyte. The alloys were synthesized within the potentials from - 0.7 V to - 1.1 V. The tests indicate a possibility of alloys synthesis already at the potential range < - 0.5 V.  The alloys composition was analysed with the use of the EDS technique. The obtained alloys featured Pd content from 0.84 to 71.37 at.%.

1. Mech K, Żabiński P, Kowalik R (2013) Co-Reduction of Electrochemically Active [Co(H₂O)₆]²⁺ and [CoCl(H₂O)₅]⁺Complexes onto Gold Electrode. J Electrochem Soc 160 (6):D246 - D250

2. Mech K, Żabiński P, Kowalik R, Fitzner K (2013) Kinetics and Mechanism of [PdCl_x(H2O)_4−x]^2−x (x = 3, 4) Complexes Electro-Reduction. J Electrochem Soc 160 (10):H770-H774