Modification of electrodeposited cobalt alloys for hydrogen evolution by superimposed external magnetic field
|Gabriel Fryc , Marcin Górski , Remigiusz Kowalik , Piotr Zabinski|
AGH University of Science and Technology (AGH), al. Mickiewicza 30, Kraków 30-059, Poland
The electrocatalytic activity towards the hydrogen evolution reaction is most likely related to the active surface area of the coatings (accounting for the porosity of the coatings and the presence of some nodules at the coatings surface). It is known that magnetic field (B) influence the electrodeposition process of metals. The different magnetic force generates an additional convection, which can affect the morphology of the deposit.
In principle, the grain size is a function of the nucleation rate and the growth of the nuclei: the more the nuclei the smaller is the resulting grain size. It is known that the nucleation rate increases with decreasing nucleation work. Magnetic field applied parallel to the electrode generates an additional convection in the electrolyte caused by the Lorentz force, which acts on the ions. A laminar flow of ions in the electrolyte close to the electrode surface takes place. The magneto hydrodynamic effect (MHD) reduces the thickness of the diffusion layer and leads to an increasing concentration gradient, which should have an effect on the grain size. Superimposed B can influence the texture and the phase formation of electrodeposits. This can be explained by two different effects: Firstly, the layer growth can be influenced directly by B, if B induces a grain growth in the direction of the easiest magnetization. Secondly, the whole electrodeposition process is influenced by the additional convection.
The work aims to obtain Co-W and Co-P alloys by electrodeposition having high cathodic activity for hydrogen evolution in 8 M NaOH at 90°C. External magnetic field generated by permanent magnet was used in order to modify composition and morphology of alloy. The changes in morphology and composition of alloys was searched in order to determine influence of magnetic field on alloys` electrodeposition.
The authors express their acknowledgment to Polish Ministry of Education and Science for financial support under grant No. 3 T08B 016 29.
Presentation: Oral at E-MRS Fall Meeting 2007, Symposium D, by Piotr Zabinski
See On-line Journal of E-MRS Fall Meeting 2007
Submitted: 2007-04-16 12:31 Revised: 2009-06-07 00:44