Abstract
In this paper, results concerning electrochemical deposition of Ni-TiO2 composite coatings are presented. The influence of electrode potential, concentration of TiO2 in the electrolyte, as well as the influence of magnetohydrodynamic effect (MHD) on deposition rate, composition, current efficiency, structure, surface states, and coatings surface morphology is described. Electrochemical studies were preceded by thermodynamic analysis of the system. In addition, the electrokinetic potential (ZP) of TiO2 particles in applied electrolyte was determined. Electrodeposited composites contained up to 2.15 wt. pct of TiO2. Depending on the applied electrolysis conditions, the current efficiency recorded up to 31.7 pct for B = 0 T and up to 34.2 for B = 1 T. Electrochemical studies as well as further material characterizations indicated the strong influence of the magnetic field on processes taking place at the electrode surface. Several results indicated that the synthesis process is accompanied by precipitation of nickel hydroxides and nickel hydrides as well as by hydrogen evolution reaction (HER). The obtained coatings were also characterized in order to determine their photoelectrochemical properties.
Highlights
RESEARCH on the development of new, efficient, and environmentally friendly solar energy conversion systems has been conducted for many years
The changes of cathodic current densities observed in DPV curves as well as the determined diffusion coefficients indicated the significant influence of the magnetic field on the kinetics of transport of species to the electrode surface
The strong effect of the magnetic field on the kinetics of processes accompanying the synthesis of Ni-TiO2 composites was indicated by the quantity of the charge related to the synthesis of coatings under several conditions as well as by the slope of the recorded electrogravimetric curves
Summary
RESEARCH on the development of new, efficient, and environmentally friendly solar energy conversion systems has been conducted for many years. The literature indicates possibilities for modification of the properties of materials synthesized through electrochemical methods by the presence of a magnetohydrodynamic (MHD) effect generated by the Lorentz force, causing an additional convection in the electrolyte. Interaction between disturbed electric field and magnetic field result in generation of Lorentz force which in turn is responsible for magnetohydrodynamic effect (MHD) It can be found in the study of Feng et al that as the result of magnetic field action in near electrode area numerous eddy vortices are located causing additional convection.[31] The presence of the above-mentioned eddy vortices may positively influence the desorption of gas products formed during cathodic electrode polarization from the electrode surface[32] as well as improve dispersion of particles in the volume of the electrolyte. In the literature so far, there are no reports concerning results of electrogravimetric studies under magnetic field, which provide clear evidence of MHD effect on synthesis of Ni-TiO2 coatings
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