Magnetic field-controlled bubble templated CuNi foam films and their performance towards hydrogen evolution reaction in alkaline media

CuNi alloys constitute a promising alternative to noble metals as hydrogen evolution reaction (HER) electrocatalysts, owing to their low cost, high corrosion resistance and environment friendly properties. In this study, homogeneous magnetic fields applied during hydrogen bubble template-assisted electrodeposition of CuNi foam films are shown to have an effect on the resulting morphology and chemical composition of the foam films. The reason for this is the interplay between the applied current density and the orientation of magnetic fields, both influencing the Lorentz forces acting during the growth of the films. With upward Lorentz force, both the pore size and the relative Ni content decrease within the window of studied current densities (−0.7 to −3.5 A cm−2) compared to deposits grown under downward Lorentz force or no applied field. The electrochemical activity towards HER in alkaline media of the CuNi foam films deposited under upward Lorentz force have been investigated by polarization tests, chronopotentiometry and electrochemical impedance spectroscopy. The CuNi foam film with 36 at.% Ni exhibits the highest HER activity, and the overpotential required to reach a HER activity of −10 mA cm−2 is as low as −38 mV vs. reversible hydrogen electrode (RHE).