Electrochemical noise analysis of the effects of a magnetic field on cathodic hydrogen evolution

The effect of a static magnetic field on the evolution of hydrogen gas from a small platinum electrode in an aqueous electrolyte has been studied by recording the noise spectrum of overpotential voltage fluctuations at a constant current density of -50 mA mm(-2). A 1/f(2) variation of the power spectrum characteristic of droplet coalescence is found for frequencies >10 Hz. The overpotential for hydrogen evolution decreases with applied field. When the production of gas bubbles is quasiperiodic, there is a threshold field of 0.5 T beyond which the size of the bubbles released is approximately doubled. This is explained by enhanced coalescence of small bubbles swept across the electrode surface by forced convection due to the Lorentz force. (C) 2009 Elsevier B.V. All rights reserved.