Evidence for enhanced catalytic activity of magnesium arising from anodic dissolution

The increasing rate of hydrogen evolving from magnesium (Mg) surfaces under anodic polarization is nowadays well documented and often termed the so-called "negative difference effect" (NDE). Recently, this behavior has been explained by a theory involving an increase in the cathodic exchange current density that arises from the anodic dissolution itself rather than a commonly-mentioned theory involving the formation of univalent Mg and its subsequent chemical reaction with water to produce hydrogen gas. In this work, a series of electrochemical tests were performed to provide evidence in support of the enhanced catalytic surface theory explaining the NDE. Potentiostatic, galvanostatic, and potentiodynamic polarization experiments using high purity Mg electrodes indicated substantial increases in the ability to support the rate of the cathodic reaction following discrete periods of anodic dissolution. (C) 2014 Elsevier Ltd. All rights reserved.