Hydrogen Absorption Mechanism into Iron in Aqueous Solution Including Metal Cations by Laser Ablation Tests and First-principles Calculations

Abstract

In order to clarify the effect of metal cations (Zn²⁺, Mg²⁺, Na⁺) in aqueous solution on hydrogen absorption into iron, the amount of hydrogen absorption from iron surface was measured by electrochemical tests with a laser ablation. Moreover, in order to obtain the basic mechanism of hydrogen absorption with adsorption of metal cation, we obtained the adsorption potential of the adsorbed atom and the electronic state around the adsorbed atom using first principles calculations. Peak value of permeation current and the time until the current reached the peak value decreased and elongated in the order of NaCl, MgCl₂, and ZnCl₂ solutions. Also, by first-principles calculations adsorption strength of each metal atom increased in the order of Na < Mg < Zn. It was suggested that dissolution of Fe is inhibited due to formation of dense metal layer in the solution including the metal cation which has large adsorption strength to Fe surface like Zn, and finally permeation current may have been reduced.