Hydrogen sorption kinetics of FeTi alloy with nano-structured surface layers

Abstract

Abstract This paper aims to elucidate the mechanisms of the initial activation of the FeTi alloy with nano-structured surface layers (n-FeTi) by the kinetic measurement of hydrogen absorption of the alloy. The alloy sample was prepared by mechanical grinding. The n-FeTi exhibits much higher initial rate of hydrogen absorption than an untreated FeTi alloy. From the measurements of pressure and temperature dependences of the initial rate of hydrogen absorption, the rate controlling step was found to shift from the dissociation of H 2 molecules on the surface to the permeation of H atoms through grown surface oxide layers with the growth of surface oxide layers. From the measurement of work function, the n-FeTi surface was found to exhibit a much lower value for the work function of 4.73 eV than an untreated surface. These results suggest that the nano-structured surface layers easily exchange electrons with the H 2 molecules, which promote the H 2 dissociation, and hence, results in an enhanced hydrogen absorption rate.