Surface effects on the kinetics of hydrogen absorption by metals

Abstract

We have studied a straightforward model for the kinetics of solution of hydrogen in transition metals which includes an explicit coupling between the surface and the bulk. In constrast to previous work we find that for this process there is no rate-limiting step per se; rather the rate equations for the two steps must be solved simultaneously. In addition, we note that for all known metals the desorption energy is larger than the solution energy (i.e., surface hydrogens are more tightly bound than bulk hydrogens). This leads to an inherent reduction in the rate of filling over the ideal rate.