On the factors enhancing hydrogen trapping in spherical cavities in metals

Using the reaction–diffusion model for hydrogen (H) trapping in spherical cavities in metals (Zibrov and Schmid, 2022), we theoretically analyze the case of H trapping only in chemisorption sites at the cavity surface. We show that the model can be reduced to a form that is similar to the conventional model of H trapping in point defects. The reduced model includes analytical expressions for correction factors to account for correlated H retrapping by the same cavity and inhomogeneous H potential energy landscape in the vicinity of the cavity surface. We show that these correction factors play a significant role in thermal desorption (TDS) simulations only in the case of very low cavity number densities (detrapping-limited regime), which is rarely encountered in experiments.