A time dependent model to study the effect of surface roughness on reactive–diffusive transport in porous media

A model for reactive–diffusive transport and recycling of hydrogen from rough graphite surfaces is presented which helps understand the qualitative behavior of hydrogen atomic and molecular release as a function of target temperature and incident hydrogen flux, as observed in experiments and simulations. The effect of surface roughness on the reaction rates of atoms diffusing on the surface is presented. We present reasons for some counter–intuitive observations like (i) steady state hydrogen saturation is faster at 600 K than at 900 K, (ii) the steady state hydrogen density on a rough surface is lesser than that for a smooth surface at a specific target temperature and incident hydrogen flux.