Gas diffusion in nanoporous thin films

We analyze the Fick's diffusion of a gas inside porous nanomaterials through the one-dimensional diffusion equation in nanopores for various cases of boundary conditions for homogeneous and non-homogeneous problems. We study the diffusion problems, starting without adsorption of the gas inside the pores, to more complex situations with surface adsorption in the pore walls and at the pore tips. Different methods of solution are reviewed depending on the problem, such as similarity transformation, Laplace transform, separation of variables, Danckwerts method and the Green's functions technique. The recovery step when the diffusion process stops and reached the steady-state is presented as well for the different problems.