The only way is to develop a Aspen custom model because it is a non-conventional unit. There are some examples (for instance also for membranes) in the literature and there are some hints in books dealing with Aspen ONE suite modelling.
There is no existing electrolysis or fuel cell model available in Aspen Plus. You may develop your own models in Aspen Custom Modeler, and then package them up into Aspen Plus if you would like to. Also, subroutine model is also available for you to simulate the user-defined process in Aspen Plus.