Please clearly formulate your question. Do you mean water electrolysis or "solar thermochemical hydrogen production?" I have a filling that you need  first to learn basics of electrochemistry and chemical thermodynamics. 

thanks for your interest Mr Yurii, really it is both it is an electro-thermochemical cycle for hydrogen production driven by solar energy, my problem is how to model thermodynamiclly the electrolyser

You need to know several parameters: current density versus overpotential, membrane properties, etc. You must well understand basics of electrochemistry  to work on your project

yes sure, thanks a lot