Dynamic Phenomenological Modeling of Pec Cells for Water Splitting Under Outdoor Conditions

A dynamic phenomenological model is proposed for better understanding the underlying mechanisms of photoelectrochemical (PEC) cells for water splitting. The main assumptions of the one-dimensional transient model are (1) that bulk recombination occurs between conduction band electrons and holes in the valence band; (2) that mobile charge transport takes place via diffusion and migration; and (3) that the effects of microscopic electric fields and screening in the cell are negligible. For modeling purposes, the photoanode was assumed to be a homogeneous nanocrystalline hematite structure, with thickness L, porosity ep and tortuosity x. The TCO/semiconductor interface was modeled as an ideal ohmic contact, while the electrolyte/platinised TCO interface was described by the Butler-Volmer equation. The continuity and transport governing equations were defined for the mobile species involved: electrons, holes and hydroxyl ions. The effect of outdoor conditions on the performance of the PEC cells, such as temperature and solar radiation variations during the day and for different seasons of the year, was simulated.