An Integrated 1-Dimensional Model of a Photoelectrochemical Cell for Water Splitting

Abstract

A one-dimensional model of a photoelectrochemical cell for solar water splitting has been developed, with applicability to both “wired” and “wireless” designs. The model of the light absorber handles electron and hole transport. The model of the electrolyte accounts for mass transport through regions of aqueous solution, including stagnant diffusion layers and bulk regions to address mixing due to bubbles, natural convection, or other sources. A polymer membrane may be present in the electrolyte. The models of the light absorber and the electrolyte are integrated through the reactions taking place at the interface between them. Charge transfer from the semiconductor to the solution is handled using a kinetic model involving reactions between the species in both the light absorber and the electrolyte. A simplified model is also presented for use when concentration gradients in the electrolyte are negligible. The simplified model captures the effect of the electrolyte in the boundary conditions for the light absorber. The model is validated against current-potential data for a hydrogen-evolving light absorber with varying degrees of simulated solar illumination. The model then shows how overall solar-to-hydrogen yield depends on the efficiency of the light absorber and the areal fraction of absorbers in a membrane separator.