Modeling and Evaluation of a Photoelectrochemical Reactor for H₂ Production

Abstract

A model for the operation of a working photoelectrochemical reactor has been developed and implemented, using the COMSOL Multiphysics TM modeling package. The model incorporates the detailed design of the practical reactor developed to use a 0.01 m 2 Fe 2 O 3 photoelectrode. Initial modeling was used to analyze electrolyte flow within the reactor and recommend modifications to the reactor design. Results indicate that improvements to flow uniformity could be achieved with some minor internal changes. Modeling results confirmed that, under normal operating conditions, bubble formation occurs across the whole photoanode and potentially fills a dead zone in the reactor. The effect of the sheet resistance of the transparent conducting oxide substrate (fluorine-doped tin oxide) on potential and current distribution across the photoanode has also been calculated. This shows that for the 0.01 m 2 photoanode used in this work, potential drop across the photoanode results in large areas of the photoanode becoming inactive to oxygen evolution.

En route to a unified model for photo-electrochemical reactor optimisation. I - Photocurrent and H2 yield predictions

“…19 However, hitherto a model had yet to be developed for photo-electrochemical reactors, in which the photo-absorber and electrode are the same material, coupled with bubble generation at the electrode and the bulk of the electrolyte. Incorporating bubble formation at the photo-electrode|electrolyte interface is important as (i) it enables quantication of the amount of gas produced near the surface and the actual dissolved gas ux diffused into the bulk of the electrolyte that could take part in cross-over losses; 20 (ii) rates of generation of bubbles in photoelectrochemical reactors should be minimised by judicious design, to minimise resistive losses 21,22 and the reection and scattering of incoming light 23 that otherwise would decrease photo-electro-active areas. The latter effect will be addressed in more detail in a subsequent paper.…”