En Route to a Unified Model for Photoelectrochemical Reactor Optimization. II–Geometric Optimization of Perforated Photoelectrodes

Results have been reported previously of a model describing the performance photoelectrochemical reactors, which utilize semiconductor | liquid junctions. This was developed and verified using Sn IV -doped ?-Fe 2 O 3 as photoanodes. Hematite films were fully characterized to obtain parameter inputs predicting photocurrent densities. Thus, measured photocurrents described validated by in terms measurable quantities. The complete reactor model, COMSOL Multiphysics, accounted for gas evolution desorption system. Hydrogen fluxes, charge yields collection efficiencies estimated, revealing critical need geometric optimization minimize H -O product recombination well undesirable spatial distributions current densities “overpotentials” across electrodes. Herein, implemented 3D geometry solid perforated 0.1 × m planar photoanodes an up-scaled dm . same then applied set simulated electrode geometries configurations identify design that would maximize fluxes. modified introducing circular perforations different sizes, relative separations arrangements into otherwise sheet purpose providing ionic shortcuts. We report effects thickness presence or absence membrane separate oxygen hydrogen gases. In incorporating photoanode at 1.51 V vs RHE pH 13.6, optimized flux predicted perforation with separation-to-diameter ratio 4.5 ± 0.5; optimal diameter 50 µm. For reactors without membrane, this 6.5 8.5 “wired” (monopolar) “wireless” (photo-bipolar) design, respectively. results methodologies presented here will serve framework optimize composite photoelectrodes (semiconductor electrolyte), general, production (and oxygen) from water solar energy.