Mitigating voltage losses in photoelectrochemical cell scale-up

In solar water splitting, efforts in scaling up the photoelectrochemical cell beyond laboratory scale have started to attract significant attention. Several large-area devices have been demonstrated, but typically the efficiencies are much lower than their small-area equivalent. Here, two-dimensional finite element modeling is used to evaluate the different sources of voltage loss specifically related to scale-up in solar water splitting devices operated in neutral pH solutions. We quantitatively investigate the influence of the electrode area to these scale-up associated losses (substrate ohmic loss, electrolyte ohmic loss, and local pH-gradient related losses). About 600 mV additional overpotential is needed due to these losses for a cell with electrodes of height of 8 cm at a current density of 10 mA/cm2. We show, however, that by applying engineering and cell design strategies, the voltage losses can be mitigated, resulting in an acceptable ~50 mV overpotential. Overall, this study highlights the additional challenges to be considered in photoelectrochemical cell scale-up and provides strategies to manage and mitigate scaling-related losses.