Publication
Operation of photoelectrochemical devices at high temperatures can provide a pathway to reduce the operating voltage, increase the production rate, and allow for the use of more earth abundant catalysts. Additionally, high-temperature operation offers the promise to utilize a larger fraction of the solar spectrum through the use of thermal energy and therefore has the potential for higher efficiency operation. However, PEC devices operating at temperatures above 100 °C require the use of new semiconducting junctions for charge separation and ceramic solid electrolytes for ion conduction. The feasibility and design of such devices is not known. We developed a non-isothermal computational model of a high-temperature PEC device, consisting of a photo-enhanced thermionic emitter for photon absorption, charge generation and separation, and a solid oxide electrolyzer for the ionic conduction and the water and CO2 splitting reactions. The model predicted that such a device made of established materials is feasible with operating temperatures of the photoabsorber in the range of 600–800 K, reaching solar-to-fuel efficiencies between 8 to 13%, and H2 evolution rates between 17 to 72 mmol m−2 s−1. It also has the possibility of generating syngas for the generation of synthetic fuels, when the appropriate amount of water is supplied to the device. The device concept was assessed under different scenarios that consider variations in design, operating conditions, and material properties in order to provide general device design guidelines and highlight the potential of high-temperature PEC devices.