A Proof‐of‐Concept Membrane Module Concept for Solar Thermal Water Splitting Using Oxygen Transport Membranes

Solar thermal water splitting using oxygen transport membranes enables sustainable hydrogen production and can thus play a key role in the emerging hydrogen economy. Membrane reactors potentially reduce temperature required by shifting the concentration equilibrium, thereby increasing the efficiency of thermal water splitting. This work presents a scaled‐up proof‐of‐concept (PoC) module design for solar thermal water splitting applications utilizing oxygen transport membranes in relevant environments. The PoC module is based on a flexible and scalable stack design with parallel‐oriented, membrane‐containing layers, which supports the scalability of the concept. Solar heat integration is optimized for direct irradiation by a High Flux Solar Simulator. Key outcomes include focal point adjustments and design modifications using an irradiated copper plate to mitigate hot spots. The PoC module's material concept prevents thermal stresses and ensures gas‐tight sealing of the membranes at an operating temperature of 850 °C under reducing and corrosive atmospheres. Optimal flow rates for steam (30–213 mmol min −1 ) and methane (8–54 mmol min −1 ) are calculated for the PoC module, resulting in efficient hydrogen (7–51 mmol min −1 ) and syngas (22–156 mmol min −1 ) production, using a membrane area of 167 cm 2 , with H 2 O and CH 4 conversion rates of 25% and 95%, respectively.