Scaled-Up Zero-Gap Photoelectrochemical Device Based on Abundant Materials for Bias-Free Solar Hydrogen Production

Among the green hydrogen production methods, photoelectrochemical (PEC) water splitting integrates light absorption and electrode functionality in single components, offering the perspective of simplicity and cost reduction in future installations. Until now, significant progress has been achieved in terms of understanding and optimizing individual components of PEC systems, such as photoabsorbers, (co)catalysts, and electrolyte formulations. However, integration into a scalable and facile device remains largely unexplored. This work focuses on identifying suitable material combinations that can be integrated into zero-gap PEC reactors. Among the three options, i.e., anion exchange membrane (AEM), bipolar membrane and proton exchange membrane, our analysis suggests AEM-based PEC devices as the appropriate solution for the integration of our (recently) scaled-up BiVO4 photoanodes. This solution allows the use of abundant materials, and it is compatible with strategies for photoanode performance optimization. Our approach includes the evaluation of individual components at a three-electrode setup, their integration within AEM-PEC devices, and evaluation in several operation modes. The most promising AEM-PEC devices were scaled to 100 cm2 using a zero-gap reactor design. This device achieves up to 275 mA and 2.91% solar-to-hydrogen efficiency when coupled with a silicon photovoltaic cell, setting a benchmark for solar water splitting with abundant materials.