Photoelectrode Fabrication and Modular PEC Reactor Integration for Stable Solar Hydrogen Production

Photoelectrochemical (PEC) water splitting is a promising route for solar hydrogen production, yet scalability and environmental safety remain key challenges. Here, we present a modular PEC platform using hematite photoelectrodes fabricated via a scalable polymeric precursor method with uniform Al/Zr comodification to enhance charge transport and adhesion. A total of 100 reproducible photoelectrodes were produced and characterized using customized PEC cells with two different active areas (0.28 and 1 cm2) to assess scale-dependent performance. Ten photoelectrodes were integrated into each 3D-printed reactor, demonstrating an effective small-scale assembly. Ten such reactors could form a 100 cm2 module, supporting scalable deployment. Each reactor delivered stable photocurrents (∼10 mA at 1.23 VRHE) for over 120 h under 1 sun. Outdoor operation of two series-connected reactors reached 20 mA. Ion leaching remained below national discharge limits, confirming environmental safety. This work establishes a scalable, stable, and modular PEC strategy, advancing hematite-based devices toward real-world solar hydrogen production.