Bias-Free Photoelectrochemical System for Scalable Solar-Driven Hydrogen Peroxide Production via Molecularly Engineered Conjugated Polycarbazole Frameworks.

Solar-driven photoelectrochemical (PEC) synthesis emerges as a promising pathway to produce hydrogen peroxide (H2O2), reimagining the energy-intensive anthraquinone method. However, scaling PEC systems from laboratory-scale prototypes to practical large-area installations remains a significant scientific and engineering challenge, primarily due to limited catalytic selectivity at photoelectrode surfaces and rapid performance degradation during upscaling. This study presents a modular, bias-free PEC system designed for scalable solar-driven H2O2 production. Conjugated polycarbazole frameworks (CPFs) containing rationally designed diacetylene and anthraquinone moieties functions as molecularly precise catalytic layers, enabling concurrent two-electron pathways at both the photoanode and photocathode. The resulting photoanode and photocathode deliver faradaic efficiencies of 94.08% and 95.50%, respectively, for H2O2 production. Integrating these photoelectrodes into a 1 cm2 unbiased tandem PEC device achieves a solar-to-chemical conversion (SCC) efficiency of 2.11%. More importantly, scaling these devices to a 1 m2 membrane-free PEC panel reactor via a modular assembly strategy yields an average SCC efficiency of 1.10% under natural sunlight, representing the largest reported solar-driven PEC system for H2O2 production to date. This study bridges the gap between laboratory-scale experimentation and real-world applications, providing a scalable framework for decentralized, solar-driven H2O2 production.