Photoelectrochemical H2O2 production and organic synthesis: from independent routes to synergistic integration.

Photoelectrochemical (PEC) systems offer a sustainable route for converting solar energy into high-value chemicals beyond conventional water splitting. However, the practical viability of conventional PEC water splitting is constrained by sluggish oxygen evolution kinetics, thermodynamically demanding energy profiles, and charge recombination, bottlenecks that have motivated the search for alternative anodic reactions. This review centers on two promising substitutions for water oxidation including PEC H2O2 generation and organic molecular transformations, which can circumvent the aforementioned limitations by enabling more favorable reaction thermodynamics and kinetics. We first summarize the independent developments in PEC H2O2 production and organic synthesis, detailing their fundamental reaction mechanisms, photoelectrode optimization strategies, and diverse reactor architectures. We then examine their emerging integration, with particular emphasis on in situ PEC H2O2 generation coupled with organic oxidation, which provides opportunities for improved charge utilization and diversified PEC synthesis pathways. Despite these advances, significant challenges remain, including interfacial regulation, long-term catalyst stability, practical operating conditions, and scalable reactor fabrication, which we elaborate alongside corresponding future research opportunities. This review aims to provide a unified perspective on the development and integration of PEC H2O2 production and organic synthesis toward sustainable solar-to-chemical conversion.