Recent Developments in Photocathodes for Solar-Driven Hydrogen Peroxide Production

Solar-driven photoelectrochemical (PEC) oxygen reduction reaction (ORR) using a photocathode that relies only on oxygen and water offers a promising on-site approach for hydrogen peroxide (H2O2) production. This method provides a sustainable and low-carbon alternative to the energy-intensive anthraquinone process. Both inorganic semiconductors and organic conjugated polymers have been developed as effective photocathode materials for PEC ORR, each with distinct advantages. Inorganic semiconductors generally generate free charge carriers with high mobilities, which leads to improved photocurrent densities. In contrast, organic conjugated polymers exhibit tunable band structures and allow molecular-level incorporation of catalytic sites that favor selective two-electron ORR. This review presents a comprehensive overview of recent advancements in photocathode development for H2O2 generation, focusing on both inorganic semiconductors and organic conjugated polymer-based materials. We emphasize key design strategies, including band structure engineering and active site modulation, to improve charge transfer efficiency and enhance product selectivity. Finally, we discuss the major challenges that currently limit photocathode development and outline emerging opportunities for future innovation. By providing these perspectives, this review seeks to guide the rational design of sustainable H2O2 production systems and contribute to the broader advancement of efficient solar-to-chemical energy conversion.