Biomimetic Redox-Mediated Proton Relay in Nanoreactors for Photocatalysis

Mimicking the hierarchical compartmentalization and proton pump machinery of living cells in synthetic nanomaterials offers a promising route for sustainable photocatalysis. Here, we report a hollow CdS@polydopamine nanoreactor that integrates two biomimetic features: (i) A dynamic catechol/o-benzoquinone redox pair in the polydopamine shell that functions as a proton relay (rather than an active pump), accelerating proton-coupled electron transfer (PCET) by reversibly donating and accepting protons, and (ii) compartmentalized nanoreactor architecture comprising a porous shell-defined nanoscale cavity that creates confined microenvironments for mass diffusion, reactant enrichment, and photon trapping. This synergistic integration concurrently promotes both oxygen reduction and water oxidation half-reactions, achieving a record H₂O₂ photosynthesis rate (3.24 mmol g_cat.^-1 h^-1) in aqueous solution under visible-light illumination, with a solar-to-chemical conversion efficiency of 1.2%. The combination of in situ spectroscopy, photochemical analysis, finite element simulations, and theoretical calculations visualizes the biomimetic machinery and elucidates the photocatalytic mechanism. Furthermore, encapsulation within an environmentally benign sodium alginate hydrogel matrix yields monolithic and recyclable photocatalysts capable of stable H₂O₂ synthesis under natural sunlight. This work will inspire a new generation of biomimetic nanomaterials that increasingly replicate the sophistication of living cells, opening frontiers in photosynthesis, energy catalysis, and synthetic chemistry.