Supramolecular nanowires solely composed of cobalt and ruthenium salts enable enhanced stability and activity in light-driven hydrogen evolution

Controlling the nanoscale organization of photosensitizer–catalyst (PS–CAT) assemblies into high-surface-area superstructures holds great promise for enhancing photochemical energy conversion yet remains a formidable challenge. We report the nanoconfined deposition of supramolecular photoactive architectures solely composed of cobaloxime-based catalytic salts (CAT) and an imidazophenanthroline-containing ruthenium photosensitizer (PS) salt using via scanning electrochemical cell microscopy (SECCM). This nanoconfinement strategy enables the controlled formation of PS–CAT supramolecular structures ranging from nanospots to nanowires with a diameter of approx. 80–100 nm that catalyze light-driven hydrogen evolution in the absence of covalent linkers. The supramolecular nanowires, formed solely by tuning the nanopipette retraction speed from the surface, exhibit markedly enhanced photoactivity and stability compared to deposited nanospots using the same PS − CAT ratio. Correlative time-of-flight secondary ion mass spectrometry (ToF-SIMS) and nano-infrared (nano-IR) imaging, supported by molecular dynamics simulations, revealed distinct molecular changes of the different nanostructures, highlighting the crucial role of PF₆⁻ − the counterion of the PS − in stabilizing the supramolecular framework. The presented approach allows designing an optimum arrangement of PS − CAT freestanding supramolecular architectures for improved stability and activity without the need for scaffolds and bridging ligands.