A photo-catalytic water-splitting is attracting attention as the most clean and affordable method to produce hydrogen gas, a sustainable and clean energy source. Until now, dye sensitized inorganic semiconductors such as TiO<sub>2</sub> or ZnO<sub>2</sub> have been mainly explored as photo-catalytic templates, which are however limited by their insufficient performance and compatibility in water, high manufacturing cost, and the difficulty in the fine tuning of band structures. Therefore, in order to realize industrialization, it is demanded to develop innovative new materials. While many efforts have been and are being devoted in this field, relatively new studies using organic materials are particularly noticeable. Because of its unlimited structural design capacity, organic molecules are being actively investigated for many different opto-electronic applications including photcatalyst. Push-pull type donor-acceptor structure in the conjugated molecular skeleton provides an essential driving force for charge separation and a visible light absorption. While some pioneering works using donor-acceptor type polymers or covalent organic frameworks (COFs) are recently being reported, their photocatalytic performance and stability are yet to be improved significantly. In this study, we explored entirely different class of all organic photosensitizer templates which are easily fabricated by the self-assembly process of water-soluble aromatic small molecules comprising donor-linker-acceptor moieties. These donor-acceptor type molecules were self-assembled into nano-particles of 10 nm ~ 200 nm size range depending on their chemical structures and concentration. These organic nanoparticles were well-dispersed in pure water, and were stable upon high-intensity visible light radiation. We evaluated hydrogen evolving photocatalytic performance of them in water by employing the same moles of platinum with the photosensitizer molecule as a co-catalyst and excess amounts of L-ascorbic acid as a sacrificial reagent. It was observed by TEM that the metallic platinum nanoparticles were successfully hybridized on this all-organic self-assembled nanotemplate. Impressively, this hybrid organic photocatalyst system showed hydrogen evolution reaction (HER) turnover number (TON) of 4,000 in pure aqueous solution by visible light radiation of 300 W Xenon lamp.

Highly efficient all organic supramolecular nanotemplates for visible light driven hydrogen evolution from water

256th National Meeting (2018)

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