Controlling Solar Hydrogen Production by Organizing Porphyrins.

In this study, a highly efficient photocatalytic H production system is developed by employing porphyrins as photocatalysts. Palladium and platinum tetracarboxyporphyrins (PdTCP and PtTCP) are adsorbed or coadsorbed onto TiO nanoparticles (NPs), which act as the electron transport medium and as a scaffold that promotes the self-organization of the porphyrinoids. The self-organization of PdTCP and PtTCP, forming H- and J-aggregates, respectively, is the key element for H evolution, as in the absence of TiO NPs no catalytic activity is detected. Notably, J-aggregated PtTCPs are more efficient for H production than H-aggregated PdTCPs. In this approach, a single porphyrin, which self-organizes onto TiO NPs, acts as the light harvester and simultaneously as the catalyst, whereas TiO serves as the electron transport medium. Importantly, the concurrent adsorption of PdTCP and PtTCP onto TiO NPs results in the most efficient catalytic system, giving a turnover number of 22,733 and 30.2 mmol(H ) g(cat) .