|The supramolecular system for photocatalytic H2 production uses Ruthenium (left) as the photosensistizer and cobaloxime catalytic centers (right). Click to enlarge.|
Researchers at the joint Laboratoire de Chimie et Biologie des Métaux (LCBM), CEA-CNRS-Université Joseph Fourier, have developed a new supramolecular system for the photocatalytic production of hydrogen that uses a cobalt-based catalyst rather than a noble metal catalyst. They reported on their work in the 4 January issue of the journal Angewandte Chemie International Edition.
In researching the redirection of photosynthesis for hydrogen production, scientists have developed molecular systems capable of both photosensitization, which captures light energy, and catalysis, which uses the energy collected to liberate hydrogen from water. To date, according to the LCBM team, all such systems developed to produce or use hydrogen rely on noble metals such as platinum for catalysts.
Current research focuses on developing alternative catalysts based on metals which are naturally more abundant and less expensive, such as those used by natural organisms (iron, nickel, cobalt, manganese).
The new supramolecular system developed by the LCBM researchers functions as both the light-harvesting photosensitizer and the catalyst. Hydrogen production is catalyzed by various cobaloxime centers with greater efficiency than comparable systems using noble metals (Pd, Rh and Pt), according to their results. The catalyst stability, CoII/CoI redox potential, and nucleophilicity of the cobaloxime moiety all affect the photocatalytic properties.
The system still uses Ruthenium as the photosensitizer; one of the next steps in this work will be finding an alternative.
While the ultimate goal is still to use water as a proton and electron source (to avoid adding an organic molecule), this outcome represents considerable progress towards the photoproduction of hydrogen, according to the team.
Aziz Fihri et. al. Cobaloxime-Based Photocatalytic Devices for Hydrogen Production. Angewandte Chemie International Edition, Volume 47, Issue 3, Pages 564 - 567