Fossil fuels that are widely used today have problems such as carbon dioxide emission that causes global warming due to their combustion, and limited resources. To solve these problems, it is indispensable to use clean energy that does not emit carbon dioxide, or to use renewable energy sources.
Against this backdrop, our laboratory is working on research with the aim of building an artificial photosynthesis system that mimics photosynthesis that occurs in nature and converts solar energy, an inexhaustible resource, into chemical energy. We believe that this will eliminate the current energy problem and create a sustainable energy society.
The artificial photosynthesis system we aim for can be divided into a photohydrogen generation system through the complete decomposition of water and a carbon dioxide reduction system to obtain useful carbon resources. Since hydrogen produces only water during the energy conversion process, it is a very good renewable energy.
One of our goals is to realize a carbon-recycling society where useful resources are generated by carbon dioxide reduction and reused as energy. Since the visible light that accounts for the majority of sunlight cannot exceed the activation energy of the hydrogen generation reaction and carbon dioxide reduction reaction, those reactions do not proceed with sunlight. Therefore, the activation energy is reduced by a catalyst made of a metal complex to accelerate the reaction.
A metal complex is a generic name for molecules called ions and ligands centered on metal ions, and compounds that are formed by coordination with the metal ions. Since various molecular designs are possible by changing the central metal ion and ligand, various functions can be provided.
A typical result of our laboratory is a single-molecule photohydrogen production catalyst that combines a ruthenium complex that absorbs light and a platinum complex that is an excellent hydrogen production catalyst. As a result, the hydrogen generation reaction that previously required multiple components can now proceed with this single molecule.