MotW09 – Catalytic Decomposition of Water

The molecule of the week comes from ongoing research by Dr. Randolf Thummel at the University of Houston (Zeping Deng, Huan-Wei Tseng, Ruifa Zong, Dong Wang, and Randolph Thummel. Inorg. Chem. 2008, 47, 1835 – 1848).  The article focuses on research done in the catalytic decomposition of water into hydrogen and oxygen using diruthenium complexes.  One of the major hurdles which must be overcome in order for hydrogen is the large scale production of hydrogen in an environmentally friedly way.  Currently, hydrogen is produced from hydrocarbons or through the electrolysis of water.  Using hydrocarbons does not solve the problems of oil dependency and using electrolysis requires large amounts of electricity, which would likely be produed by burning coal.  The ultimate goal of the Thummel group is to produce a photocatalyst which will use UV- light to carry out the redox reaction converting water into hydrogen gas and oxgyen gas. The ability to catalyze the decomposition of water is partly due to the presence of the two ruthenium centers so close to one another.  A molecule of water binds to each metal center and hydrogen is release through an oxidation process.  The oxgyen atoms are then within close enough proximity to react to form diatomic oxygen.  Currently, the diruthenium complex is able to catalyse the decomposition of water only in a highly acidic (pH=1) solution in the presence of Ce(IV).  The role of the Ce(IV) is as a sacrificial oxidant.  Future research by the Thummel group will focus on further understanding the specific mechanism involved in the catalysis reaction with the eventual goal of using UV-light to drive the reaction.

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