Concerted O atom-proton transfer in the O—O bond forming step in water oxidation

Journal Article · Tue Apr 20 00:00:00 EDT 2010 · Proc. Natl. Acad. Sci. USA

DOI:https://doi.org/10.1073/pnas.1001132107· OSTI ID:1064658

Chen, Zuofeng ^[1]; Concepcion, Javier C. ^[1]; Hu, Xiangqian ^[2]; Yang, Weitao ^[2]; Hoertz, Paul G. ^[1]; Meyer, Thomas J ^[1]

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1. Univ. of North Carolina, Chapel Hill, NC (United States)
2. Duke Univ., Durham, NC (United States)

As the terminal step in photosystem II, and a potential half-reaction for artificial photosynthesis, water oxidation (2H₂O → O₂ + 4e^- + 4H⁺) is key, but it imposes a significant mechanistic challenge with requirements for both 4e^-/4H^- loss and O—O bond formation. Significant progress in water oxidation catalysis has been achieved recently by use of single-site Ru metal complex catalysts such as [Ru(Mebimpy)(bpy)(OH₂)]²⁺ [Mebimpy = 2,6-bis(1-methylbenzimidazol-2-yl)pyridine; bpy = 2,2'-bipyridine]. When oxidized from Ru^II-OH₂²⁺ to Ru^V = O³⁺, these complexes undergo O—O bond formation by O-atom attack on a H₂O molecule, which is often the rate-limiting step. Microscopic details of O—O bond formation have been explored by quantum mechanical/molecular mechanical (QM/MM) simulations the results of which provide detailed insight into mechanism and a strategy for enhancing catalytic rates. It utilizes added bases as proton acceptors and concerted atom–proton transfer (APT) with O-atom transfer to the O atom of a water molecule in concert with proton transfer to the base (B). Base catalyzed APT reactivity in water oxidation is observed both in solution and on the surfaces of oxide electrodes derivatized by attached phosphonated metal complex catalysts. These results have important implications for catalytic, electrocatalytic, and photoelectrocatalytic water oxidation.

• Research Organization: Energy Frontier Research Centers (EFRC) (United States). Center for Solar Fuels (UNC EFRC)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES)
• DOE Contract Number: SC0001011
• OSTI ID: 1064658
• Journal Information: Proc. Natl. Acad. Sci. USA, Vol. 107, Issue 16; Related Information: UNC partners with University of North Carolina (lead); Duke University; University of Florida; Georgia Institute of Technology; University; North Carolina Central University; Research Triangle Institute
• Publisher: National Academy of Sciences
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
catalysis (homogeneous)
catalysis (heterogeneous)
solar (photovoltaic)
solar (fuels)
photosynthesis (natural and artificial)
hydrogen and fuel cells
electrodes - solar
charge transport
materials and chemistry by design
synthesis (novel materials)
synthesis (self-assembly)