Proton-coupled electron transfer at modified electrodes by multiple pathways

Journal Article · Mon Dec 12 00:00:00 EST 2011 · Proceedings of the National Academy of Sciences of the United States of America

DOI:https://doi.org/10.1073/pnas.1115769108· OSTI ID:1065956

Chen, Z. ^[1]; Vannucci, A. K. ^[1]; Concepcion, J. J. ^[1]; Jurss, J. W. ^[1]; Meyer, T. J. ^[1]

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1. Univ. of North Carolina, Chapel Hill, NC (United States). Dept. of Chemistry

In single site water or hydrocarbon oxidation catalysis with polypyridyl Ru complexes such as [Ru^II(Mebimpy)(bpy)(H₂O)]²⁺ [where bpy is 2,2'-bipyridine, and Mebimpy is 2,6-bis(1-methylbenzimidazol-2-yl)pyridine] 2, or its surface-bound analog [Ru^II(Mebimpy)(4,4'-bis-methlylenephosphonato-2,2'-bipyridine)(OH₂)]²⁺ 2-PO₃H₂, accessing the reactive states, Ru^V = O³⁺/Ru^IV = O²⁺, at the electrode interface is typically rate limiting. The higher oxidation states are accessible by proton-coupled electron transfer oxidation of aqua precursors, but access at inert electrodes is kinetically inhibited. The inhibition arises from stepwise mechanisms which impose high energy barriers for 1e- intermediates. Oxidation of the Ru^III-OH²⁺ or Ru^III-OH₂³⁺ forms of 2-PO₃H₂ to Ru^IV = O²⁺ on planar fluoride-doped SnO₂ electrode and in nanostructured films of Sn(IV)-doped In₂O₃ and TiO₂ has been investigated with a focus on identifying microscopic phenomena. The results provide direct evidence for important roles for the nature of the electrode, temperature, surface coverage, added buffer base, pH, solvent, and solvent H₂O/D₂O isotope effects. In the nonaqueous solvent, propylene carbonate, there is evidence for a role for surface-bound phosphonate groups as proton acceptors.

• 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: 1065956
• Journal Information: Proceedings of the National Academy of Sciences of the United States of America, Vol. 108, Issue 52; 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; ISSN 0027-8424
• Publisher: National Academy of Sciences, Washington, DC (United States)
• 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)