Electron-transfer sensitization of H2 oxidation and CO 2 reduction catalysts using a single chromophore

Nathan Todd La Porte, Davis B. Moravec, Michael D. Hopkins*

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review

    8 Scopus citations

    Abstract

    Energy-storing artificial-photosynthetic systems for CO2 reduction must derive the reducing equivalents from a renewable source rather than from sacrificial donors. To this end, a homogeneous, integrated chromophore/two-catalyst system is described that is thermodynamically capable of photochemically driving the energy-storing reverse water-gas shift reaction (CO2 + H2 → CO + H2O), where the reducing equivalents are provided by renewable H2. The system consists of the chromophore zinc tetraphenylporphyrin (ZnTPP), H2 oxidation catalysts of the form [CpRCr(CO)3]-, and CO2 reduction catalysts of the type Re(bpy-4,4′-R2)(CO) 3Cl. Using time-resolved spectroscopic methods, a comprehensive mechanistic and kinetic picture of the photoinitiated reactions of mixtures of these compounds has been developed. It has been found that absorption of a single photon by broadly absorbing ZnTPP sensitizes intercatalyst electron transfer to produce the substrate-active forms of each. The initial photochemical step is the heretofore unobserved reductive quenching of the low-energy T1 state of ZnTPP. Under the experimental conditions, the catalytically competent state decays with a second-order half-life of ∼15 μs, which is of the right magnitude for substrate trapping of sensitized catalyst intermediates.

    Original languageEnglish (US)
    Pages (from-to)9745-9750
    Number of pages6
    JournalProceedings of the National Academy of Sciences of the United States of America
    Volume111
    Issue number27
    DOIs
    StatePublished - Jul 8 2014

    Keywords

    • Artificial photosynthesis
    • Catalysis
    • Dual catalysis
    • Photocatalysis
    • Photoredox

    ASJC Scopus subject areas

    • General

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