Towards multielectron photocatalysis: A porphyrin array for lateral hole transfer and capture on a metal oxide surface

Bradley J. Brennan, Alec C. Durrell, Matthieu Koepf, Robert H. Crabtree, Gary W. Brudvig

Research output: Contribution to journalArticle

23 Citations (Scopus)

Abstract

Current molecular water-oxidation photoelectrocatalytic cells have substantial kinetic limitations under normal solar photon flux where electron-hole recombination processes may outcompete charge buildup on the catalytic centers. One method of overcoming these limitations is to design a system where multiple light-harvesting dyes work cooperatively with a single catalyst. We report a porphyrin monomer/dyad array for analysis of lateral hole transfer on a SnO2 surface consisting of a free-base porphyrin that functions to absorb light and initiate charge injection into the conduction band of SnO2, which leaves a positive charge on the organic moiety, and a free-base porphyrin/Zn-porphyrin dyad molecule that functions as a thermodynamic trap for the photoinduced holes. By using transient absorption spectroscopy, we have determined that the holes on the surface-bound free-base porphyrins are highly mobile via electron self-exchange between close-packed neighbors. The lateral charge-transfer processes were modelled by treating the system statistically with a random-walk method that utilizes experimentally derived kinetic parameters. The results of the modelling indicate that each self-exchange (hop) occurs within 25 ns and that the holes are efficiently transferred to the Zn-porphyrin. This hole-harvesting scheme provides a framework for enhancing the efficiency of multielectron photoelectrocatalytic reactions such as the four-electron oxidation of water.

Original languageEnglish
Pages (from-to)12728-12734
Number of pages7
JournalPhysical Chemistry Chemical Physics
Volume17
Issue number19
DOIs
Publication statusPublished - May 21 2015

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ASJC Scopus subject areas

  • Physics and Astronomy(all)
  • Physical and Theoretical Chemistry

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