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

21 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

Fingerprint

Photocatalysis
Porphyrins
porphyrins
Oxides
metal oxides
Metals
Electrons
Oxidation
Charge injection
oxidation
Water
kinetics
Conduction bands
Absorption spectroscopy
random walk
Kinetic parameters
leaves
water
Charge transfer
absorption spectroscopy

ASJC Scopus subject areas

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

Cite this

Towards multielectron photocatalysis : A porphyrin array for lateral hole transfer and capture on a metal oxide surface. / Brennan, Bradley J.; Durrell, Alec C.; Koepf, Matthieu; Crabtree, Robert H.; Brudvig, Gary W.

In: Physical Chemistry Chemical Physics, Vol. 17, No. 19, 21.05.2015, p. 12728-12734.

Research output: Contribution to journalArticle

Brennan, Bradley J. ; Durrell, Alec C. ; Koepf, Matthieu ; Crabtree, Robert H. ; Brudvig, Gary W. / Towards multielectron photocatalysis : A porphyrin array for lateral hole transfer and capture on a metal oxide surface. In: Physical Chemistry Chemical Physics. 2015 ; Vol. 17, No. 19. pp. 12728-12734.
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