Bromine-sensitized solar photolysis of CO2

Mark S Braiman, Wilfried Sailer-Kronlachner, Christopher J. Varjas

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

Direct photochemical reduction of CO2 has generally been accomplished by using transition-metal compounds as electron transfer reagents. Here, we show that elemental bromine can function as an alternative photosensitizer. When sunlight is tightly focused on mixtures of CO2 and Br2, in the presence of a polar adsorbent such as silica gel, glass wool, alumina, or titania, a metastable red adduct is formed within seconds and concentrates at the point of illumination. Further illumination causes deposition of a stable black film on the polar adsorbent. Mass spectrometry of the cold-trapped red intermediate shows clusters of peaks corresponding to the expected distribution of isotopomers of C2O 4Br4 +, as well as of C2O 4Br3 +. DFT computations indicate that the lowest-energy species with the formula C2O4Br4 is trans-2,4-dibromo-2,4-dihypobromo-1,3-dioxetane. Formation of this molecule from (2CO2 + 2Br2) would require a minimum of 3 visible photons, two of which would hypothetically be used in formation of as-yet undetected CO2Br2 and the third, in a subsequent photodimerization. By elemental analysis, the final amorphous solid product contains a C/Br atomic ratio >12, suggesting that Br2 is acting photocatalytically. Even with a poorly optimized optical system, the reaction rate has reached as high as 1.6 mg reduced C with 40 s of solar collection using a 30 cm diameter paraboloid reflector. This rate is consistent with the storage of approximately 1% of incident solar energy.

Original languageEnglish (US)
Pages (from-to)10430-10436
Number of pages7
JournalJournal of Physical Chemistry B
Volume116
Issue number35
DOIs
StatePublished - Sep 6 2012

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Bromine
Photolysis
bromine
adsorbents
Adsorbents
photolysis
Lighting
illumination
Transition metal compounds
wool
Photosensitizing Agents
Photosensitizers
metal compounds
Aluminum Oxide
Silica Gel
Silica gel
solar energy
silica gel
sunlight
Wool

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Materials Chemistry
  • Surfaces, Coatings and Films

Cite this

Bromine-sensitized solar photolysis of CO2 . / Braiman, Mark S; Sailer-Kronlachner, Wilfried; Varjas, Christopher J.

In: Journal of Physical Chemistry B, Vol. 116, No. 35, 06.09.2012, p. 10430-10436.

Research output: Contribution to journalArticle

Braiman, MS, Sailer-Kronlachner, W & Varjas, CJ 2012, 'Bromine-sensitized solar photolysis of CO2 ', Journal of Physical Chemistry B, vol. 116, no. 35, pp. 10430-10436. https://doi.org/10.1021/jp208985y
Braiman, Mark S ; Sailer-Kronlachner, Wilfried ; Varjas, Christopher J. / Bromine-sensitized solar photolysis of CO2 . In: Journal of Physical Chemistry B. 2012 ; Vol. 116, No. 35. pp. 10430-10436.
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