Surface and Structural Investigation of a MnOx Birnessite-Type Water Oxidation Catalyst Formed under Photocatalytic Conditions

Benjamin J. Deibert, Jingming Zhang, Paul F. Smith, Karena W. Chapman, Sylvie Rangan, Debasis Banerjee, Kui Tan, Hao Wang, Nicholas Pasquale, Feng Chen, Ki Bum Lee, G. Charles Dismukes, Yves J. Chabal, Jing Li

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16 Citations (Scopus)

Abstract

Catalytically active MnOx species have been reported to form in situ from various Mn-complexes during electrocatalytic and solution-based water oxidation when employing cerium(IV) ammonium ammonium nitrate (CAN) oxidant as a sacrificial reagent. The full structural characterization of these oxides may be complicated by the presence of support material and lack of a pure bulk phase. For the first time, we show that highly active MnOx catalysts form without supports in situ under photocatalytic conditions. Our most active 4MnOx catalyst (∼0.84 mmol O2 mol Mn-1 s-1) forms from a Mn4O4 bearing a metal-organic framework. 4MnOx is characterized by pair distribution function analysis (PDF), Raman spectroscopy, and HR-TEM as a disordered, layered Mn-oxide with high surface area (216 m2g-1) and small regions of crystallinity and layer flexibility. In contrast, the SMnOx formed from Mn2+ salt gives an amorphous species of lower surface area (80 m2g-1) and lower activity (∼0.15 mmol O2 mol Mn-1 s-1). We compare these catalysts to crystalline hexagonal birnessite, which activates under the same conditions. Full deconvolution of the XPS Mn2p3/2 core levels detects enriched Mn3+ and Mn2+ content on the surfaces, which indicates possible disproportionation/comproportionation surface equilibria.

Original languageEnglish
Pages (from-to)14218-14228
Number of pages11
JournalChemistry - A European Journal
Volume21
Issue number40
DOIs
Publication statusPublished - Sep 1 2015

Keywords

  • birnessite structure
  • manganese oxide
  • metal-organic frameworks
  • water oxidation catalyst
  • water splitting

ASJC Scopus subject areas

  • Catalysis
  • Organic Chemistry

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    Deibert, B. J., Zhang, J., Smith, P. F., Chapman, K. W., Rangan, S., Banerjee, D., Tan, K., Wang, H., Pasquale, N., Chen, F., Lee, K. B., Dismukes, G. C., Chabal, Y. J., & Li, J. (2015). Surface and Structural Investigation of a MnOx Birnessite-Type Water Oxidation Catalyst Formed under Photocatalytic Conditions. Chemistry - A European Journal, 21(40), 14218-14228. https://doi.org/10.1002/chem.201501930