Computational study of anomalous reduction potentials for hydrogen evolution catalyzed by cobalt dithiolene complexes

Brian H. Solis, Sharon Hammes-Schiffer

Research output: Contribution to journalArticle

Abstract

The design of efficient hydrogen-evolving catalysts based on earth-abundant materials is important for developing alternative renewable energy sources. A series of four hydrogen-evolving cobalt dithiolene complexes in acetonitrile-water solvent is studied with computational methods. Co(mnt) 2 (mnt = maleonitrile-2,3-dithiolate) has been shown experimentally to be the least active electrocatalyst (i.e., to produce H 2 at the most negative potential) in this series, even though it has the most strongly electron-withdrawing substituents and the least negative Co III/II reduction potential. The calculations provide an explanation for this anomalous behavior in terms of protonation of the sulfur atoms on the dithiolene ligands after the initial Co III/II reduction. One fewer sulfur atom is protonated in the Co II(mnt) 2 complex than in the other three complexes in the series. As a result, the subsequent Co II/I reduction step occurs at the most negative potential for Co(mnt) 2. According to the proposed mechanism, the resulting Co I complex undergoes intramolecular proton transfer to form a catalytically active Co III-hydride that can further react to produce H 2. Understanding the impact of ligand protonation on electrocatalytic activity is important for designing more effective electrocatalysts for solar devices.

Original languageEnglish (US)
Pages (from-to)15253-15256
Number of pages4
JournalJournal of the American Chemical Society
Volume134
Issue number37
DOIs
StatePublished - Sep 19 2012

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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