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Title: Comment on 'New Insights in the Electrocatalytic Proton Reduction and Hydrogen Oxidation by Bioinspired Catalysts: A DFT Investigation'

In the title paper, Vetere et al. reported a computational investigation of the mechanism of oxidation of H2 / proton reduction using a model nickel complex for nickel-based electrocatalysts with cyclic phosphorous ligands incorporating pendant amines. These catalysts are attracting considerable attention owing to their high turn-over rates and relatively low overpotentials. These authors interpreted the results of their calculations as evidence for a symmetric bond breaking (forming) of H2 directly to (from) two protonated amines in concert with a 2-electron reduction of the Ni(II) site to form a Ni(0) di-proton state. We show here that this interpretation is erroneous as we report the structure of an heterolytic cleavage transition state consistent with the presence of the Ni(II) center acting as a Lewis acid and of the pendant amines acting as Lewis bases. We determined the associated intrinsic reaction coordinate (IRC) pathway connecting the di-hydrogen (η2-H2) adduct and a hydride-proton state. We also characterize differently the nature of the transition state reported by these authors. H2 oxidation / proton reduction with this class of catalysts is a heterolytic process.
Authors:
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Publication Date:
OSTI Identifier:
1015257
Report Number(s):
PNNL-SA-76591
39981; KC0307010; TRN: US201111%%517
DOE Contract Number:
AC05-76RL01830
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Physical Chemistry A, 115(18):4861-4865; Journal Volume: 115; Journal Issue: 18
Research Org:
Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
08 HYDROGEN; ADDUCTS; AMINES; CATALYSTS; CLEAVAGE; ELECTROCATALYSTS; HYDROGEN; LEWIS ACIDS; LEWIS BASES; NICKEL; OXIDATION; PROTONS catalysis, nickel complexes; Environmental Molecular Sciences Laboratory