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Pyrazine reservoirs that lower cobalt HER overpotential
Moving a redox-active pyrazine on a cobalt polypyridine ligand cuts hydrogen-evolution overpotential by about 200 mV versus pyridine analogues in water.
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What ligand swap stores extra electrons on cobalt HER catalysts?
Pyrazine in place of pyridine as a pendant redox reservoir.
Source: Bioinspired design of redox-active ligands for multielectron catalysis: effects of positioning pyrazine reservoirs on cobalt for electro- and photocatalytic generation of hydrogen from water · DOI · quote verified
How much easier to reduce is pyrazine vs pyridine?
Gas-phase electron affinity ca. 0.6 eV more positive.
Source: Bioinspired design of redox-active ligands for multielectron catalysis: effects of positioning pyrazine reservoirs on cobalt for electro- and photocatalytic generation of hydrogen from water · DOI · quote verified
How much overpotential is gained vs pyridine analogues?
About 200 mV.
Source: Bioinspired design of redox-active ligands for multielectron catalysis: effects of positioning pyrazine reservoirs on cobalt for electro- and photocatalytic generation of hydrogen from water · DOI · quote verified
Does the pyrazine position matter?
Yes: isomers display markedly different reactivities.
Source: Bioinspired design of redox-active ligands for multielectron catalysis: effects of positioning pyrazine reservoirs on cobalt for electro- and photocatalytic generation of hydrogen from water · DOI · quote verified
In what medium is H2 evolved?
Photocatalytic hydrogen from water at neutral pH.
Source: Bioinspired design of redox-active ligands for multielectron catalysis: effects of positioning pyrazine reservoirs on cobalt for electro- and photocatalytic generation of hydrogen from water · DOI · quote verified
Why make Zn(II) analogues?
Redox-inactive Zn disentangles metal-centered vs ligand-centered redox.
Source: Bioinspired design of redox-active ligands for multielectron catalysis: effects of positioning pyrazine reservoirs on cobalt for electro- and photocatalytic generation of hydrogen from water · DOI · quote verified
How is electrocatalytic H2 quantified?
Micro-GC of headspace versus charge assuming 100% Faradaic efficiency.
Source: Bioinspired design of redox-active ligands for multielectron catalysis: effects of positioning pyrazine reservoirs on cobalt for electro- and photocatalytic generation of hydrogen from water · DOI · quote verified
What working electrode is used in phosphate buffer CPE?
Hg pool, 19.6 cm2, in a two-compartment H-cell.
Source: Bioinspired design of redox-active ligands for multielectron catalysis: effects of positioning pyrazine reservoirs on cobalt for electro- and photocatalytic generation of hydrogen from water · DOI · quote verified
What broader design lesson do the authors draw?
Placement of redox non-innocent ligands matters for multielectron transformations.
Source: Bioinspired design of redox-active ligands for multielectron catalysis: effects of positioning pyrazine reservoirs on cobalt for electro- and photocatalytic generation of hydrogen from water · DOI · quote verified
Prior related Co catalysts operated in what water?
pH 7 buffered water and seawater.
Source: Bioinspired design of redox-active ligands for multielectron catalysis: effects of positioning pyrazine reservoirs on cobalt for electro- and photocatalytic generation of hydrogen from water · DOI · quote verified
What computational method supports the electronic picture?
Density functional calculations on the cobalt complexes.
Source: Bioinspired design of redox-active ligands for multielectron catalysis: effects of positioning pyrazine reservoirs on cobalt for electro- and photocatalytic generation of hydrogen from water · DOI · quote verified