Frustrated Lewis pairs oxidize H2 without metals
A carbon Lewis acid, BArF18, and lutidine cleave H2 and oxidize it at carbon electrodes about 1 V milder, without CO poisoning.
Source
Metal-free electrocatalytic hydrogen oxidation using frustrated Lewis pairs and carbon-based Lewis acids
What they did
Authors combined a carbon-based Lewis acid (1+), a boron hydride-shuttle (BArF18), and 2,6-lutidine, tracked H2 activation by NMR and CV, and cycled bulk electrolysis at carbon paper.
What they found
Pre-formed 1-H lowers the H2 oxidation potential by ~1 V (~197 kJ mol−1) and another 110 mV versus prior FLP electrochemistry. After 25 min at 20 °C, 30% of 1+ is hydrided; conversion is quantitative in 17 h. The system tolerates CO and avoids H2-evolution side reactions.
The limits
What it doesn't show
An operating H2/O2 fuel cell and a fully air-stable boron FLP are future goals; a fourth H2 charge failed until more lutidine was added.
Key terms
- Frustrated Lewis pair (FLP)
- Sterically prevented LA/LB pair that can heterolytically split H2.
- Hydride shuttle
- [(μ-H)(BArF18)2]− that moves hydride from the boron FLP to 1+.
- 1+ / 1-H
- Carbon Lewis acid and its hydride, the electrocatalytic couple.
- CO tolerance
- No binding or inhibition when the mixture is sparged with CO.
- BArF18
- Fluorinated aryl borane used with lutidine to activate H2.
Flashcards
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Quiz yourself
The H2 oxidation potential drops by about:
Common questions
How much does the potential drop?
About 1 V at carbon electrodes (~197 kJ mol−1).
Is it metal-free?
Yes—catalytic in the carbon Lewis acid 1+.
Does CO poison it?
No—unlike Pt or many hydrogenase mimics.
How fast is hydriding?
30% in 25 min at 20 °C; full in 17 h.
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