Abstract:
:Optimization of hydride transfer (HT) catalysts to enhance rates and selectivities of (photo)electroreduction reactions could be a crucial component of a sustainable chemical industry. Here, we analyze how ring functionalization of the adsorbed transient intermediate 2-pyridinide (2-PyH-*)-predicted to form in situ from pyridine (Py) in acidified water at a cathode surface and to be the key to selective CO2 photoelectroreduction on p-GaP-may enhance catalytic activity. Earlier studies revealed that 2-PyH-*'s instability results from a protonation side reaction producing adsorbed dihydropyridine (DHP*), which is relatively HT-inactive. Reducing the electron density on 2-PyH-* could limit this protonation, with the trade-off that it may become less active for HT from 2-PyH-*-R to CO2 We explore here how Py functionalization affects the electron distribution and in turn tunes the catalytic performance of 2-PyH-*. We indeed find that electron-withdrawing groups could enhance the stability of 2-PyH-* by reducing its electron density on the ring. Furthermore, we find that the change in the number of electrons on the substituting group of the hydride donor is a good descriptor for both the stability against protonation and the magnitude of the HT barrier. We predict that -CH2-CH2F is the best candidate substituent, as it significantly improves the stability of 2-PyH-* with only a small increase in HT barrier. -CH=CH2 and -CH2F also could be promising, although they require further investigation due to a larger HT-barrier increase.
journal_name
Proc Natl Acad Sci U S Aauthors
Xu S,Carter EAdoi
10.1073/pnas.1911948116subject
Has Abstractpub_date
2019-11-12 00:00:00pages
22953-22958issue
46eissn
0027-8424issn
1091-6490pii
1911948116journal_volume
116pub_type
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