TY - JOUR
T1 - 2-Pyridinide as an Active Catalytic Intermediate for CO 2 Reduction on p-GaP Photoelectrodes
T2 - Lifetime and Selectivity
AU - Xu, Shenzhen
AU - Carter, Emily A.
N1 - Publisher Copyright:
Copyright © 2018 American Chemical Society.
PY - 2018/7/18
Y1 - 2018/7/18
N2 - The active intermediate responsible for pyridine (Py)-catalyzed reduction of CO 2 on a p-GaP photoelectrode is currently under debate. Exploration of the proposed intermediates' available pathways for further reaction may yield a deeper understanding of the CO 2 reduction mechanism that will be essential to designing better cocatalysts in such photoelectrochemical systems. Adsorbed 2-pyridinide (2-PyH - ∗) was recently proposed by Carter and co-workers to be an intermediate that facilitates hydride transfer (HT) to CO 2 to produce formate. However, the lifetime of 2-PyH - ∗, most likely controlled by the rate of 2-PyH - ∗ protonation to form adsorbed dihydropyridine (DHP∗), is still in question. In this work, we provide evidence for the transient existence of 2-PyH - ∗ on a p-GaP surface by comparing the activation energy for HT to CO 2 to those predicted for 2-PyH - ∗ being protonated to form either DHP∗ or Py∗ + H 2 via a hydrogen evolution reaction (HER). We predict that 2-PyH - ∗ situated next to an adjacent surface hydroxide (OH - ∗) will be the most effective intermediate leading to CO 2 reduction on p-GaP. Predicted high barriers of HER (via either 2-PyH - ∗ or H - ∗) also explain the high selectivity toward CO 2 reduction observed in experiments.
AB - The active intermediate responsible for pyridine (Py)-catalyzed reduction of CO 2 on a p-GaP photoelectrode is currently under debate. Exploration of the proposed intermediates' available pathways for further reaction may yield a deeper understanding of the CO 2 reduction mechanism that will be essential to designing better cocatalysts in such photoelectrochemical systems. Adsorbed 2-pyridinide (2-PyH - ∗) was recently proposed by Carter and co-workers to be an intermediate that facilitates hydride transfer (HT) to CO 2 to produce formate. However, the lifetime of 2-PyH - ∗, most likely controlled by the rate of 2-PyH - ∗ protonation to form adsorbed dihydropyridine (DHP∗), is still in question. In this work, we provide evidence for the transient existence of 2-PyH - ∗ on a p-GaP surface by comparing the activation energy for HT to CO 2 to those predicted for 2-PyH - ∗ being protonated to form either DHP∗ or Py∗ + H 2 via a hydrogen evolution reaction (HER). We predict that 2-PyH - ∗ situated next to an adjacent surface hydroxide (OH - ∗) will be the most effective intermediate leading to CO 2 reduction on p-GaP. Predicted high barriers of HER (via either 2-PyH - ∗ or H - ∗) also explain the high selectivity toward CO 2 reduction observed in experiments.
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U2 - 10.1021/jacs.8b03774
DO - 10.1021/jacs.8b03774
M3 - Article
C2 - 29901999
AN - SCOPUS:85048662829
SN - 0002-7863
VL - 140
SP - 8732
EP - 8738
JO - Journal of the American Chemical Society
JF - Journal of the American Chemical Society
IS - 28
ER -