期刊
ACS CATALYSIS
卷 7, 期 11, 页码 7680-7687出版社
AMER CHEMICAL SOC
DOI: 10.1021/acscatal.7b03086
关键词
N-doped carbon; oxygen reduction; electrocatalysis; mechanistic studies; density functional theory
资金
- U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences [DE-SC0014176]
- MIT Energy Initiative
- Dreyfus Postdoctoral Fellowship
- U.S. Department of Energy (DOE) [DE-SC0014176] Funding Source: U.S. Department of Energy (DOE)
Using a combination of experimental and computational investigations, we assemble a consistent mechanistic model for the oxygen reduction reaction (ORR) at molecularly well-defined graphite-conjugated catalyst (GCC) active sites featuring aryl-pyridinium moieties (N+-GCC). ORR catalysis at glassy carbon surfaces modified with N+-GCC fragments displays near-first-order dependence in O-2 partial pressure and near-zero-order dependence on electrolyte pH. Tafel analysis suggests an equilibrium one-electron transfer process followed by a rate-limiting chemical step at modest overpotentials that transitions to a rate-limiting electron transfer sequence at higher overpotentials. Finite-cluster computational modeling of the N+-GCC active site reveals preferential O-2 adsorption at electrophilic carbons alpha to the pyridinium moiety. Together, the experimental and computational data indicate that ORR proceeds via a proton-decoupled O-2 activation sequence involving either concerted or stepwise electron transfer and adsorption of O-2, which is then followed by a series of electron/proton transfer steps to generate water and turn over the catalytic cycle. The proposed mechanistic model serves as a roadmap for the bottom-up synthesis of highly active N-doped carbon ORR catalysts.
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