Molecular-Level Insights into Oxygen Reduction Catalysis by Graphite-Conjugated Active Sites
| Autor: | Matthew Welborn, Yogesh Surendranath, Troy Van Voorhis, Tomohiro Fukushima, Alexander T. Murray, Nathan D. Ricke, James J. Shepherd |
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| Rok vydání: | 2017 |
| Předmět: |
Tafel equation
biology Chemistry Inorganic chemistry Active site 02 engineering and technology General Chemistry Glassy carbon 010402 general chemistry 021001 nanoscience & nanotechnology Electrocatalyst Photochemistry 01 natural sciences Catalysis 0104 chemical sciences chemistry.chemical_compound Electron transfer biology.protein Moiety QD Pyridinium 0210 nano-technology |
| Zdroj: | ACS Catalysis. 7:7680-7687 |
| ISSN: | 2155-5435 |
| Popis: | 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. |
| Databáze: | OpenAIRE |
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