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Mechanistic Elucidations of Highly Dispersed Metalloporphyrin Metal-Organic Framework Catalysts for CO2 Electroreduction |
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| Authors: | Michael R Smith Clare B Martin Sonia Arumuganainar Ari Gilman Bruce E Koel Michele L Sarazen |
| Institution: | 1. Department of Chemistry, Princeton University, Princeton, NJ 08544 USA
These authors contributed equally to this work.;2. Department of Chemical and Biological Engineering, Princeton University, Princeton, NJ 08544 USA These authors contributed equally to this work.;3. Department of Chemical and Biological Engineering, Princeton University, Princeton, NJ 08544 USA |
| Abstract: | Immobilization of porphyrin complexes into crystalline metal–organic frameworks (MOFs) enables high exposure of porphyrin active sites for CO2 electroreduction. Herein, well-dispersed iron-porphyrin-based MOF (PCN-222(Fe)) on carbon-based electrodes revealed optimal turnover frequencies for CO2 electroreduction to CO at 1 wt.% catalyst loading, beyond which the intrinsic catalyst activity declined due to CO2 mass transport limitations. In situ Raman suggested that PCN-222(Fe) maintained its structure under electrochemical bias, permitting mechanistic investigations. These revealed a stepwise electron transfer-proton transfer mechanism for CO2 electroreduction on PCN-222(Fe) electrodes, which followed a shift from a rate-limiting electron transfer to CO2 mass transfer as the potential increased from −0.6 V to −1.0 V vs. RHE. Our results demonstrate how intrinsic catalytic investigations and in situ spectroscopy are needed to elucidate CO2 electroreduction mechanisms on PCN-222(Fe) MOFs. |
| Keywords: | Electrocatalysis Immobilization Metal–Organic Framework Reaction Mechanism Spectroscopy |