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Boosting CO-to-CO evolution using a bimetallic diketopyrrolopyrrole tethered rhenium bipyridine catalyst
The use of homogeneous electro- and photo-catalysis involving molecular catalysts offers valuable insight into reaction mechanisms as it relates to the structure-function of these tunable systems. However, supported molecular catalysts ( i.e. , hybrid electrodes) are multiplexed and not fully unders...
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| Published in: | Catalysis science & technology 2022-10, Vol.12 (21), p.6427-6436 |
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| Main Authors: | , , , , |
| Format: | Article |
| Language: | |
| Online Access: | Get full text |
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| Summary: | The use of homogeneous electro- and photo-catalysis involving molecular catalysts offers valuable insight into reaction mechanisms as it relates to the structure-function of these tunable systems. However, supported molecular catalysts (
i.e.
, hybrid electrodes) are multiplexed and not fully understood with regards to specific support-catalyst interactions. Even so, it still remains that catalyst activity for CO
2
electroreduction can be tuned by modifying specific functional groups to achieve performance enhancement. Herein, a series of derivatized [Re(bpy)(CO)
3
Cl] catalysts were prepared with molecular structures having variability in both the number of Re-centers and π-conjugated diketopyrrolopyrrole (DPP) units. While tethering [Re(bpy)(CO)
3
Cl] to the DPP unit had a negligible effect on molecular electro- and photo-catalyst properties in organic solvent, the DPP chromophore enabled facile coupling of two [Re(bpy)(CO)
3
Cl] moieties. As a homogeneous species, the bimetallic system effectively doubles the rate of CO
2
-to-CO conversion in the reaction-diffusion layer achieving a TOF
CO
= 1000 s
−1
and FEco% = 98% for up to 6 hours of electrolysis as the two catalytic centers act independently. Immobilization onto carbon hybrid electrodes was found to evolve H
2
, where the ratio of CO :H
2
produced during electrolysis depended on both the molecular structure of the catalyst and the additive(s) to the carbon surface used to suppress the hydrogen evolution reaction (HER). Introducing a commercial DPP-based polymer and/or colloid imprinted carbons (CICs) into carbon paper favours CO evolution from the catalyst by suppressing the HER at carbon and by dispersing the molecular catalyst across a larger more wettable surface to mitigate mass transport limitations. Once again, the bimetallic catalyst has the highest activity in comparison to the monometallic analogues, with a selectivity (FEco% = 53%), activity (TOF = 39 h
−1
), and longevity (active for up to 5 hours) for CO
2
-to-CO evolution from aqueous electrolyte.
The use of homogeneous electro- and photo-catalysis involving molecular catalysts offers valuable insight into reaction mechanisms as it relates to the structure-function of these tunable systems. |
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| ISSN: | 2044-4753 2044-4761 |
| DOI: | 10.1039/d2cy01453j |