Using density functional theory (DFT) calculations, we investigated the electrochemical reduction of CO 2 and the competing H 2 evolution reaction on ligand-protected Au 25 nanoclusters (NCs) of different charge states, Au 25 (SR) 18 q ( q = −1, 0, +1). Our results showed that regardless of charge state, CO 2 electroreduction over Au 25 (SR) 18 q NCs was not feasible because of the extreme endothermicity to stabilize the carboxyl (COOH) intermediate. When we accounted for the removal of a ligand (both –SR and –R) from Au 25 (SR) 18 q under electrochemical conditions, surprisingly we found that this is a thermodynamically feasible process at the experimentally applied potentials with the generated surface sites becoming active centers for electrocatalysis. In every case, the negatively charged NCs, losing a ligand from their surface during electrochemical conditions, were found to significantly stabilize the COOH intermediate, resulting in dramatically enhanced CO 2 reduction. The generated sites for CO 2 reduction were also found to be active for H 2 evolution, which agrees with experimental observations that these two processes compete. Interestingly, we found that the removal of an –R ligand from the negatively charged NC, resulted in a catalyst that was both active and selective for CO 2 reduction. This work highlights the importance of both the overall charge state and generation of catalytically active surface sites on ligand-protected NCs, while elucidating the CO 2 electroreduction mechanisms. Overall, our work rationalizes a series of experimental observations and demonstrates pathways to convert a very stable and catalytically inactive NC to an active electrocatalyst.
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Bifunctional electrocatalysis for CO 2 reduction via surface capping-dependent metal–oxide interactions
Multi-component materials are a new trend in catalyst development for electrochemical CO 2 reduction. Understanding and managing the chemical interactions within a complex catalyst structure may unlock new or improved reactivity, but is scientifically challenging. We report the first example of capping ligand-dependent metal–oxide interactions in Au/SnO 2 structures for electrocatalytic CO 2 reduction. Cetyltrimethylammonium bromide capping on the Au nanoparticles enables bifunctional CO 2 reduction where CO is produced at more positive potentials and HCOO − at more negative potentials. With citrate capping or no capping, the Au–SnO 2 interactions steer the selectivity toward H 2 evolution at all potentials. Using electrochemical CO oxidation as a probe reaction, we further confirm that the metal–oxide interactions are strongly influenced by the capping ligand.
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- Award ID(s):
- 1651717
- NSF-PAR ID:
- 10157173
- Date Published:
- Journal Name:
- Chemical Communications
- Volume:
- 55
- Issue:
- 60
- ISSN:
- 1359-7345
- Page Range / eLocation ID:
- 8864 to 8867
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/C9CC02934F
