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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Understanding nascent plasmons and metallic bonding in atomically precise gold nanoclusters
The metallic bond is arguably the most intriguing one among the three types of chemical bonds, and the resultant plasmon excitation ( e.g. in gold nanoparticles) has garnered wide interest. Recent progress in nanochemistry has led to success in obtaining atomically precise nanoclusters (NCs) of hundreds of atoms per core. In this work, thiolate-protected Au 279 (SR) 84 and Au 333 (SR) 79 NCs, both in the nascent metallic state are investigated by cryogenic optical spectroscopy down to 2.5 K. At room temperature, both NCs exhibit distinct plasmon resonances, albeit the NCs possess a gap (estimated 0.02–0.03 eV, comparable to thermal energy). Interestingly, we observe no effect on plasmons with the transition from the metallic state at r.t. to the insulating state at cryogenic temperatures (down to 2.5 K), indicating a nonthermal origin for electron-gas formation. The electronic screening-induced birth of metallic state/bonding is discussed. The obtained insights offer deeper understanding of the nascent metallic state and covalent-to-metallic bonding evolution, as well as plasmon birth from concerted excitonic transitions.
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- Award ID(s):
- 1808675
- NSF-PAR ID:
- 10342175
- Date Published:
- Journal Name:
- Chemical Science
- Volume:
- 13
- Issue:
- 7
- ISSN:
- 2041-6520
- Page Range / eLocation ID:
- 1925 to 1932
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/d1sc06819a
