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Title: Elucidating the active sites for CO 2 electroreduction on ligand-protected Au 25 nanoclusters
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 more » 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. « less
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Catalysis Science & Technology
Page Range or eLocation-ID:
3795 to 3805
Sponsoring Org:
National Science Foundation
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