TY - JOUR
T1 - Single Molecule Electrochemistry
T2 - Impact of Surface Site Heterogeneity
AU - Fu, Bo
AU - Van Dyck, Colin
AU - Zaleski, Stephanie
AU - Van Duyne, Richard P.
AU - Ratner, Mark A.
N1 - Funding Information:
This work was supported by Air Force Office of Scientific Research MURI (FA9550-14-1-0003). We gratefully acknowledge the computational resources from the Quest high performance computing facility at Northwestern University and the Extreme Science and Engineering Discovery Environment (XSEDE) Program, which is supported by National Science Foundation Grant ACI-1053575. S.Z. acknowledges Michael Mattei for helpful discussions.
PY - 2016/12/8
Y1 - 2016/12/8
N2 - Probing the electrochemistry of single molecules is a direct pathway toward a microscopic understanding of a variety of electron transfer processes related to energy science, such as electrocatalysis and solar fuel cells. In this context, Zaleski et al. recently studied the single electron transfer reaction of the dye molecule rhodamine-6G (R6G) by electrochemical single molecule surface-enhanced Raman spectroscopy (EC-SMSERS) (J. Phys. Chem. C 2015, 119, 28226-28234). In that work, the reductions of the dye molecule R6G were not only observed in the same potential range as in the ensemble surface cyclic voltammogram but also seen under some less negative potentials. Aiming to understand and explain this experiment theoretically, we relate the binding energy of R6G+ adsorbed on a silver nanoparticle (AgNP) to its reduction potential and further use periodic density functional theory to calculate this adsorption energy at different local surface sites. Well-defined crystal facets and defective surfaces, are considered. We find that the calculated adsorption energy distribution of the strongest binding states at each surface site closely matches the potential range of the experimentally observed Faradaic events. Moreover, the underpotential events are explained by the metastable adsorption states with less binding strength compared with those corresponding to Faradaic events. Our study reveals the importance of the heterogeneity of surface structures on the AgNP and offers a new perspective on understanding single molecule electrochemical behavior. (Graph Presented).
AB - Probing the electrochemistry of single molecules is a direct pathway toward a microscopic understanding of a variety of electron transfer processes related to energy science, such as electrocatalysis and solar fuel cells. In this context, Zaleski et al. recently studied the single electron transfer reaction of the dye molecule rhodamine-6G (R6G) by electrochemical single molecule surface-enhanced Raman spectroscopy (EC-SMSERS) (J. Phys. Chem. C 2015, 119, 28226-28234). In that work, the reductions of the dye molecule R6G were not only observed in the same potential range as in the ensemble surface cyclic voltammogram but also seen under some less negative potentials. Aiming to understand and explain this experiment theoretically, we relate the binding energy of R6G+ adsorbed on a silver nanoparticle (AgNP) to its reduction potential and further use periodic density functional theory to calculate this adsorption energy at different local surface sites. Well-defined crystal facets and defective surfaces, are considered. We find that the calculated adsorption energy distribution of the strongest binding states at each surface site closely matches the potential range of the experimentally observed Faradaic events. Moreover, the underpotential events are explained by the metastable adsorption states with less binding strength compared with those corresponding to Faradaic events. Our study reveals the importance of the heterogeneity of surface structures on the AgNP and offers a new perspective on understanding single molecule electrochemical behavior. (Graph Presented).
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U2 - 10.1021/acs.jpcc.6b05252
DO - 10.1021/acs.jpcc.6b05252
M3 - Article
AN - SCOPUS:85006021714
VL - 120
SP - 27241
EP - 27249
JO - Journal of Physical Chemistry C
JF - Journal of Physical Chemistry C
SN - 1932-7447
IS - 48
ER -