(509w) Self-Assembled Monolayers for Electrocatalysis: A Theoretical Study of CO2 Reduction Reaction to CO over Ag | AIChE

(509w) Self-Assembled Monolayers for Electrocatalysis: A Theoretical Study of CO2 Reduction Reaction to CO over Ag


Yang, Z. - Presenter, University of Massachusetts-Lowell
Che, F., University of Massachusetts Lowell
Gu, Z., University of Massachusetts Lowell
Self-assembled monolayers (SAMs) have been used in many applications, including sensing, nanofabrication, and catalysis. 4-Mercaptobenzonitrile (4-MBN) attracts increasing interests to understand key electrochemical characteristics via the Stark effect. The delocalized electrons in 4-MBN can show stabilization effects via non-local interaction and modified electronic properties over metal surfaces, where the heterogeneous catalysis occurs. Despite the potential catalytic ability of 4-MBN SAMs, few works explore catalytic properties of 4-MBN SAMs. The catalytical electroreduction of CO2 (CO2RR) into valuable products provides a sustainable/carbon-neutral approach to store the renewable energy. Ag exhibits good CO2-to-CO selectivity compared to other metallic catalysts. However, the major limitations of CO2-to-CO over Ag are: (1)high overpotential of the initial CO2 activation; (2) low stability of surface under-coordinated active site under high-overpotential condition. One approach is the surface modification by catalytic SAMs.

First-principles density functional theory (DFT) calculations were performed on 4-MBN/Ag systems. DFT calculations show that the presence of 4-MBN SAMs stabilized the Ag(211) facet, a high-catalytic active facet during CO2RR-to-CO reaction (Figure 1(a)). A local high electric field near Ag induced by 4-MBN SAMs was observed and found linearly proportional to 4-MBN coverages (Figure 1(b)). The induced local electric field was able to alter electronic properties of Ag surfaces and, thus, might change thermodynamics and kinetics of the initial CO2 activation under electrocatalytic conditions (i.e., external electric fields at the electrode/electrolyte interface). We then applied an external electric field to the CO product adsorption. With 4-MBN SAMs, dipole moment and polarizability of the CO adsorption over Ag surfaces were notably influenced as shown in Figure 1(c). Additionally, we observed that 4-MBN SAMs exhibited new organic active sites to activate CO2 and stabilize OCOH*. The surface stabilization effect and electronic surface modification via 4-MBN SAMs provide a new strategy for catalyst design with high efficiency and activity.