JCAP researchers determined CO2RR reaction mechanisms from Quantum Mechanics free energy Calculations with Explicit water
Quantum Mechanics calculations with a realistic description of water were used to determine the mechanisms from free energy barriers of CO2RR providing an opportunity to use such calculations for designing new selective and active CO2RR catalysts.
Cheng, T., Xiao, H. & Goddard, W. A. Reaction Mechanisms for the Electrochemical Reduction of CO2 to CO and Formate on the Cu(100) Surface at 298 K from Quantum Mechanics Free Energy Calculations with Explicit Water. Journal of the American Chemical Society, DOI: 10.1021/jacs.6b08534 (2016).
Copper (Cu) is currently one of the few well-studied metals that reduces CO2 to hydrocarbons and alcohols and is being extensively used as a “prototype” material to validate and determine the CO2 reduction mechanisms. Copper also serves as a basis for the design of new selective catalysts that can operate under low overpotentials. The product distribution in the CO2RR is known to be a function of the applied potential, while the thermodynamics and kinetics of these reactions are greatly influenced by the processes that occur at the liquid electrolyte and solid electrode interface.
JCAP researchers are actively engaged in both experimental (i.e., recent publication by Favaro, M. et al., DOI: 10.1038/ncomms12695) and theoretical studies geared towards understanding the liquid/solid interfaces in electrochemical reactions. The recent effort led by W. A. Goddard (Cheng, T., Xiao, H. & Goddard, W. A. DOI: 10.1021/jacs.6b08534) focuses on the use of Quantum Mechanics (QM)-based reaction molecular dynamics calculations that include five layers of fully flexible QM water that they applied to the study of electrocatalytic reduction of CO2 to CO and formate on Cu(100) surface at 298Kand pH=7.
To describe the water/Cu(100) interface, the authors included 48 water molecules (1.21 nm thick coverage) on a 4x4 Cu(100) surface slab with an active area of 1.02 nm2. Researchers investigated the reaction mechanisms of CO and formate formations and determined that the lowest kinetic reaction pathway for CO and formate formations are very district and involve different reaction mechanisms.
The conclusion from this study suggests that it should be possible to control product selectivity by modifying either the binding energy of CO2 or formation energy for H* through controlling the pH, alloying, altering properties of the electrolyte solution, or even designing new nanoscale catalysts.
This work is performed by the Joint Center for Artificial Photosynthesis, a DOE Energy Innovation Hub, supported through the Office of Science of the U.S. Department of Energy (Award No. DE-SC0004993). Calculations were carried out on Zwicky astrophysics computing system at Caltech under NSF award CBET 1512759 and National Energy Research Scientific Computing Center, a DOE Office of Science User Facility supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.