(269f) Grand Canonical DFT Investigation of CO2 Electroreduction on Noble and Transition Metal Surfaces

Recent advances in the implementation of grand canonical electronic density functional theory enable constant potential calculations for states along the reaction coordinate of electrochemical processes (R. Sundararaman et al. J. Chem. Phys. 146, 114107 (2017)). The algorithm consists of variationally optimizing the number of electrons to converge the grand free energy at fixed potential with the net electronic charge neutralized using continuum solvation method. We tested this technique to investigate CO₂ electroreduction to CO on Ag(111), Au(111), Cu(111), Ir(111), Ni(111), Pd(111), Pt(111) and Rh(111) surfaces and compared the results from those obtained via the widely used computational hydrogen electrode method (J. Norskov, J. Phys. Chem. B 108, 17886 (2004)). The free energy profiles predicted from both schemes yielded similar thermodynamic limiting steps with associated overpotential that are not significantly different from each other. On coinage metals, for example, the first reduction step is the thermodynamic limiting step. Calculations of the kinetic barriers and their potential dependencies are currently underway.