Operando Electrochemical Spectroscopy for CO on Cu(100) at pH 1 to 13: Validation of Grand Canonical Potential Predictions

Electrochemical
reduction of CO2 to value-added products
is an attractive strategy to address issues of increasing atmospheric
CO2 concentration. Cu is the only pure metal catalyst known
to electrochemically convert CO2 to appreciable amounts
of oxygenates and hydrocarbons such as C2H5OH,
CH4, and C2H4, but the Faraday efficiencies
are too low and the onset potentials are too high. To discover electrocatalytic
systems better than Cu, we use in silico strategies
based on new grand canonical potential (GCP) methods, but the complexity
of the electrode–electrolyte interface makes it difficult to
validate the accuracy of GCP. Operando electrochemical
polarization-modulation infrared spectroscopy (PMIRS) provides a performance
benchmark for theoretical tools that account for the vibrational stretching
frequencies of surface-bound CO, νCO, as a function
of pH and applied potential U. We show here that GCP calculations
of the surface coverages of H*, OH*, and CO* on Cu(100) as a function
of U lead to excellent predictions of the potential-dependent νCO and its shift with pH from 1 to 13. This validation justifies
the use of GCP for predicting the performance of catalyst designs.