First-principles Simulation of Electrochemical Systems at Fixed Applied Voltage: Vibrational Stark Effect for CO on Platinum Electrodes

Chemisorbed molecules at a fuel-cell electrode are a very sensitive probe of the surrounding electrochemical environment, and one that can be accurately monitored with different spectroscopic techniques. We calculate from first principles the dependence of vibrational frequencies as a function of the electrode voltage (the vibrational Stark effect) for chemisorbed CO molecules, finding excellent agreement with electrochemical spectroscopic experiments and resolving previous controversies. In the process, we develop a comprehensive electrochemical model to study quantum-mechanical systems as a function of the applied voltage.