Momentum Relaxed, Plasmon-Resonant Vibrational Sum Frequency Generation of Electrochemical Interfaces: Direct Observation of Carbon Dioxide Electroreduction on Gold

We present a vibrational sum frequency generation method to probe the Au/electrolyte interface with a detection limit of <1% of a monolayer, and with currents exceeding 1 mA/cm 2 during CO 2 reduction. We couple light to the interface using momentum relaxed surface plasmon resonance. Using this technique we make in-situ measurements of catalytic CO with good signal-to-noise and at high current density.