Electrochemical Flow Reactor Design Allows Tunable Mass Transport Conditions for Operando Surface Enhanced Infrared Absorption Spectroscopy

In situ attenuated total reflection surface enhanced infrared absorption spectroscopy (ATR-SEIRAS) is often used to investigate the near-surface electrocatalytic reaction environment. However, there is a gap in directly correlating the near-surface reaction environment with electrocatalytic reaction rates. To that end, we designed an electrochemical flow reactor for operando electrochemical ATR-SEIRAS and demonstrate its capability with the CO2 reduction reaction (CO2RR). Roughened gold catalyst thin films are prepared on ATR silicon crystals as a model system to probe local species under CO2RR conditions in 0.1 M KHCO3. We measured changes in the interfacial CO2 concentration as a function of applied potential and electrolyte flow rate in operando, allowing us to correlate the changes in reaction rates with the observed CO2 concentration. Including the choice of the catalyst and electrolyte, coupling hydrodynamic control with ATR-SEIRAS in this platform enables investigations of how the local microenvironment affects the activity and selectivity of electrochemical reactions.