Operando transient ATR-FTIR for probing plasmonic photoelectrocatalysis mechanisms*

Selectively producing desired products is a key challenge in the CO₂ reduction reaction. Recent experimental observations have shown greatly enhanced selectivity of CO:H2 as well as increased yield of hydrocarbons, when exciting plasmons at the catalyst-electrolyte interface. The mechanisms are so far unclear. We describe an experimental apparatus to tease out the plasmon’s role.

ATR-FTIR has been used to deduce that the dark reaction pathway of CO₂+H₂O→CO depends on applied potential. Our apparatus allows for simultaneous plasmon excitation and FTIR analysis of reaction intermediates. Thus, we can determine how the plasmon affects adsorbed reaction intermediates and pathway. Further, we use the Kretschmann-Raether method to control the plasmon resonance energy, gaining an additional knob to help deduce the plasmonic mechanism.

Finally, we show that the method can be applied to studying strong coupling control of chemical reactions at liquid photoelectrochemical interfaces.