Electrode design for surface enhanced infrared spectroscopy

A flow cell working electrode comprising a first layered structure, the first layered structure comprising:

• a substrate;
• a conductive electrode layer contacting the substrate;
• an electrically resistive layer contacting the conductive electrode layer such that the conductive electrode layer is positioned between the substrate and the electrically resistive layer, the electrically resistive layer having an electrically resistive thickness tailored to reduce electrical conductivity across the electrically resistive layer but to allow an electric field associated with a voltage applied to the conductive electrode layer to be felt across the electrically resistive layer;
• a macroscopically non-conductive plasmonic metal layer contacting the electrically resistive layer such that the electrically resistive layer is positioned between the conductive electrode layer and the macroscopically non-conductive plasmonic metal layer.

A method of using a flow cell working electrode comprising sequentially a substrate, a conductive electrode layer, an electrically resistive layer, and a macroscopically non-conductive plasmonic metal layer, the method comprising:

• a) applying a first voltage to the conductive electrode layer;
• b) during the applying of step a), acquiring an infrared spectrum of molecules of interest present at a surface of the macroscopically non-conductive plasmonic metal layer, the molecules of interest experiencing a first electric field associated with the first voltage;
• c) applying a second voltage to the conductive electrode layer, wherein the second voltage is different than the first voltage;
• d) during the applying of step c), acquiring an infrared spectrum of the molecules of interest, the molecules of interest experiencing a second electric field associated with the second voltage;
• e) generate a report including field-dependent infrared spectra, wherein the field-dependent infrared spectra have a sufficiently low background signal to resolve an OH stretching mode, a CO stretching mode, a CN stretching mode, or a CH stretching mode.