Attenuated total reflection, surface enhanced infrared absorption spectroscopy (ATR-SEIRAS) is a spectrochemical method that can detect changes in concentrations of electroactive species near an electrode surface as well as adsorbed intermediates. However, its application to heterogeneous redox reactions is still infrequent due to complex working electrode fabrication procedures. This study presents a simple procedure for fabricating ATR-SEIRAS platinum electrodes and demonstrates the effectiveness of the procedure with a successful examination of the Fe(CN)6^3-(aq) / Fe(CN)6^4-(aq) reaction. We found that electrode resistance measurements supported by atomic force microscopy were accurate indicators of ATR-SEIRAS response and ATR electrode thickness. Working electrodes with resistances of 600 Ω were approximately 2.4 ± 0.3 nm in thickness and enabled clear detection of the ferrocyanide peak at 2040 cm^-1 with universal wafers. Decreasing electrode thickness to 1.0 ± 0.3 nm improved signal strength by 50 %. Polarization tests revealed the formation of adsorbed intermediates at 2070 cm^-1 with both positive and negative polarizations consistent with an inner sphere reaction mechanism. Applying large positive polarizations (>900 mV vs. SHE) formed additional cyanoplatinate complexes, indicating electrode degradation at large applied potentials.

Increasing interest in spectroelectrochemisty due to its versatility and far-reaching applications has led to its rapid growth in recent years. Attenuated total reflectance (ATR), Fourier transform infrared spectroscopy (FTIR) is one technique that can provide valuable insights into surface interactions provided a viable working electrode can be fabricated. Though ATR working electrodes can be deposited using a range of techniques such as argon sputtering, vapor deposition and electrodeposition, published studies typically do not report electrode thicknesses which are a key in obtaining repeatable signal responses. Here we examine different approaches to quantify ATR electrode thicknesses and screen for optimal electrode configurations. The test system used to assess different approaches for validating electrode performance was the ferri-ferrocyanide redox reaction with an argon sputtered platinum surface. It was found that atomic force microscopy, ellipsometry and optical profilometry had practical limitations operating in the nanometer range and were not adequate for predicting spectroscopic outcomes. In contrast, electrochemical impedance spectroscopy (EIS) measurements accurately predicted high performing ATR working electrodes. For an 11 mm by 9 mm ATR wafer, favorable signal strengths corresponded to cell impedances greater than 500 Ω. Cell constant calculations determined that platinum thickness layers needed to be less than 4 nm to provide consistent spectroelectrochemical responses.