Understanding the complementarities of surface-enhanced infrared and Raman spectroscopies in CO adsorption and electrochemical reduction

Abstract

In situ/operando surface enhanced infrared and Raman spectroscopies are widely employed in electrocatalysis research to extract mechanistic information and establish structure-activity relations. However, these two spectroscopic techniques are more frequently employed in isolation than in combination, owing to the assumption that they provide largely overlapping information regarding reaction intermediates. Here we show that surface enhanced infrared and Raman spectroscopies tend to probe different subpopulations of adsorbates on weakly adsorbing surfaces while providing similar information on strongly binding surfaces by conducting both techniques on the same electrode surfaces, i.e., platinum, palladium, gold and oxide-derived copper, in tandem. Complementary density functional theory computations confirm that the infrared and Raman intensities do not necessarily track each other when carbon monoxide is adsorbed on different sites, given the lack of scaling between the derivatives of the dipole moment and the polarizability. Through a comparison of adsorbed carbon monoxide and water adsorption energies, we suggest that differences in the infrared vs. Raman responses amongst metal surfaces could stem from the competitive adsorption of water on weak binding metals. We further determined that only copper sites capable of adsorbing carbon monoxide in an atop configuration visible to the surface enhanced infrared spectroscopy are active in the electrochemical carbon monoxide reduction reaction.

Catalyst Regeneration via Chemical Oxidation Enables Long-Term Electrochemical Carbon Dioxide Reduction

“…The intensity of the bands at around 2075 cm –1 corresponding to the linearly adsorbed CO decreases when the current density increases from 60 mA cm –2 to 90 mA cm –2 , indicating that C–C coupling is promoted. A closer look at the data points to a redshift in the ν­(CO) frequency from 2073 to 2083 cm –1 , giving a Stark tuning factor of about 13 cm –1 /V, close to the 19 cm –1 /V value previously reported . The C–C coupling also results in weaker bands at around 280  and 360 cm –1 for adsorbed CO species at 90 mA cm –2 .…”

“…A closer look at the data points to a redshift in the ν(CO) frequency from 2073 to 2083 cm −1 , giving a Stark tuning factor of about 13 cm −1 /V, close to the 19 cm −1 /V value previously reported. 50 The C−C coupling also results in weaker bands at around 280 � and 360 cm −1 for adsorbed CO species at 90 mA cm −2 . The retention of the band at around 530 cm −1 for Cu−OH is interesting, which can be explained by the increase of local pH near the catalyst surface at high current densities.…”

Tailoring Coordination Microenvironment of Cu(I) in Metal–Organic Frameworks for Enhancing Electroreduction of CO2to CH4

“…The inconsistency between the *CO band observed in in situ Raman at the potential range of −0.6−0.8 V and *CO peaks appeared in the full range of tested potentials in ATR‐SEIRAS may arise from the general lack of scaling between the derivatives of the dipole moments and polarizabilities as reported recently. [ 63 ]…”

“…The inconsistency between the *CO band observed in in situ Raman at the potential range of −0.6−0.8 V and *CO peaks appeared in the full range of tested potentials in ATR-SEIRAS may arise from the general lack of scaling between the derivatives of the dipole moments and polarizabilities as reported recently. [63] DFT calculations were carried out to obtain further insight into the high activity and selectivity of CuI for CO 2 reduction to CH 4 compared with those of CuCl and CuBr. All spin-polarized first-principle computations were performed under the framework of DFT.…”

A Review of One‐Dimensional Nanomaterials as Electrode Materials for Oxygen Reduction Reaction Electrocatalysis

“…These different structures depending on their properties are widely utilized in electrocatalytic enhancement strategies. Many other researchers also are trying to continuously reveal and define these properties through better characterization tools (such as In situ IR/Raman spectroscopy complementary [139] ) and theoretical computational methods [140] . Strengthening the link between the electrocatalytic calculations and experiments facilitates our insight into the mechanism of electrocatalysis.…”