Fourier Transform Infrared Spectroscopy Study of CO Electro-oxidation on Pt(111) in Alkaline Media

Abstract

In this work we investigate the electro-oxidation of CO on Pt(111) in alkaline solution by using Fourier transform infrared spectroscopy (FTIRS), to determine the adsorption sites of the CO, the intermediate species and the final oxidation product as a function of the applied potential. Multiple CO vibration bands (on-top, bridge and 3-fold hollow site) are observed on the Pt(111) electrode, their distribution and potential dependence being strongly dependent on the surface treatment. Spectroscopic results show that the final reaction product is carbonate and suggest that adsorbed carbonate blocks the access of CO from the (111) terrace to the active sites (i.e., step and kink sites).

Effect of the Surface Structure of Pt(100) and Pt(110) on the Oxidation of Carbon Monoxide in Alkaline Solution: an FTIR and Electrochemical Study

“…Additionally, a red shift of the CO L and CO B band centers is observed, compared to the experiment carried out with the Pt(100) surface annealed in CO/Ar. Again, this band center shift may be attributed to the higher amount of defects on these surfaces [18]. These latter observations emphasise the importance of long-range order to obtain a compressed CO adlayer and confirm the previous observation obtained by analysis of the charges, that is, on the CO/Ar annealed surfaces, the CO coverage is larger due to the large order surface structure and the absence of islands.…”

“…fast cooling down in air), the voltametric profile of the Fig. 7b presents a "pre-wave" (0.3-0.5 V) that was found previously for the Pt(111) surface, and it could be ascribed to oxidation of CO at defect sites, more specifically kink sites [8,18]. Increasing the electrode potential from 0.5 to 0.7 V, two overlapping contributions in the CO oxidation can be observed, and those might be associated to the oxidation of CO on terrace sites.…”

“…Moreover, from the same figure is observable that CO adsorbed in bridge configuration is the most strongly adsorbed CO (i.e. the least reactive) and is completely removed from the Pt surface at potentials higher than 0.65 V. The latter was observed during the CO oxidation on slightly disordered Pt(111) electrode in alkaline media [18], in which it was associated to CO adsorbed in a bridge site on the top of the step site. Therefore, this CO b is oxidised by OH adsorbed on the Pt (100) terrace at very positive potentials.…”

“…in an H 2 /Ar atmosphere, is required for Pt(100) and stepped Pt surfaces [13][14][15][16][17] to obtain a well-ordered surface. It was also found by our group that different annealing procedures of the Pt(111) produce different surfaces with different CO vibrational signatures and CO oxidation behavior [18]. The effect of the annealing/cooling preparation on the surface structure of the Pt(110) surface has also been studied.…”

“…As in our previous study on the electro-oxidation of CO on Pt(111) [18], our experiments involved a combination of cyclic voltammetry and in situ Fourier transform infrared (FTIR) spectroscopy. The influence of different surface preparations of the Pt(100) and Pt(110) surface on the CO adsorption and oxidation will also be examined.…”