Investigating the presence of adsorbed species on Pt steps at low potentials

Abstract

The study of the OH adsorption process on Pt single crystals is of paramount importance since this adsorbed species is considered the main intermediate in many electrochemical reactions of interest, in particular, those oxidation reactions that require a source of oxygen. So far, it is frequently assumed that the OH adsorption on Pt only takes place at potentials higher than 0.55 V (versus the reversible hydrogen electrode), regardless of the Pt surface structure. However, by CO displacement experiments, alternating current voltammetry, and Raman spectroscopy, we demonstrate here that OH is adsorbed at more negative potentials on the low coordinated Pt atoms, the Pt steps. This finding opens a new door in the mechanistic study of many relevant electrochemical reactions, leading to a better understanding that, ultimately, can be essential to reach the final goal of obtaining improved catalysts for electrochemical applications of technological interest.

On the oxidation of isopropanol on platinum single crystal electrodes. A detailed voltammetric and FTIR study

“…This shift follows the behavior of OH adsorption on the terraces which also shifts to higher values as the step density increases [34]. On the other hand, adsorbed OH on the steps, which occurs at potentials positive to the characteristic peak for the step sites (0.13 V and 0.32 V for the (110) and (100) steps, respectively) [35] seems to be unreactive for the oxidation of isopropanol because no oxidation current is observed after the peaks. In fact, the signals for the H/OH adsorption on the peaks are still observed in the presence of isopropanol, which indicates that no species derived from isopropanol are adsorbed on the step sites.…”

The Role of Bismuth in Suppressing the CO Poisoning in Alkaline Methanol Electrooxidation: Switching the Reaction from the CO to Formate Pathway

“…Two different regions clearly stand out: hydrogen adsorption/desorption (H ads/des ) at potentials lower than 0.45 V and the OH adsorption/desorption (OH ads/des ) region, that occurs at potentials higher than 0.55 V. 30 In the H ads/des region, the adsorption of hydrogen is substantially suppressed in the case of Pt 92 Bi 8 , probably arising from the abundant surface OH ad even in the potential range of H ads/des . 30,31 In the OH ads region, Pt 92 Bi 8 shows three intense oxidation peaks. Their assignments hold the key to revealing the roles of Bi, which will be discussed in detail in the following section.…”

“…Figure 3c shows the adsorption states of Pt NPs and Pt 92 Bi 8 recorded in 1 M KOH at a scan rate of 50 mV s −1 . Two different regions clearly stand out: hydrogen adsorption/desorption (H ads/des ) at potentials lower than 0.45 V and the OH adsorption/desorption (OH ads/des ) region, that occurs at potentials higher than 0.55 V. 30 In the H ads/des region, the adsorption of hydrogen is substantially suppressed in the case of Pt 92 Bi 8 , probably arising from the abundant surface OH ad even in the potential range of H ads/des . 30,31 In the OH ads region, Pt 92 Bi 8 shows three intense oxidation peaks.…”

Boosting ethanol electrooxidation at RhBi alloy and Bi2O3 composite surfaces in alkaline media

“…This redox pair could be due to the adsorption (or formation) and desorption (or reduction) of surface O ad /OH ad species. 67 Interestingly, it also shows two characteristic peaks near 0.24 and 0.3 V at the RhBi–Bi 2 O 3 surface. They can be attributed to OH ad absorption on the freestanding surface of Bi 2 O 3 since the measurement on carbon-supported Bi 2 O 3 /C shows the same voltammetric curve in Fig.…”