Electrooxidation of ethanol on Pt and PtRu surfaces investigated by ATR surface-enhanced infrared absorption spectroscopy

Abstract

Neste trabalho, investigou-se pela primeira vez a eletrooxidação de etanol em eletrodepósitos de Pt e PtRu em meio ácido através da técnica de absorção e reflexão de infravermelho em superfície com reflexão total atenuada (ATR-SEIRAS) in situ. O desenho experimental elimina as fracas absorbâncias associadas a espécies adsorvidas, usualmente observadas para superfícies eletrodepositadas (rugosas), e permite que se acompanhe o recobrimento superficial por CO em função do potencial, para ambos os catalisadores. A dinâmica da adsorção-oxidação de CO foi acompanhada por ATR-SEIRAS (para quatro concentrações de etanol) e correlacionada com expressões derivadas de um modelo cinético simples. A análise cinética sugere que o desenvolvimento da camada de CO não é influenciado pela presença de Ru ou pela concentração de etanol. Os resultados apontam que a quebra da ligação CC independe do recobrimento com Ru e provavelmente acontece em sítios de Pt. Herein, it was investigated for the first time the electro-oxidation of ethanol on Pt and PtRu electrodeposits in acidic media by using in situ surface enhanced infrared absorption spectroscopy with attenuated total reflection (ATR-SEIRAS). The experimental setup circumvents the weak absorbance signals related to adsorbed species, usually observed for rough, electrodeposited surfaces, and allows a full description of the CO coverage with the potential for both catalysts. The dynamics of adsorption-oxidation of CO was accessed by ATR-SEIRAS experiments (involving four ethanol concentrations) and correlated with expressions derived from a simple kinetic model. Kinetic analysis suggests that the growing of the CO adsorbed layer is nor influenced by the presence of Ru neither by the concentration of ethanol. The results suggest that the CC scission is not related to the presence of Ru and probably happens at Pt sites.

Activity and Stability of Pt/IrO2 Bifunctional Materials as Catalysts for the Oxygen Evolution/Reduction Reactions

“…When the platinum loading was increased beyond 70%, the peak at 0.69 V becomes the major peak, and for platinum black the peak at 0.79 V becomes just a shoulder. Multiple peaks in platinum CO stripping experiments have been associated with the degree of CO coverage on the electrode and the adsorption of CO on different Pt sites, such as terraces, edges and corners. − A single CO oxidation peak at ∼0.7 V for pure Pt was also obtained in other works. , …”

“…46−48 A single CO oxidation peak at ∼0.7 V for pure Pt was also obtained in other works. 49,50 The catalysts' A ecsa calculated through the integration of CO stripping curves (Figure 5b) are presented in Table 2. A decrease in the A ecsa values can be observed in line with the Pt content enhancement in the studied electrocatalysts (Pt/IrO 2 1:9 > Pt/IrO 2 3:7 > Pt/IrO 2 1:1 > Pt black), varying from 28.6 m Pt 2 g Pt −1 for the Pt/IrO 2 1:9 material to 8.3 m Pt 2 g Pt −1 for the Pt black catalyst.…”

Electrocatalytic Efficiency of the Oxidation of Small Organic Molecules under Oscillatory Regime

“…We have recently found that the electro-oxidation of 1 mol L –1 ethanol containing acid solution over platinum, at oscillatory regime, results in a rather small production of carbon dioxide, if compared with the production of acetaldehyde. Moreover, we showed some evidence that acetic acid is also produced as a partially oxidized species, and it is likely that adsorbates such as CH x,ads , CO ads , OH ads , and CH 3 CHO ads , ,,− might take part in the oscillatory cycle. Despite scarce mechanistic studies on the oscillatory electro-oxidation of ethanol, it is possible to establish a trend in the poisoning rate by comparison with studies on ethanol and C1 molecules.…”

Dissolution Stability: The Major Challenge in the Regenerative Fuel Cells Bifunctional Catalysis

“…The Pt/IrO x stripping profile exhibits a single peak centered at ∼0.69 V with a shoulder at ∼0.73 V, such profile is similar to that of Pt black material, and had also been reported for others Pt catalysts. 52,53 Regarding the Pt/IrO 2 catalyst, the CO stripping profile exhibits two peaks: a main peak at ∼0.67 V and a higher potential peak at ∼0.75 V. The Pt electroactive surface areas (A ECSA ) were calculated by integration of stripping peaks of Fig. 2b, and the values are shown in Table I.…”