The electro-oxidation of formate ions at a polycrystalline Pt electrode in alkaline solution: an in situ FTIR study

Abstract

This paper reports in situ FTIR studies on the oxidation of formate at polycrystalline Pt in aqueous KOH. Data are presented which show that hydroxyl species play a major role in the electro-oxidation of small organic molecules under alkaline conditions at polycrystalline Pt, and that a number of possible mechanistic pathways are possible. Small changes in experimental conditions appear to be able to cause the reaction to flick between these pathways; for example, the presence of oxygen has a marked effect upon the observed electrochemistry. In contrast to acid solution, our postulated model includes the formation of intermediates bonded through O atoms, rather than C, as being an important option in alkaline solution. Finally, the pH distribution across the reflective electrode in external reflectance IR is modelled and significant variations in pH across the electrode surface in FTIR cells predicted and confirmed experimentally.

Computational screening for selective catalysts: Cleaving the C C bond during ethanol electro-oxidation reaction

“…14 In line with other experimental studies, [15][16][17]10,11,7,18,19 we found that a 5 potential improvement in the selectivity lies in the competition between two routes represented schematically in Figure 1.…”

“…9 Christensen et al have shown that the interfacial pH drops at higher potentials due to the high consumption of OH -which is not completely counterbalanced by the OH -diffusion from the bulk-phase. [10][11][12] This phenomenon leads to a transition from alkaline to acidic conditions at the interphase. The transition potential varies with the diffusion rate of OH -which is dependent on the temperature and mass flow-rate.…”

An in situ FTIR spectroscopic study of the electrochemical oxidation of ethanol at a Pb-modified polycrystalline Pt electrode immersed in aqueous KOH

“…This poor selectivity for ethanol oxidation to carbonate at Pt has been attributed to [8] the adsorption of the ethanol molecule via the O atom on the C 1 carbon; the removal of the first two electrons from the adsorbate then generates acetaldehyde, CH 3 CHO, which is able to desorb (see scheme 1) as such, but can also itself be oxidised in a second two-electron step to acetate, which in turn can be displaced from the surface by the ethanol in solution. Work in Newcastle on methanol [9], formate [10] and ethanol [11] oxidation supports this postulate in terms of oxidation in alkaline media, with clear evidence of adsorption through O rather than through C, and with evidence that it is adsorption through the the latter of which is necessary for C-C cleavage.…”

“…3(a) show: the growth of water gain features near 3335 cm À1 and 1647 cm À1 , the loss of OH À (broad bands near 2700 and 1875 cm À1 ref. [9][10][11], the gain of a band due to bridgebonded CO (CO B ) at 1862 cm À1 , 19,20 the gain of a band near 1395 cm À1 with a small gain feature at ca. 1300 cm À1 .…”

An in Situ FTIR Study of Ethanol Oxidation at Polycrystalline Platinum in 0.1 M KOH at 25 and 50 °C

“…[43]; this value varies very little between 14 ºC and 45 ºC[44]. The substantial drop in pH in thin-layer FTIR spectroscopic experiments has been modelled in terms of the slow diffusion of OHions across the electrode surface coupled with the exhaustion of reactant[31][32].…”