Oxidation mechanism of formic acid on the bismuth adatom-modified Pt(111) surface

In order to improve catalytic processes, elucidation of reaction mechanisms is essential. Here, supported by a combination of experimental and computational results, the oxidation mechanism of formic acid on Pt(111) electrodes modified by the incorporation of bismuth adatoms is revealed. In the proposed model, formic acid is first physisorbed on bismuth and then deprotonated and chemisorbed in formate form, also on bismuth, from which configuration the C-H bond is cleaved, on a neighbor Pt site, yielding CO2. It was found computationally that the activation energy for the C-H bond cleavage step is negligible, which was also verified experimentally.This work has been financially supported by the MINECO (Spain) (project CTQ2013-44083-P) and Generalitat Valenciana (project PROMETEOII/2014/013).Perales Rondón, JV.; Ferre Vilaplana, A.; Feliu, J.; Herrero, E. (2014). Oxidation mechanism of formic acid on the bismuth adatom-modified Pt(111) surface. Journal of the American Chemical Society. 136(38):13110-13113. https://doi.org/10.1021/ja505943hS13110131131363

Determination of Specific Electrocatalytic Sites in the Oxidation of Small Molecules on Crystalline Metal Surfaces

The identification of active sites in electrocatalytic reactions is part of the elucidation of mechanisms of catalyzed reactions on solid surfaces. However, this is not an easy task, even for apparently simple reactions, as we sometimes think the oxidation of adsorbed CO is. For surfaces consisting of non-equivalent sites, the recognition of specific active sites must consider the influence that facets, as is the steps/defect on the surface of the catalyst, cause in its neighbors; one has to consider the electrochemical environment under which the “active sites” lie on the surface, meaning that defects/steps on the surface do not partake in chemistry by themselves. In this paper, we outline the recent efforts in understanding the close relationships between site-specific and the overall rate and/or selectivity of electrocatalytic reactions. We analyze hydrogen adsorption/desorption, and electro-oxidation of CO, methanol, and ammonia. The classical topic of asymmetric electrocatalysis on kinked surfaces is also addressed for glucose electro-oxidation. The article takes into account selected existing data combined with our original works.M.J.S.F. is grateful to PNPD/CAPES (Brazil). J.M.F. thanks the MCINN (FEDER, Spain) project-CTQ-2016-76221-P

Balance of the interfacial interactions of 4,4′-bipyridine at Bi(111) surface

The data from impedance spectroscopy, electrochemical in situ scanning tunnelling microscopy (STM), surface-enhanced infrared adsorption spectroscopy (SEIRAS) and density functional theory (DFT) were measured, combined and analysed to describe the 4,4′-bipyridine (4,4′-BP) adsorption at Bi(111) single crystal electrode from weakly acidified 0.5 M and 0.05 M Na 2SO4 aqueous solutions (pH ≈ 5.5÷6.0). The influence of electrode potential (E) on the adsorption kinetics of 4,4′-bipyridine on Bi(111) has been demonstrated. The capacitance pits in the differential capacitance versus E curve have been observed. The in situ STM data reveal two molecular patterns at different concentration of the supporting electrolyte. The stable adsorbate adlayer detectable by using the infrared spectroscopy method has been observed within E from -0.75 to -0.5 V (vs. Ag|AgCl sat. KCl). The results of DFT calculations and SEIRAS data have been used to establish the various possible orientations of the 4,4′-BP molecules at Bi(111) surface. The DFT investigation has been focused on the factors governing the self-assembly of 4,4′-BP, such as the intermolecular van der Walls attractions and interplay between the surface and the nanostructure lattices, both essential for the interfacial self-assembly