CO oxidation on stepped-Pt(111) under electrochemical conditions: insights from theory and experiment

The co-adsorption of CO and OH on two Pt stepped surfaces vicinal to the (111) orientation has been evaluated by means of density functional theory (DFT) calculations. Focusing on Pt(533) and Pt(221), which contain (100) and (111)-steps, respectively, we find that (111)-steps should be more reactive towards CO oxidation than surfaces containing (100)-steps. The DFT results are compared with electrochemical experiments on the CO adsorption and oxidation on these vicinal surfaces.This work has been supported by the European Union through the Marie-Curie-ITN ELCAT. Further, J.B., A.C.-V. and T.J. gratefully acknowledge support from the “Deutsche Forschungsgemeinschaft” (DFG) as well as from the bwGRiD for computing resources. Further, support from the European Research Council through the ERC-StG THEOFUN is gratefully acknowledged. E.H. and C. B.-R. also acknowledge the support from MICIN (project no. CTQ2010-16271)

Influence of the CO Adsorption Environment on Its Reactivity with (111) Terrace Sites in Stepped Pt Electrodes under Alkaline Media

The effect of the electrode potential in the reactivity of platinum stepped single crystal electrodes with (111) terraces toward CO oxidation has been studied. It is found that the CO adlayer is significantly affected by the potential at which the adlayer is formed. The electrochemical and FTIR experiments show that the adsorbed CO layer formed in acidic solution at 0.03 V vs SHE is different from that formed at −0.67 V vs SHE in alkaline solutions. The major effect of the electrode potential is a change in the long-range structure of CO adlayer. The adlayer formed in alkaline media presents a higher number of defects. These differences affect the onset and peak potential for CO stripping experiments. The stripping voltammogram for the adlayer formed at −0.67 V vs SHE always shows a prewave and the peak potential is more negative than that observed for the adlayer formed at 0.03 V vs SHE. This means that the apparent higher activity for CO oxidation observed in alkaline media is a consequence of the different CO adlayer structure on the (111) terrace, and not a true catalytic effect. The different behavior is discussed in terms of the different mobility of CO observed depending on the electrode potential. Also, the FTIR frequencies are used to estimate the pzc (potential of zero charge) for the Pt(111) electrode covered with a CO adlayer.M.J.S.F would like to thanks CNPq, Brazil, for financial support for his stay at Universidad de Alicante. This work has been financially supported by the MICINN (Spain) (project CTQ2010-16271) and Generalitat Valenciana (project PROMETEO/2009/045, FEDER)

Adatom modified shape-controlled platinum nanoparticles towards ethanol oxidation

Different adatom modified shape-controlled Pt nanoparticles have been prepared and their electrocatalytic properties have been evaluated toward ethanol electrooxidation. Based on previous findings with Pt model surfaces, Sn, Rh, Ru and Pb adatoms have been selected as promising surface modifiers. The different adatoms have been gradually incorporated on the surface of the preferentially oriented (100) and (111) Pt nanoparticles under electrochemical conditions. The results obtained in 0.5 M H2SO4 indicated that, among the selected adatoms, Sn-modified nanoparticles displayed not only a significant shift to negative values on the onset potential of the ethanol oxidation, but also an important decrease on the hysteresis between the positive and negative sweeps. Interestingly, in chronoamperometic measurements at 0.6 V, the oxidation enhancement factors have been found to be dependent on the surface structure of the Pt nanoparticles. On the other hand, Ru and Pb-modified Pt nanoparticles only presented a rather small oxidation enhancement, whereas the activity of the Rh-modified Pt nanoparticles clearly diminished. In alkaline solutions, the oxidation mechanism changes, and the adsorption of Rh, Sn and Pb on the platinum surfaces just displays small catalytic effect at lower coverage for the potential onset in the voltammetric experiments. Ru adsorption does not present any positive effect over the reaction.This work has been financially supported by the Ministerio de Economía y Competitividad (project CTQ2013-44083-P) and Generalitat Valenciana (project PROMETEOII/2014/013)

Oxidation of ethanol on platinum nanoparticles: surface structure and aggregation effects in alkaline medium

The ethanol oxidation reaction in 0.1 M NaOH on Pt nanoparticles with different shapes and loadings was investigated using electrochemical and spectroscopic techniques. The surface structure effect on this reaction was studied using well-characterized platinum nanoparticles. Regardless of the type of Pt nanoparticles used, results show that acetate is the main product with negligible CO2 formation. From the different samples used, the nanoparticles with a large amount (111) of ordered domains have higher peak currents and a higher onset potential, in agreement with previous works with single crystal electrodes. In addition, spherical platinum nanoparticles supported on carbon with different loadings were used for studying possible diffusional problems of ethanol to the catalyst surface. The activity in these samples diminishes with the increase of Pt loading, due to diffusional problems of ethanol throughout the whole Pt nanoparticle layer, being the internal part of the catalyst layer inactive for the oxidation. To avoid this problem and prepare more dispersed nanoparticle catalyst layers, deposits were dried while the carbon support was rotated to favor the dispersion of the layer around the support. The improvement in the electrocatalytic activity for ethanol oxidation confirms the better performance of this procedure for depositing and drying.This work has been financially supported by the Ministerio de Economía y Competitividad and Generalitat Valenciana through projects CTQ2013-44083-P and PROMETEOII/2014/013, respectively

Glycerol electrooxidation on Pd modified Au surfaces in alkaline media: Effect of the deposition method

The catalytic effect of Pd on gold electrodes for glycerol oxidation is evaluated for Pd-Au surfaces prepared using three different methods: irreversible adsorption of palladium by a simple immersion of a gold electrode in palladium solution, the deposition of palladium on the gold substrate by a step potential from 1 to 0.75 V, and the forced deposition of palladium on the gold electrode with the help of a reducing hydrogen atmosphere. Voltammetry has been used for the electrochemical characterization of the Pd-Au deposits and to determine its reactivity towards glycerol oxidation, whereas FTIR experiments have allowed detecting adsorbed species and products formed during the oxidation reaction. Pd-Au surfaces prepared by irreversible adsorption are the electrodes that show the highest activity for the glycerol complete oxidation to carbonate, whereas Pd-Au surfaces made by the step potential are the catalyst that exhibits the highest rate for the formation and adsorption CO before carbonate production, poisoning the surface and diminishing their electrocatalytic properties. In addition to carbonate, glycerate, glycolate, and formate are detected as oxidation products. The integrated bands of the spectra are used to give quantitative information for comparing the product distribution of the different Pd-Au deposits prepared.This work has been financially supported by the Ministerio de Economía y Competitividad and Generalitat Valenciana by Project Nos. CTQ2016-76221-P and PROMETEOII/2014/013, respectively. G.A.B.M. also thanks her post-doctorate fellowship from CNPq (Grant No. PDE 233268/2014-6)

Nuevos materiales didácticos para descubrir los aspectos más cotidianos de la Electroquímica

A pesar del amplio abanico de aplicaciones que posee la electroquímica, con importantes repercusiones en muchos aspectos de la vida cotidiana, los egresados de química de las universidades españolas poseen en general un notable desconocimiento de esta materia. Con objeto de hacer más atractivo el aprendizaje de esta parte de la química, al tiempo que se revelan algunas de sus aplicaciones menos conocidas, se han preparado nuevos materiales didácticos. En ellos se describen de manera divulgativa algunas de las aplicaciones más importantes de la electroquímica, como son las baterías, síntesis de aluminio, o su uso en biosensores. Los nuevos materiales se han suministrado al alumnado del primer curso del grado de química de la Universidad de Alicante y se ha pedido su opinión a través de una encuesta. En general la recepción ha sido buena, aunque la respuesta de los estudiantes ha sido algo escasa. Para dar mayor difusión, se está creando una página web con estos mismos contenidos. Esta página web se ha puesto a disposición de los alumnos de la asignatura Electroquímica de 4º curso de la licenciatura (plan a extinguir) de Química y de nuevo se pedirá su opinión a través de un formulario web

Ethanol oxidation on shape-controlled platinum nanoparticles at different pHs: A combined in situ IR spectroscopy and online mass spectrometry study

Ethanol oxidation on different shape-controlled platinum nanoparticles at different pHs was studied using electrochemical, Attenuated Total Reflection-Fourier Transform Infrared Spectroscopy (ATR-FTIR) and, especially, Differential Electrochemical Mass Spectrometry (DEMS) techniques, the latter giving interesting quantitative information about the products of ethanol oxidation. Two Pt nanoparticle samples were used for this purpose: (100) and (111) preferentially oriented Pt nanoparticles. The results are in agreement with previous findings that the preferred decomposition product depends on surface structure, with COads formation on (100) domains and acetaldehyde/acetic acid formation on (111) domains. However, new information has been obtained about the changes in CHx and CO formation at lower potentials when the pH is changed, showing that CHx formation is favored against the decrease in CO adsorption on (100) domains. At higher potentials, complete oxidation to CO2 occurs from both CHx and CO fragments. In (111) Pt nanoparticles, the splitting of Csingle bondC bond is hindered, favoring acetaldehyde and acetate formation even in 0.5 M H2SO4. C1 fragments become even less when the pH increases, being nearly negligible in the highest pH studied.This work has been financially supported by the MCINN-FEDER (Spain) and Generalitat Valenciana through projects CTQ 2013-44083-P and PROMETEO/2014/013, respectively

Formic acid electrooxidation on thallium modified platinum single crystal electrodes

Formic acid electrooxidation on Tl modified Pt single crystal electrodes has been carried out in sulfuric acid media. Voltammetric experiments demonstrated that Pt(100) modified by Tl displays a significant enhancement towards formic acid oxidation both lowering the oxidation onset potential and increasing the maximum current density in the positive going-sweep. A similar behavior has been observed in Pt(s)[(100)x(111)] stepped surfaces. On the other hand, for Pt(111) surfaces, the incorporation of Tl also induced a shift of the oxidation onset to lower potential values, a diminution of the hysteresis between the positive and negative going-sweep and also an increase of the oxidation currents. These results have been corroborated using in situ FTIR experiments, where the CO adsorption band disappears completely when Pt(100) and its vicinal surfaces are modified by Tl adatom, leading to the formation of CO2 at lower overvoltages.This work has been financially supported by the MINECO (Spain) (projects CTQ2013-44083-P and CTQ2013-48280-C3-3-R) and Generalitat Valenciana (project PROMETEOII/2014/013, FEDER)

Formic acid electrooxidation on thallium-decorated shape-controlled platinum nanoparticles: an improvement in electrocatalytic activity

Thallium modified shape-controlled Pt nanoparticles were prepared and their electrocatalytic activity towards formic acid electrooxidation was evaluated in 0.5 M sulfuric acid. The electrochemical and in situ FTIR spectroscopic results show a remarkable improvement in the electrocatalytic activity, especially in the low potential region (around 0.1–0.2 V vs. RHE). Cubic Pt nanoparticles modified with Tl were found to be more active than the octahedral Pt ones in the entire range of Tl coverages and potential windows. In situ FTIR spectra indicate that the promotional effect produced by Tl results in the inhibition of the poisoning step leading to COads, thus improving the onset potential for the complete formic acid oxidation to CO2. Chronoamperometric experiments were also performed at 0.2 V to evaluate the stability of the electrocatalysts at constant potential. Finally, experiments with different concentrations of formic acid (0.05–1 M) were also carried out. In all cases, Tl-modified cubic Pt nanoparticles result to be the most active. All these facts reinforce the importance of controlling the surface structure of the electrocatalysts to optimize their electrocatalytic properties.This work has been financially supported by the MICINN (Spain) (project CTQ2010-16271) and Generalitat Valenciana (project PROMETEO/2009/045 – FEDER)

Functionalization of a Few-Layer Antimonene with Oligonucleotides for DNA Sensing

This document is the Accepted Manuscript version of a Published Work that appeared in final form in ACS Applied Nano Materials, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see: https://pubs.acs.org/doi/abs/10.1021/acsanm.0c00335Antimonene, a novel group 15 two-dimensional material, is functionalized with an oligonucleotide as a first step to DNA sensor development. The functionalization process leads to a few-layer antimonene modified with DNA that after deposition on gold screen-printed electrodes gives a simple and efficient DNA electrochemical sensing platform. We provide theoretical and experimental data of the DNA–antimonene interaction, confirming that oligonucleotides interact noncovalently but strongly with antimonene. The potential utility of this antimonene-based sensing device is assessed using, as a case of study, a sequence from the BRCA1 gene as the target DNA. The selectivity of the device allows not only recognition of a specific DNA sequence but also detection of a mutation in this gene associated with breast cancer, directly in clinical samplesThe Ministerio de Ciencia Innovación y Universidades (Grants CTQ2017-84309-C2-1-R, MAT2016-77608-C3-1-P, PCI2018-093081, JTC2017/2D-Sb&Ge, and FIS2016-80434-P), Generalitat Valenciana (Grant APOSTD/2017/010), and CAM (Grants TransNANOAVANSENS and 2017-T1/BIO-5435) are gratefully acknowledged. We also acknowledge the María de Maeztu Programme for Units of Excellence in R&D (MDM-2014-0377), the Fundación Ramón Areces, and the computer resources and assistance provided by the Centro de Computación Científica of the Universidad Autónoma de Madri