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Publications (707)
The oxidation of formic acid (FAOR) is a critical reaction for direct formic acid fuel cells (DFAFCs), offering high theoretical efficiency and potential for sustainable energy conversion. This study investigates the FAOR mechanism on well-defined Pt-Pd alloy single-crystal surfaces, focusing on the role of Pd incorporation in modifying the electro...
This study explores the electrochemical properties of rhodium polycrystalline electrodes applied to the glycerol oxidation reaction (GOR) in an alkaline medium. Our findings demonstrate that rhodium (Rh) surfaces exhibit catalytic activity by facilitating C−C bond cleavage at low potentials. Employing in situ Fourier-transform infrared (FTIR) spect...
This research explores the glycerol electrooxidation reaction (GEOR) on a platinum electrode, with a special emphasis on the role of the chemical properties of the anion present in the electrolyte composition. Essential knowledge of the mechanism and dynamics of glycerol electrooxidation is obtained through comprehensive studies that involve in sit...
The application of mixed catalysts in chemical to electrical energy transformation reactions can be a strategy for enhancing the catalysis of these reactions. Platinum and palladium exhibit significant catalytic activity...
In this review, recent advances in the use of platinum single-crystal surfaces in electrochemistry are addressed. The starting point is the voltammetric characterization in a supporting electrolyte because the profile can be used as a fingerprint of the surface, allowing the surface quality and solution cleanliness to be established. The signals ap...
In the present paper, the influence of electrogenerated (110) defects in the methanol oxidation reaction (MOR) on a Pt(111) electrode has been studied. It is shown that methanol oxidation is favored at the defected surfaces as evidenced by the displacement of the onset potential to lower values and the increase of the peak current density. The curr...
The rate of CO formation from CO2 reduction on Pt(111) vicinal surfaces containing (100) steps, Pt(S)[n(111) × (100)], has been investigated using cyclic voltammetry. To obtain further information about the different roles of terrace and step atoms in this reaction, selective modification of step sites with either bismuth or copper has been perform...
An autonomous electrochemical system prototype for ammonia oxidation reaction (AOR) measurements was efficiently done inside a 4'' x 4'' x 8'' 2U Nanoracks module at the International Space Station (ISS). This device, the Ammonia Electrooxidation Lab at the ISS (AELISS), included an autonomous electrochemical system that complied with NASA ISS nond...
The behaviour of CTAB adsorbed on polycrystalline gold electrodes has been studied using a combination of spectroelectrochemical methods. The results indicate that the formation of the layer is the consequence of the precipitation of the CTAB micelles on the electrode surface as bromide ions, which stabilize the micelles, are replaced by perchlorat...
Isopropanol oxidation is studied on platinum single crystals using electrochemical techniques and FTIR spectroscopy at different isopropanol concentrations. Isopropanol oxidation is found to be facilitated by the presence of adsorbed OH on the electrode surface, which reacts with an isopropanol molecule to yield the adsorbed alkoxide. Thus, when su...
A detailed mechanism for the electrooxidation of formic acid on platinum is presented. The mechanism is based on experimental results obtained with different techniques in combination with theoretical computations. Despite the apparent simplicity of the reaction, the oxidation mechanism of formic acid has two well-defined paths, one going through a...
The characterization of Pt single crystals surfaces decorated with adsorbed adatoms from the p-block is illustrated here. The main techniques for the decoration of Pt single crystals are under potential deposition (UPD) and irreversible adsorption. Several surface characterization techniques are available and have been proven to be complementary fo...
The use of decorated well-defined Pt single crystal model electrodes modified with adatoms is the optimum way to systematically study the surface structure–composition–catalytic activity correlations. In this review, we have focused on the most relevant works carried out on modified Pt single crystals for widely studied anodic reactions in fuel cel...
Platinum nanoparticles are indispensable in electrochemical applications, e.g., for the generation and usage of green hydrogen. Therefore, understanding the properties of these materials before and during operation is a crucial...
Electrochemical stripping voltammetry electroanalysis sensitivity and selectivity are oftentimes limited by wide
variance in analyte electrode surface adsorption and desorption
energies. The use of highly oriented Au(111) single crystal and thin
film surfaces is shown to decrease this variance and improve
detection for arsenic (As) in water. Cyclic...
Although the oxygen reduction reaction (ORR) involves multiple proton-coupled electron transfer processes, early studies reported the absence of kinetic isotope effects (KIEs) on polycrystalline platinum, probably due to the use of unpurified D2O. Here we developed a methodology to prepare ultra-pure D2O, which is indispensable for reliably investi...
The study of the hydrogen evolution reaction (HER) aimed to reach a deeper understanding of the parameters that control the rate of this reaction is of great importance given the technical relevance of hydrogen production as an energy vector in the so-called hydrogen economy. In previous works, laser-induced temperature jump (LITJ) experiments on P...
Electrocatalytic activity is influenced by the surface charge on the solid catalyst. Conventionally, our attention has been focused on how the surface charge shapes the electric potential and concentration of ionic reactant(s) in the local reaction zone. Taking H2O2 redox reactions at Pt(111) as a model system, we reveal a peculiar surface charge e...
In the present paper, we have studied the influence of (bi)sulfate anion (0.1 and 0.5 M) on the electro-oxidation of glycerol on basal Pt(hkl) and stepped surfaces belonging to the series of Pt(S)[n(111) x (111)]. Cyclic voltammograms and derivative voltammetry pointed out that the catalytic activity decreases for Pt(111) and Pt(110) and, to a mino...
The electro-oxidation of glucose (0.01 M) in a neutral solution phosphate buffer solution – pH ∼7 (0.1 M) is strongly sensitive to the surface structure. On surfaces containing (100) terraces domains the reaction occurs mainly into these sites due to their higher activity. Higher (111) step density into (100) terrace domains conducts the reaction t...
The heterogeneous upgrading of biomass by means of electrocatalytic hydrogenation is an attractive way to refine products for industrial and pharmaceutical purposes. Also, the efficient electrochemical reduction of carbonyl compounds can act as hydrogen vectors, and therefore energy vectors. In this manuscript, we render further fundamental insight...
Ethanol fuel cells require selective catalysts for complete oxidation of the fuel, which involves C–C bond cleavage. From experiments on well-defined surfaces and calculations, the mechanism controlling the ethanol electro-oxidation selectivity on platinum in aqueous media as a model system is elucidated. Adsorbed OH favors ethanol adsorption and c...
The electrochemical behavior of hydrogen peroxide, which is a possible intermediate of the oxygen reduction reaction (ORR), has been investigated on platinum single crystal electrodes containing terraces with (111) symmetry separated by monoatomic steps with either (110) or (100) symmetry in different pH solutions [1]. On these electrodes, a decrea...
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 plac...
An autonomous electrochemical system prototype for ammonia oxidation reaction (AOR) measurements was efficiently done inside a 4" x 4" x 8" 2U Nanoracks module at the International Space Station (ISS). This system, the Ammonia Electrooxidation Lab at the ISS (AELISS), included an autonomous electrochemical system that complied with NASA ISS nondisc...
Narrow solar-light response range and rapid charges recombination are the main technical barriers in TiO2 photocatalysis technology. To overcome these restrictions, in this work we synthesized a novel binuclear gadolinium (III) coordination complex, [Gd2(DPDB)6(DMF)6(H2O)2] (DPDB = [(4-dimethylamino)phenyldiazenyl] benzenesulfonate), which was used...
Hydrogen energy-based electrochemical energy conversion technologies offer the promise of enabling a transition of the global energy landscape from fossil fuels to renewable energy. Here, we present a comprehensive review of the fundamentals of electrocatalysis in alkaline media and applications in alkaline-based energy technologies, particularly a...
The reasons for the sluggish kinetics of the hydrogen adsorption reaction in alkaline media remain still unkown. It is important to acquire information about the thermodynamic parameters characteristic of the different steps in the reaction. The hydrogen adsorption is a key step in the process of hydrogen evolution. Understanding the process of und...
Oxygen reduction reaction (ORR) was studied on {100}-oriented Pt nanoparticles with sizes 3 to 7 nm in sulphuric acid solution. The distribution and size of nanoparticles was analysed by transmission electron microscopy and metal loading was determined by inductively coupled plasma optical emission spectroscopy. The synthesised nanoparticles have a...
SO2 is a poisonous and anthropogenic gas generated by fossil fuel burning due to the common presence of S-containing contaminants in oil and coal. As a strategy to handle this pollutant and to increase H2 generation, the electrocatalytic SO2 oxidation reaction (SO2OR) is considered. In this way, SO2 is converted to H2SO4, while hydrogen gas is gene...
Tailoring electrocatalyst materials to the specific requirements of a certain reaction and to optimize activity or enhance selectivity is a key tactic for the development of low-temperature fuel and electrolyzer cells for clean energy production. Here, we demonstrate the modification of Cu(111) electrodes with different sub-monolayer coverages of f...
The hydrogen evolution reaction (HER) has been crucial for the development of fundamental knowledge on electrocatalysis and electrochemistry, in general. In alkaline media, many key questions concerning pH-dependent structure–activity relations and the underlying activity descriptors remain unclear. While the presence of Ni(OH)2 deposited on Pt(111...
In this work three mesoporous nitrogen-doped carbon support materials were evaluated for oxygen reduction reaction (ORR) in comparison to Vulcan carbon in 0.1 M KOH and 0.5 M H2SO4 solutions. Palladium nanoparticles were synthesised using citrate method and the average particle size of 3.9 ± 0.6 nm was obtained, which was determined from transmissi...
The interface between the Pt(111) surface and several MeF/HClO4 (Me⁺ = Li⁺, Na⁺, or Cs⁺) aqueous electrolytes is investigated by means of cyclic voltammetry and laser-induced temperature jump experiments. Results point out that the effect of the electrolyte on the interfacial water structure is different depending on the nature of the metal alkali...
The behavior of adsorbed CTAB and CTAOH on gold single crystal electrodes has been studied in solutions with different pH values. For the different single crystal electrodes, the adsorbed adlayer formed by CTA⁺ cations is in contact with the surface, when the electrode charge is negative. As the surface charge becomes positive, the adlayer detaches...
The use of shape-controlled nanomaterials represents an elegant way to improve the performance of many electrochemical reactions. However, two main aspects must be still optimised: decreasing particle size and increasing their activity. This study shows that the deposition of Pd on different small (3-5 nm) supported Pt materials (displaying a prefe...
In this work, we investigate the in-situ spectro-electrochemical behavior of Pt(110) electrodes in contact with acid solutions saturated with CO2. Similar to previous observations reported for Pt(111) electrodes, potential-dependent signals associated to adsorbed bicarbonate and carbonate anions are observed in the FT-IRRA spectra collected for Pt(...
The hydrogen peroxide reduction reaction (HPRR) is investigated at pH=13 on the Pt basal planes and stepped surfaces with (111) terraces separated by either monatomic (100) or (110) steps. A quantitative analysis of the surface structure effect revealed that Pt(111) is the most active surface and its activity progressively decreases when steps are...
In this work, in situ external infrared reflection absorption spectroscopy (IRRAS) is successfully employed for the detection of intermediate species in the oxygen reduction reaction (ORR) mechanism on a flat and well-defined Pt surface. Superoxide anion species (O2-) are detected on the Pt(111) surface in an O2-saturated solution with a NaF/HClO4...
The behavior of adsorbed CTAB on Au(111) electrodes has been studied using electrochemical and FTIR experiments in different aqueous solutions. The results show that the adsorbed layer is stable in acidic solutions in the whole potential range of study. The observed electrochemical and FTIR behavior is compatible with the formation of a membrane of...
Adsorbed amino acids can modulate the behavior of metal nanoparticles in advanced applications. Using a combination of electrochemical experiments, FTIR spectroscopy, and DFT calculations, glutamate species interacting with the Au(111) surface in solution are here investigated. Electrochemical results indicate that the adsorption behavior depends o...
Energy and economic data on gaseous biofuel production in microbial electrolysis cells (MECs) can guide their installation, operation mode and modelling. Hydrogen and methane production from waste mainly depends on...
All scientific reports regarding the electro-oxidation reaction of CO on Pt electrodes, without exception, show that this reaction is favored on Pt surfaces rich in defects. In fact, "ordinary"or simple CO preoxidation is a typical process of surface-defected catalysts obeying the conditions of a full COads layer formed at suitably low potentials,...
The use of single crystal electrodes as model catalysts has been widely applied for the study of several reactions. The known structure of the surface provides a system with controlled electronic properties that helps in the understanding of the mechanism of reactions. In this model system, any modification, including the adsorption of anions, orga...
Shape‐controlled metal nanoparticles are significantly improving the electrocatalysis of many relevant reactions. By controlling the shape of nanoparticles, it is possible to engineer their surface to exhibit a preferential structure. However, to facilitate the incorporation of shaped nanomaterials into practical electrochemical devices, it is indi...
Molecular understanding of the electrochemical oxidation of metals and the electro-reduction of metal oxides is of pivotal importance for the rational design of catalyst-based devices where metal(oxide) electrodes play a crucial role. Operando monitoring and reliable identification of reacting species, however, are challenging tasks because they re...
In this manuscript, the potential of zero charge (pzc) of platinum single-crystal electrodes has been determined using the impinging jet system and recording the transient associated with the interphase formation. Initially, the Pt(111), Pt(110), and Pt(100) electrodes covered with CO were used. To demonstrate the validity of the procedure, the val...
A detailed description of the Cu–electrolyte interface is vital to understand the electrocatalytic properties of Cu surfaces. Herein, we combine cyclic voltammetry and the laser-induced temperature jump technique to describe the structure of the Cu(111) and Cu(100) | electrolyte interfaces in 0.1 M NaOH in a glass-free electrochemical cell. The las...
The hydrogen evolution reaction is one of the most studied processes in electrochemistry and platinum is by far the best catalyst for this reaction. Despite the importance of this reaction on platinum, detailed and accurate kinetic measurements of the steps that lead to the main reaction are still lacking, particularly because of the fast rate of t...
Glucose is an important biomolecule that participates as a main source of energy in living organism reactions. Considering its biological importance, the electrochemical investigation about glucose electro-oxidation has attracted attention with the aim to develop non-enzymatic catalysts able to achieve the complete oxidation of glucose to be used a...
Platinum is a very effective electrode for the hydrogen evolution and oxidation reactions (HER/HOR) in acidic media. However, the activity for the HOR on platinum falls two orders of magnitude from acidic to alkaline media, which has not been completely understood yet. Here, we provide an explanation for that. Both the HER and the HOR were investig...
The most recent advances for the ORR in Pt single crystal electrodes are summarized. A mechanism for the reaction is presented in light of the recent results.
The application of shape-controlled metal nanoparticles in Electrocatalysis has improved significantly the activity, selectivity, and even the stability of many relevant electrocatalytic reactions. It is well-accepted that, by controlling the shape of the nanoparticles, it is possible to provide nanoparticles with a preferential surface structure....
Knowledge of atomistic structures at solid/liquid interfaces is essential to elucidate interfacial processes in chemistry, physics, and materials sciences. The (√3 × √7) structure associated with a pair of sharp reversible current spikes in the cyclic voltammogram on a Au(111) electrode in sulfuric acid solution represents one of the most classical...
Reaction rates and mechanisms of most electrocatalytic reactions are known to critically depend on the structure of the electrode surface. Examples of structure sensitive electrocatalytic systems include the reduction of oxygen and the oxidation of small organic molecules on platinum, for instance. Even more intricate is the effect of the interfaci...
In this work, the oxygen reduction reaction (ORR) on tellurium-modified Pt(111) surfaces has been studied. Adsorption of Te adatoms on Pt(111) progressively shifts toward less positive values of both the ORR reaction onset and the half-wave potential in 0.1M HClO4 for 0 < θTe < 0.25. However, at θTe > 0.25, the ORR activity increases relative to th...
The electrochemical behavior of platinum single crystal surfaces can be taken as a model response for the interpretation of the activity of heterogeneous electrodes. The cyclic voltammogram of a given platinum electrode can be considered a fingerprint characteristic of the distribution of sites on its surface. We start this review by providing some...
The interfacial properties of platinum single crystal electrodes in contact with alkaline aqueous solutions (pH = 13) have been investigated using the laser induced temperature jump method. This technique offers insights into the net orientation of water dipoles in contact with the electrode surface by recording the coulostatic potential changes af...
The hydrogen peroxide reduction reaction (HPRR) is investigated on Pt(111) as well as on Pt(S)[(n-1)(111) × (110)] and Pt(S)[n(111) × (100)] stepped surfaces in 0.1 M HClO4 by means of voltammetric studies using the hanging meniscus rotating disk electrode (HMRDE) configuration. Results point out that there is a direct correlation between the poten...
Advanced applications of colloidal nanoparticles (NPs) become to depend on their specific shape, which is controlled by the adsorption behavior of the capping agent involved in their synthesis. To understand the way in which citric acid determines the shape of gold NPs, the adsorption behavior of citrate on gold under the synthesis conditions is he...
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 specif...
The study of the oxygen reduction reaction (ORR) at high-index Pt(hkl) single crystal surfaces has received considerable interest due to their well-ordered, typical atomic structures and superior catalytic activities. However, it is difficult to obtain direct spectral evidence of ORR intermediates during reaction processes, especially at high-index...
The site geometry preference of CO binding on stepped Pt single crystals in alkaline solution was investigated by in situ FTIR spectroscopy. The surfaces of the Pt single crystals consisted of different width (111) terraces, interrupted by (110) or (100) monoatomic steps. Experiments carried out with CO adsorbed exclusively on the top of the steps...
In situ electrochemical infrared and Raman spectroscopy are powerful tools for probing potential-dependent adstructures at solid/liquid electrochemical interfaces. However, it is very difficult to quantitatively interpret the observed spectral features including potential-dependent vibrational frequency and spectral intensity, even from model syste...
In the field of the catalysis on solid surfaces, discrimination of the site-specific chemistry taking place on surfaces consisting of multiple types of sites is challenging, especially at electrified solid/liquid interfaces. In this study, site-specific chemical labeling on Pt stepped surfaces was achieved by attaching the 13CO species exclusively...
The electrochemical reduction of nitrate anions in aqueous 0.1 M perchloric acid has been studied using Pt(S)-[n{1 1 0} × {1 1 1}] and Pt(S)-[n{1 1 0} × {1 0 0}] single crystal electrodes. It is demonstrated that the presence of Pt{1 1 0} adsorption sites is associated with a single, broad nitrate reduction peak centred at 0.18 V (RHE). Moreover, d...
The pKa of bicarbonate ion adsorbed on the surface of Pt(111), HCO3⁻(ads), in CO2 -saturated KClO4/HClO4 aqueous solutions has been determined by judicious application of a theoretical model originally proposed by Smith and White (Langmuir 1993, 9 (1), 1–3) to explain voltammetric features found for non-redox active alkyl chain monolayers bearing c...
INTRODUCTION
Efforts in our laboratories have been focused on the rational design and assembly of bifunctional electrocatalytic interfaces incorporating two electrocatalysts acting in series as a means of improving both the overall activity and specificity of redox processes involving multiple transfer of electrons. This strategy was recently imple...
Au surfaces modified by Pd electrodeposits have been found to enhance the rates of nitrate electroreduction in acidic aqueous solutions containing Cd²⁺ over those of the bare Au substrate in the same media. Rather surprisingly, similar electrocatalytic effects were also observed for ensembles of Au and Pd nanoparticles supported on otherwise inert...
Nanoparticles are essential electrocatalysts in chemical production, water treatment and energy conversion, but engineering efficient and specific catalysts requires understanding complex structure–reactivity relations. Recent experiments have shown that Bragg coherent diffraction imaging might be a powerful tool in this regard. The technique provi...
The search for new surface sensitive probes that characterize the surface structure of shape and size-controlled nanoparticles is an interesting topic to properly understand the correlations between electrocatalytic properties and surface structure at the nanoscale. Herein, we report the use of Cu UPD to characterize, not only qualitatively but als...
The surface modification of electrodes attracts great interest in electrocatalysis. It has often been observed that deposition of foreign adatoms on the surface of an electrode can originate a significant enhancement in the catalytic activity. For example, it has been reported that nickel deposits on Pt surfaces improve the rate of the hydrogen evo...
