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July 2013 - present
Publications
Publications (64)
Achieving the optimal balance between cost-efficiency and stability of oxygen reduction reaction (ORR) catalysts is currently among the key research focuses aiming at reaching a broader implementation of proton-exchange membrane fuel cells (PEMFCs). To address this challenge, we combine two well-established strategies to enhance both activity and s...
Designing electrocatalysts with optimal activity and selectivity relies on a thorough understanding of the surface structure under reaction conditions. In this study, experimental and computational approaches are combined to elucidate reconstruction processes on low‐index Pd surfaces during H‐insertion following proton electroreduction. While elect...
Platinum-liquid electrolyte interfaces are one of the most studied in electrochemistry. Still, until very recently, knowledge of the interfacial changes during platinum oxidation and reduction remained elusive. This information is crucial for any electrochemical applications in which platinum is used as a catalyst as it allows its more economical u...
Hydrogen-fuelled proton-exchange membrane fuel cells (PEMFCs) offer a promising path towards zero-emission energy, but their commercialization is hindered by challenges, particularly in the cathode catalysts responsible for the oxygen reduction reaction (ORR). Current catalysts rely heavily on expensive platinum, which degrades quickly in the harsh...
Renewable energy technologies increasingly rely on electrochemical energy conversion technologies in which oxygen evolution reaction (OER) is the main reaction on the anode. To improve the economic feasibility of such technologies, a thorough understanding of iridium's dissolution under operational conditions, including different pHs, is essential,...
Iridium's exceptional stability and catalytic properties make it indispensable in a wide range of electrochemical applications. Nevertheless, despite its importance, the full extent of its dissolution behavior under various conditions is still poorly understood. To fill this knowledge gap, this study uses online inductively coupled plasma mass spec...
The electrochemical applications of gold span the entire pH spectrum. Recently, gold dissolution in acidic and alkaline media has been studied, but less attention has been given to electrolytes at intermediate pH values. To address this gap, this work uses on‐line electrochemical dissolution inductively coupled plasma mass spectrometry (ICP‐MS) to...
Electrocatalysts design has been an important researching discipline in the filed of electrochemical energy conversion and storage, among which, surface (organic) modification has becoming an efficient, selective, and flexible approach in electrocatalysis study and applications. In the focus of direct modulation on electrocatalysis interfaces, the...
Pt plays a leading role in electrocatalysis, being the best pure metal catalyst for the oxygen reduction reaction (ORR) taking place at the cathode of the commercial polymer electrolyte membrane fuel cells (PEMFCs). In addition, it is usually used in the cathode to catalyze the hydrogen evolution reaction (HER) in water electrolyzers for hydrogen p...
Widespread adoption of advanced energy technologies, such as proton-exchange membrane fuel cells (PEMFCs), relies on the development of efficient and durable electrocatalysts for the oxygen reduction reaction (ORR). Given its unique properties, platinum has been the exclusive option for meeting activity demands, whether in its monometallic form or...
Understanding the mechanisms of Pt dissolution with well‐defined surfaces is vital for developing stable catalysts for electrochemical energy conversion devices such as fuel cells. This work investigates Pt dissolution from low‐index single crystals in perchlorate, sulfate, and methanesulfonate acid solutions by on‐line inductively coupled plasma m...
Global demand for more effective methods to reclaim gold from electronic waste (E‐waste) has never been greater. Alternatives to hydrometallurgical methods, such as cyanide, are still limited. This work examines utilizing ozone and chlorides to recycle Au from E‐waste. It is started with a fundamental investigation of Au dissolution processes on th...
Platinum electrocatalysts are still widely used as cathode material in proton-exchange membrane fuel cells (PEMFC) because of their high ORR activity. However, their long-term stability is limited due to degradation processes. This degradation is partly caused by Pt oxidation and oxide reduction, which lead to irreversible surface restructuring and...
The scarcity of iridium, needed to catalyze the sluggish oxygen evolution reaction (OER), hinders large-scale hydrogen production with proton exchange membrane water electrolyzers (PEMWEs). Crucial steps require reducing its loading while improving its overall activity and stability. Despite knowledge transfer challenges, cost and time constraints...
Ag-based electrocatalysts are promising candidates to catalyze the sluggish oxygen reduction reaction (ORR) in anion exchange membrane fuel cells (AEMFC) and oxygen evolution reaction (OER) in unitized regenerative fuel cells. However, to be competitive with existing technologies, the AEMFC with Ag electrocatalyst must demonstrate superior performa...
The degradation of Pt‐containing oxygen reduction catalysts for fuel cell applications is strongly linked to the electrochemical surface oxidation and reduction of Pt. Here, we study the surface restructuring and Pt dissolution mechanisms during oxidation/reduction for the case of Pt(100) in 0.1 M HClO4 by combining operando high‐energy surface X‐r...
The degradation of Pt‐containing oxygen reduction catalysts for fuel cell applications is strongly linked to the electrochemical surface oxidation and reduction of Pt. Here, we study the surface restructuring and Pt dissolution mechanisms during oxidation/reduction for the case of Pt(100) in 0.1 M HClO 4 by combining operando high‐energy surface X‐...
The first step of electrochemical surface oxidation is extraction of a metal atom from its lattice site to a location in a growing oxide. Here we show by fast simultaneous electrochemical and in situ high-energy surface X-ray diffraction measurements that the initial extraction of Pt atoms from Pt(111) is a fast, potential-driven process, whereas c...
Liquid fuels are considered a promising alternative to hydrogen in proton exchange membrane fuel cells. In particular, isopropanol, which can be selectively oxidised to acetone and further hydrogenated back to isopropanol using electrochemical and heterogeneous catalysis routes, respectively, opens the possibility of zero-emission fuel cell operati...
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...
The development of sustainable electrocatalysts is essential for promoting anion exchange membrane water electrolysis technology (AEMWE). Ni-Mo and MoO2 materials have enhanced alkaline hydrogen evolution reaction (HER) activity. This study...
Stabilization of cathode catalysts in hydrogen-fueled proton-exchange membrane fuel cells (PEMFCs) is paramount to their widespread commercialization. Targeting that aim, Pt-Au alloy catalysts with various compositions (Pt95Au5, Pt90Au10, and Pt80Au20) prepared by magnetron sputtering were investigated. The promising stability improvement of the Pt...
The concentration dependence of the activity for the oxidation of formic acid at pH 1.2, 2.4, and 3.9 has been studied on Pt(1 1 1), Pt(1 0 0), and stepped Pt[n(1 1 1) × (1 1 0)] electrodes. The results clearly demonstrate that, in this pH range, formate, and not formic acid, is the active species. To analyse the data, a kinetic model in which adso...
Replacing fossil fuels with renewable energy sources is one of the most challenging tasks in today's society. As renewable sources are intermittent in nature, a promising solution is to store the produced energy in the form of hydrogen, which can be produced electrochemically by using proton exchange membrane water electrolyzers (PEMWEs). A limitin...
Gold is often employed in nanotechnology to develop biosensors and new drug delivery and cancer therapy strategies. Since these applications are used in physiological pH, understanding the stability of gold in a broader pH range including neutral values will provide an useful insight into how to expand the use of gold safely.
By using buffer soluti...
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 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...
In the last years, polymer electrolyte membrane fuel cell (PEMFC) technology has progressed notably, allowing its extended implementation in the transport sector. For example, the fuel cell cars currently being commercialized use PEMFCs with Pt nanoparticles for the oxygen reduction reaction (ORR) at the cathode, primarily because of their better l...
Dissolution and redeposition processes determine the stability of electrode materials. In this work, we address these processes in situ during oxidation and subsequent reduction of Au(111) electrodes in an acidic electrolyte (0.1 M H2SO4). We used complementary techniques, namely, electrochemical scanning tunneling microscopy (EC-STM) and on-line i...
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...
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...
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...
We report a study using Pt(111) and Pt(100) electrodes of the role of adsorbed formate in both the direct and indirect pathways of the electrocatalytic oxidation of formic acid. Cyclic voltammetry at different concentrations of formic acid and different scan rates, as well as pulsed voltammetry, were used to obtain a deeper insight into the effect...
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.
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 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...
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...
Interfacial charge has a decisive influence on the reactivity of the most common electrochemical reactions for practical applications. In this work, the concepts of surface charge and the different types of potential of zero charge (pzc) are revised on model electrodes. The different methodologies for the determination of the pzc are reviewed. Afte...
The adsorption and reactivity of acetonitrile (CH3CN) have been studied on Pt(111) and Pt(100) electrodes in 0.1 M HClO4 and 0.1 M NaOH solutions with CH3CN concentrations ranging from 10-3 M to 1 M. Cyclic voltammetry results show that these processes are structure sensitive and that the hydrogen adsorption/desorption region is partially blocked o...
Developing an understanding of structure–activity relationships and reaction mechanisms of catalytic processes is critical to the successful design of highly efficient catalysts. As a fundamental reaction in fuel cells, elucidation of the oxygen reduction reaction (ORR) mechanism at Pt(hkl) surfaces has remained a significant challenge for research...
The formic acid oxidation reaction has been studied on Pt(111), Pt(100) and Pt nanoparticles with preferential (111) surface structure in 0.1 M HClO4 in the presence of different concentrations of acetonitrile. An electrocatalytic enhancement towards the formic acid oxidation has been observed under these conditions, and it is proposed that this en...
Oxygen reduction reaction (ORR) is studied on Pt(111) in the presence of different concentrations of bromide anions at different pH values ranging from very acidic to neutral solutions. While adsorbed bromide inhibits the ORR, the strength of the inhibition decreases when the pH is increased. This is a consequence of the lower relative adsorption e...
Bromide adsorption on Pt(111) is investigated by means of cyclic voltammetry and CO displacement experiments at different pH values. In acidic pH bromide adsorption is strongly overlapped with hydrogen desorption process. However, as the pH increases, hydrogen adsorption process displaces towards negative potentials while bromide adsorption remains...
In this communication, we will present recent results on the oxygen reduction reaction (OOR) on nitrogen doped carbons. DFT calculations on nitrogen doped graphene systems will be used to understand the key elements that activate the reaction on these materials. The study is centered on the monodentate chemisorption of molecular oxygen as the first...
The hydrogen peroxide reduction reaction (HPRR) on Pt(111) has been studied for the first time in acid to neutral pH values in the absence of anion specific adsorption using the HMRDE configuration. The onset for the reduction is ca. 0.95 V (RHE) for the Pt(111), irrespective of the pH value. At more negative potential values, the reduction is inhi...
The oxygen reduction reaction (ORR) at different pH values has been studied at platinum single crystal electrodes using the hanging meniscus rotating disk electrode (HMRDE) configuration. The use of NaF/HClO4 mixtures allows investigating the reaction up to pH = 6 in solutions with enough buffering capacity and in the absence of anion specific adso...
In order to produce hydrogen peroxide in small-scale electrochemical plants, selective catalysts for the oxygen reduction reaction (ORR) toward the desired species are required. Here, we report about the synthesis, characterization, ORR electrochemical behavior, and reaction mechanism of an aza-fused π-conjugated microporous polymer, which presents...
The borohydride oxidation reaction on platinum single-crystal electrodes has been studied in sodium hydroxide solution using static and rotating conditions. The results show that borohydride electro-oxidation is a structure sensitive process on Pt surfaces. Significant changes in the measured currents are observed at low potentials. In this region,...
