Paula Macarena Abdala


Last Name

Abdala

First Name

Paula Macarena

ORCID

0000-0002-2011-1707

Organisational unit

03865 - Müller, Christoph R. / Müller, Christoph R.

Filters

2013 - 201992020 - 202557
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Publications 1 - 10 of 66
  • MgO-based sorbents promoted with alkali metal salts: formation of MgCO3 at the buried NaNO3-MgO interface investigated with in situ X-rays and electron microscopy
    Item type: Conference Poster
    Rekhtina, Margarita; Hansen Bork, Alexander; Willinger, Elena; et al. (2021)
  • Self-Terminated Surface Reconstruction of Lanthanum Nickelates Promotes Alkaline Oxygen Evolution
    Item type: Conference Poster
    Wu, Yi-Hsuan; Janák, Marcel; Abdala, Paula Macarena; et al. (2023)
    Oxygen evolution reaction (OER) itself is expected to have a strong impact on the state of the surface of the electrocatalyst, yet the actual structure of the surface under operating conditions is rarely considered while formulating structure-activity correlations in electrocatalysis. In this study, changes in the surface structure of Ruddlesden-Popper-type lanthanum nickelate, La2NiO4+δ, and the perovskite LaNiO3 are probed and contrasted using a series of complementary surface sensitive techniques, including XPS, HRTEM and O K-edge XAS. We found noticeable surface changes to occur on La2NiO4+δ after exposure its exposure to the alkaline electrolyte that is accompanied by the emergence of a strong Nin+/n+1 redox feature and the coincides with a 45-fold enhancement of the OER activity (at η = 370 mV) in 0.1 M KOH, as compared to the pristine La2NiO4+δ phase. We observe that the in situ formation of an amorphous nickel (oxy)hydroxide layer on the surface increases the electrochemically-active surface area of La2NiO4+δ and imparts a high stability of the catalyst under OER conditions (the formation of the amorphous layer self-terminates at ca. 3 nm). In addition, the transition from octahedral Ni sites (Oh) to square-planar Ni sites (D4h) in the reconstructed surface was observed using O K-edge X-ray absorption spectroscopy. Further, we found no evidence for any surface transformations in the perovskite-based catalyst LaNiO3 that also did not demonstrate any improvement in its activity over cycling. This work highlights the importance of a detailed surface analysis of the catalysts under operation to build robust structure-activity correlations for the metal oxides under electrochemical reaction conditions.
  • Electronic and geometric structure of Ce3+ forming under reducing conditions in shaped ceria nanoparticles promoted by platinum
    Item type: Journal Article
    Safonova, Olga V.; Guda, Alexander A.; Paun, Cristina; et al. (2014)
    The Journal of Physical Chemistry C
  • Boosting the CO2 uptake of MgO-Based Sorbents using Na2CO3 as Nucleation Seeds: Mechanistic Insights via In Situ Synchrotron XRD
    Item type: Other Conference Item
    Landuyt, Annelies; Kochetygov, Ilia; Krödel, Maximilian; et al. (2024)
    Abstract Book 2024 MRS Spring Meeting
  • Bulk and surface transformations of Ga2O3 nanoparticle catalysts for propane dehydrogenation induced by a H2 treatment
    Item type: Journal Article
    Castro-Fernández, Pedro; Mance, Deni; Liu, Chong; et al. (2022)
    Journal of Catalysis
    Three γ/β-Ga2O3 nanoparticle catalysts that differ in the relative ratio of γ-Ga2O3 to β-Ga2O3 were prepared to evaluate the effect of H2 treatment (500 °C, 2 h) on the coordination environment of bulk and surface Ga sites, Lewis acidity and catalytic activity in propane dehydrogenation (PDH). Independent of the H2 treatment, the initial PDH activity of the γ/β-Ga2O3 catalysts increases with the fraction of the β-Ga2O3 phase. This is explained by the presence of weak Lewis acid sites (LAS) in β-Ga2O3 while such sites are absent in γ-Ga2O3. Treatment with H2 increases the catalytic activity of all three γ/β-Ga2O3 catalysts but for different reasons. For catalysts with higher fractions of β-Ga2O3, H2 treatment increases further the relative abundance of weak LAS, likely by generating coordinatively unsaturated Ga sites (such as tricoordinated Ga sites nearby oxygen vacancies). In contrast, H2 treatment of a catalyst containing a predominant fraction of γ-Ga2O3 phase induces disorder in the sub-surface structure of the nanoparticle, that is, it forms gallium and oxygen vacancies in the bulk and favors migration of gallium, and likely also of oxygen, to the surface. This induces a surface reconstruction that notably increases the fraction of strong LAS (and proportionally decreases the fraction of medium LAS), while creating no weak LAS in γ-Ga2O3-H2. Therefore, the increase in the catalytic activity of H2-treated γ-Ga2O3 is explained by the higher density of surface Ga sites in γ-Ga2O3-H2 relative to calcined γ-Ga2O3. H2-treated catalysts that contain a higher relative amount of weak LAS also feature a higher relative abundance of gallium hydride species associated with a low frequency FTIR band at ca. 1931–1939 cm−1, that is, weak LAS likely give weakly-bound hydrides in β-Ga2O3. Our results highlight that weak LAS in unsupported Ga2O3 catalysts are more active in PDH than mild or strong LAS.
  • Probing the Local Structure of Na in NaNO₃-Promoted, MgO-Based CO₂ Sorbents via X-ray Absorption Spectroscopy
    Item type: Journal Article
    Rekhtina, Margarita; Bugaev, Aram; Dunstan, Matthew T.; et al. (2023)
    Chemistry of Materials
    This work provides insight into the local structure of Na in MgO-based CO2 sorbents that are promoted with NaNO3. To this end, we use X-ray absorption spectroscopy (XAS) at the Na K-edge to interrogate the local structure of Na during the CO2 capture (MgO + CO2 ↔ MgCO3). The analysis of Na K-edge XAS data shows that the local environment of Na is altered upon MgO carbonation when compared to that of NaNO3 in the as-prepared sorbent. We attribute the changes observed in the carbonated sorbent to an alteration in the local structure of Na at the NaNO3/MgCO3 interfaces and/or in the vicinity of [Mg2+···CO32–] ionic pairs that are trapped in the cooled NaNO3 melt. The changes observed are reversible, i.e., the local environment of NaNO3 was restored after a regeneration treatment to decompose MgCO3 to MgO. The ex situ Na K-edge XAS experiments were complemented by ex situ magic-angle spinning 23Na nuclear magnetic resonance (MAS 23Na NMR), Mg K-edge XAS and X-ray powder diffraction (XRD). These additional experiments support our interpretation of the Na K-edge XAS data. Furthermore, we develop in situ Na (and Mg) K-edge XAS experiments during the carbonation of the sorbent (NaNO3 is molten under the conditions of the in situ experiments). These in situ Na K-edge XANES spectra of molten NaNO3 open new opportunities to investigate the atomic scale structure of CO2 sorbents modified with Na-based molten salts by using XAS.
  • Dynamics of phase transitions in Na2TiO3 and its possible utilization as a CO2 sorbent: a critical analysis
    Item type: Journal Article
    Blanco, Maria V.; Abdala, Paula Macarena; Gennari, Fabiana; et al. (2021)
    Reaction Chemistry & Engineering
    Na-Based materials are emerging as promising high-temperature CO2 sorbents. In this work, we provide a detailed study on the synthesis of Na(2)TiO(3)via a solid-state route using NaOH and TiO2 as starting reactants. The CO2 sorption properties of the synthesized Na2TiO3 were evaluated by thermogravimetric analysis. A subsequent comprehensive study on the complex reaction mechanism of Na2TiO3 at high temperatures under carbonation conditions was performed via real time in situ synchrotron X-ray diffraction analysis. In situ experiments performed under different conditions revealed the occurrence of thermally-driven phase transitions derived from the structural instability of the material at high temperatures. These reactions could be differentiated from carbonation processes, allowing the proposal of a reaction mechanism of the material as a CO2 sorbent. The obtained results can explain the abnormal dynamic thermogram displayed by Na2TiO3 in the presence of CO2 within a temperature range that is of interest for practical applications and serve as a basis for evaluating the feasibility of using this material in CO2 capture schemes.
  • Single-Atom-Substituted Mo2CTx:Fe-Layered Carbide for Selective Oxygen Reduction to Hydrogen Peroxide: Tracking the Evolution of the MXene Phase
    Item type: Journal Article
    Kuznetsov, Denis; Chen, Zixuan; Abdala, Paula Macarena; et al. (2021)
    Journal of the American Chemical Society
    This work critically assesses the electrocatalytic activity, stability, and nature of the active phase of a two-dimensional molybdenum carbide (MXene) with single-atomic iron sites, Mo2CTx:Fe (Tx are surface terminating groups O, OH, and F), in the catalysis of the oxygen reduction reaction (ORR). X-ray absorption spectroscopy unequivocally confirmed that the iron single sites were incorporated into the Mo2CTx structure by substituting Mo atoms in the molybdenum carbide lattice with no other detectable Fe-containing phases. Mo2CTx:Fe, the first two-dimensional carbide with isolated iron sites, demonstrates a high catalytic activity and selectivity in the oxygen reduction to hydrogen peroxide. However, an analysis of the electrode material after the catalytic tests revealed that Mo2CTx:Fe transformed in situ into a graphitic carbon framework with dispersed iron oxyhydroxide (ferrihydrite, Fh) species (Fh/C), which are the actual active species. This experimental observation and the results obtained for the titanium and vanadium 2D carbides challenge previous studies that discuss the activity of the native MXene phases in oxygen electrocatalysis. Our work showcases the role of 2D metal carbides as precursors for active carbon-based (electro)catalysts and, more fundamentally, highlights the intrinsic evolution pathways of MXenes in electrocatalysis.
  • SiO2-Supported CoxPt1-x Nanoalloys for the Dry Reforming of Methane
    Item type: Conference Poster
    Niedbalka, David; Thommen, Luca; Abdala, Paula Macarena; et al. (2024)
Publications 1 - 10 of 66