| 1. |
- B. Araujo, Rafael, et al.
(författare)
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Elucidating the role of Ni to enhance the methanol oxidation reaction on Pd electrocatalysts
- 2020
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Ingår i: Electrochimica Acta. - : Elsevier BV. - 0013-4686 .- 1873-3859. ; 360
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Tidskriftsartikel (refereegranskat)abstract
- Amongst promising available technologies enabling the transition to renewable energy sources, electrochemical oxidation of alcohols, in a direct fuel cell or in an electrolysis reaction (H-2 production), can be an economically and sustainable alternative to currently used technologies. In this work, we highlight the advantages of a Pd-Ni bimetallic electrocatalyst for methanol electrooxidation - a convenient choice due to the low cost of Ni combined with the observed acceptable catalytic performance of Pd. We report a synergistic effort between experiments and theoretical calculations based on density functional theory to provide an in-depth understanding - at the atomistic level - of the origin of the enhanced electrochemical activity of methanol electrooxidation using the bimetallic catalysts Pd3Ni and PdNi over pure Pd. Cyclic voltammograms and High-Performance Liquid Chromatography (HPLC) demonstrate higher activity towards methanol electrooxidation with increased Ni concentration and, furthermore, higher selectivity for CO2. These effects are understood by: 1) changes in the methanol oxidation reaction mechanism. 2) Mitigation or suppression of CO poisoning on the Pd-Ni alloys as compared to the pure Pd catalyst. 3) A stronger tendency towards highly oxidized intermediates for the alloys. These findings elucidate the effects of a bimetallic electrocatalyst for alcohol electrooxidation as well as unambiguously suggest PdNi as a more cost-effective alternative electrocatalyst.
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| 2. |
- Martín-Yerga, Daniel, et al.
(författare)
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Correlative Voltammetric Microscopy: Structure-Activity Relationships in the Microscopic Electrochemical Behavior of Screen Printed Carbon Electrodes.
- 2019
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Ingår i: ACS Sensors. - : American Chemical Society (ACS). - 2379-3694.
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Tidskriftsartikel (refereegranskat)abstract
- Screen-printed carbon electrodes (SPCEs) are widely used for electrochemical sensors. However, little is known about their electrochemical behavior at the microscopic level. In this work, we use voltammetric scanning electrochemical cell microscopy (SECCM), with dual-channel probes, to determine the microscopic factors governing the electrochemical response of SPCEs. SECCM cyclic voltammetry (CV) measurements are performed directly in hundreds of different locations of SPCEs, with high spatial resolution, using a sub-µm sized probe. Further, the localized electrode activity is spatially-correlated to co-located surface structure information from scanning electron microscopy and micro-Raman spectroscopy. This approach is applied to two model electrochemical processes: hexaammineruthenium (III/II) ([Ru(NH3)6]3+/2+), a well-known outer-sphere redox couple; and dopamine (DA) which undergoes a more complex electron-proton coupled electro-oxidation, with complications from adsorption of both DA and side-products. The electrochemical reduction of [Ru(NH3)6]3+ proceeds fairly uniformly across the surface of SPCEs on the sub-µm scale. In contrast, DA electro-oxidation shows a strong dependence on the microstructure of the SPCE. By studying this process at different concentrations of DA, the relative contributions of (i) intrinsic electrode kinetics and (ii) adsorption of DA are elucidated in detail, as a function of local electrode character and surface structure. These studies provide major new insights on the electrochemical activity of SPCEs and further position voltammetric SECCM as a powerful technique for the electrochemical imaging of complex, heterogeneous and topographically rough electrode surfaces.
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| 3. |
- Martín-Yerga, Daniel, et al.
(författare)
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Effects of Incorporated Iron or Cobalt on the Ethanol Oxidation Activity of Nickel (Oxy)Hydroxides in Alkaline Media
- 2019
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Ingår i: Electrocatalysis. - : Springer Science and Business Media LLC. - 1868-2529 .- 1868-5994.
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Tidskriftsartikel (refereegranskat)abstract
- Nickel (oxy)hydroxides (NiOxHy) are promising cost-effective materials that exhibit a fair catalytic activity for the ethanol oxidation reaction (EOR) and could be used for sustainable energy conversion. Doping the NiOxHy structure with other metals could lead to enhanced catalytic properties but more research needs to be done to understand the role of the doping metal on the EOR. We prepared NiOxHy films doped with Fe or Co with different metallic ratios by electrodeposition and evaluated the EOR. We found a positive and negative effect on the catalytic activity after the incorporation of Co and Fe, respectively. Our results suggest that Ni atoms are the active sites for the EOR since Tafel slopes were similar on the binary and pristine nickel (oxy)hydroxides and that the formal potential of the Ni(II)/Ni(III) redox couple is a good descriptor for the EOR activity. This work also highlights the importance of controlled metal doping on catalysts and may help in the design and development of improved materials for the EOR.
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| 4. |
- Martín-Yerga, Daniel
(författare)
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Electrochemical Detection and Characterization of Nanoparticles with Printed Devices
- 2019
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Ingår i: Biosensors. - : MDPI AG. - 2079-6374. ; 9:2
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Forskningsöversikt (refereegranskat)abstract
- Innovative methods to achieve the user-friendly, quick, and highly sensitive detection of nanomaterials are urgently needed. Nanomaterials have increased importance in commercial products, and there are concerns about the potential risk that they entail for the environment. In addition, detection of nanomaterials can be a highly valuable tool in many applications, such as biosensing. Electrochemical methods using disposable, low-cost, printed electrodes provide excellent analytical performance for the detection of a wide set of nanomaterials. In this review, the foundations and latest advances of several electrochemical strategies for the detection of nanoparticles using cost-effective printed devices are introduced. These strategies will equip the experimentalist with an extensive toolbox for the detection of nanoparticles of different chemical nature and possible applications ranging from quality control to environmental analysis and biosensing.
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| 5. |
- Martín-Yerga, Daniel, et al.
(författare)
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In situ catalyst reactivation for enhancing alcohol electro-oxidation and coupled hydrogen generation
- 2020
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Ingår i: Chemical Communications. - : Royal Society of Chemistry (RSC). - 1359-7345 .- 1364-548X. ; 56:28, s. 4011-4014
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Tidskriftsartikel (refereegranskat)abstract
- A novel method exploiting the in situ reactivation of a PdNi catalyst to enhance the electro-oxidation of alcohols is reported. The periodic regeneration of the catalyst surface leads to significant gains in terms of conversion rate, energy requirements and stability compared to the conventional potentiostatic method.
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| 6. |
- Martín-Yerga, Daniel, et al.
(författare)
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In Situ Spectroelectrochemical Monitoring of Dye Bleaching after Electrogeneration of Chlorine-Based Species : Application to Chloride Detection
- 2018
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Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 90:12, s. 7442-7449
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Tidskriftsartikel (refereegranskat)abstract
- Spectroelectrochemical techniques are becoming increasingly versatile tools to solve a diverse range of analytical problems. Herein, the use of in situ real-time luminescence spectroelectrochemistry to quantify chloride ions is demonstrated. Utilizing the bleaching effect of chlorine-based electrogenerated products after chloride oxidation, it is shown that the fluorescence of the rhodamine 6G dye decreases proportionally to the initial chloride concentration in solution. A strong decrease of fluorescence is observed in acidic media compared to a lower decrease in alkaline media, which suggests that Cl-2, favorably generated at low pH, could be the main species responsible for the fluorescence loss. This fact is corroborated with chronoamperometric measurements where the complete loss of fluorescence for the bulk solution is achieved. A fast mass transfer is needed to explain this behavior, in agreement with the generation of gaseous species such as Cl-2. Chloride detection was performed in artificial sweat samples in less than 30 s with great accuracy. This electrochemical/optical combined approach allows us to quantify species that are difficult to measure by electrochemistry due to the inadequate resolution of their redox processes or being without significant optical properties.
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| 7. |
- Martin-Yerga, Daniel, et al.
(författare)
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Insights on the ethanol oxidation reaction at electrodeposited PdNi catalysts under conditions of increased mass transport
- 2021
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Ingår i: International journal of hydrogen energy. - : Elsevier BV. - 0360-3199 .- 1879-3487. ; 46:2, s. 1615-1626
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Tidskriftsartikel (refereegranskat)abstract
- The development of high-performance electrocatalysts for alcohol oxidation is still a major challenge to use these reactions for sustainable energy applications such as hydrogen production. In addition, understanding the reactivity under different hydrodynamic conditions is essential since the fuel is continuously fed to the anode in practical applications. In this work, the synthesis, characterization and electroactivity of bimetallic PdNi nano-coatings generated by electrodeposition toward the ethanol oxidation reaction (EOR) is described. A catalyst formed by Pd0.91Ni0.09 nanoflowers showed the highest EOR activity and enhanced performance under moderate mass transport rate. Both OH- concentration and hydrodynamics affected the EOR activity and the product selectivity. Acetic acid was the main EOR product, but acetaldehyde formation increased when OH- was limiting or under faster mass transport rates. This study provides novel knowledge to understand the EOR on PdNi catalysts and exposes the importance of evaluating hydrodynamic conditions when developing new electrocatalysts.
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| 8. |
- Martín-Yerga, Daniel, et al.
(författare)
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Structure–Reactivity Effects of Biomass-based Hydroxyacids for Sustainable Electrochemical Hydrogen Production
- 2021
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Ingår i: ChemSusChem. - : Wiley. - 1864-5631 .- 1864-564X. ; 14:8, s. 1902-1912
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Tidskriftsartikel (refereegranskat)abstract
- Biomass electro-oxidation is a promising approach for the sustainable generation of H2 by electrolysis with simultaneous synthesis of value-added chemicals. In this work, the electro-oxidation of two structurally different organic hydroxyacids, lactic acid and gluconic acid, was studied comparatively to understand how the chemical structure of the hydroxyacid affects the electrochemical reactivity under various conditions. It was concluded that hydroxyacids such as gluconic acid, with a considerable density of C−OH groups, are highly reactive and promising for the sustainable generation of H2 by electrolysis at low potentials and high conversion rates (less than −0.15 V vs. Hg/HgO at 400 mA cm−2) but with low selectivity to specific final products. In contrast, the lower reactivity of lactic acid did not enable H2 generation at very high conversion rates (<100 mA cm−2), but the reaction was significantly more selective (64 % to pyruvic acid). This work shows the potential of biomass-based organic hydroxyacids for sustainable generation of H2 and highlights the importance of the chemical structure on the reactivity and selectivity of the electro-oxidation reactions.
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| 9. |
- Martín-Yerga, Daniel, et al.
(författare)
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Towards single-molecule : In situ electrochemical SERS detection with disposable substrates
- 2018
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Ingår i: Chemical Communications. - : Royal Society of Chemistry. - 1359-7345 .- 1364-548X. ; 54:45, s. 5748-5751
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Tidskriftsartikel (refereegranskat)abstract
- Dynamic time-resolved Raman spectroelectrochemistry demonstrates the strong influence of nanostructuring and surface charge of in situ activated disposable substrates for SERS detection. Under specific conditions, a large enhancement factor and estimated calculations agree with the feasible detection of only a few molecules, approaching the limit of single-entity detection.
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| 10. |
- Pereira da Silva Neves, Marta Maria, et al.
(författare)
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Advanced Nanoscale Approaches to Single-(Bio)entity Sensing and Imaging
- 2018
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Ingår i: Biosensors. - : MDPI. - 2079-6374. ; 8:4
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Forskningsöversikt (refereegranskat)abstract
- Individual (bio)chemical entities could show a very heterogeneous behaviour under the same conditions that could be relevant in many biological processes of significance in the life sciences. Conventional detection approaches are only able to detect the average response of an ensemble of entities and assume that all entities are identical. From this perspective, important information about the heterogeneities or rare (stochastic) events happening in individual entities would remain unseen. Some nanoscale tools present interesting physicochemical properties that enable the possibility to detect systems at the single-entity level, acquiring richer information than conventional methods. In this review, we introduce the foundations and the latest advances of several nanoscale approaches to sensing and imaging individual (bio)entities using nanoprobes, nanopores, nanoimpacts, nanoplasmonics and nanomachines. Several (bio)entities such as cells, proteins, nucleic acids, vesicles and viruses are specifically considered. These nanoscale approaches provide a wide and complete toolbox for the study of many biological systems at the single-entity level.
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