75 results on '"Björn Wickman"'
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2. Electrochemical Approach for Advanced Flow Reactors via Additive Manufacturing of High Surface Area Ti‐6Al‐4V Anode
- Author
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Mohammad Reza Bilesan, Meghdad Yazdani, Asst. Prof. Mathilde Luneau, Dr. Gerard Montserrat‐Sisó, Assoc. Prof. Björn Wickman, and Prof. Eveliina Repo
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alkaline electrolysis ,anodic behavior ,dynamic impedance spectroscopy ,3D printing ,Ti-6Al-4V ,Industrial electrochemistry ,TP250-261 ,Chemistry ,QD1-999 - Abstract
Abstract Electrochemical processes use expensive noble metal‐based anodes which limit industrial implementation. In this study, a noble‐metal‐free Ti‐6Al‐4V anode is introduced in an advanced flow reactor. We demonstrate that the 3D additively manufactured electrode can provide a more projected surface area and facilitate anodic reactions under controlled electrolyte conditions. Alkaline NaOH and KOH electrolytes act as anodic electrolytes that are toxic compounds‐free and enable corrosion control. Impedance and voltammetry responses to electrochemical reactions are studied. The electrochemical active surface area of the 4 rods scaffold geometry is 42 times higher than a flat plate anode. Therefore, improved charge transfer is achieved in the flow reactor incorporating the 3D Ti‐6Al‐4V electrode due to the increased surface area and wettability. The structure of almost non‐conductive passivation on a flat plate anode is changed to unstable passivation due to the 3D scaffold structure. This enables effective charge transfer of 911 mA cm−2 at higher potentials up to 5 V for 1.5 m KOH in a non‐flow condition. Furthermore, a 1 m KOH solution delays metal ion dissolution from the anode surface by acting as a corrosion‐controlling medium. 3D Ti‐6Al‐4V is likely to be an affordable alternative anode in alkaline environmentally friendly electrochemical applications.
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- 2023
- Full Text
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3. Impact of Accelerated Stress Tests on the Cathodic Catalytic Layer in a Proton Exchange Membrane (PEM) Fuel Cell Studied by Identical Location Scanning Electron Microscopy
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Magnus Skoglundh, Linnéa Strandberg, Victor Shokhen, and Björn Wickman
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Materials Chemistry ,Electrochemistry ,Energy Engineering and Power Technology ,Chemical Engineering (miscellaneous) ,Electrical and Electronic Engineering - Published
- 2022
4. Mercury Removal from Concentrated Sulfuric Acid by Electrochemical Alloy Formation on Platinum
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Vera Roth, Julia Järlebark, Alexander Ahrnens, Jens Nyberg, Justin Salminen, Teodora Retegan Vollmer, and Björn Wickman
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General Medicine - Published
- 2023
5. Temperature and concentration dependence of the electrochemical PtHg4 alloy formation for mercury decontamination
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Björn Wickman, Emma Feldt, Julia Järlebark, Pontus K. G. Gustafsson, Nora Molander, Rasmus N. G. Svensson, Vera Roth, and Cristian Tunsu
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Filtration and Separation ,Analytical Chemistry - Published
- 2023
6. Core–shell and heterostructured silver–nickel nanocatalysts fabricated by γ-radiation induced synthesis for oxygen reduction in alkaline media
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Yi Yang, Gerard Montserrat-Sisó, Björn Wickman, Pavel Anatolyevich Nikolaychuk, and Inna L. Soroka
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Inorganic Chemistry - Abstract
To reach commercial viability for fuel cells, one needs to develop active and robust Pt-free electrocatalysts. Silver has great potential to replace Pt as the catalyst for the oxygen reduction reaction (ORR) in alkaline media due to its low cost and superior stability. However, its catalytic activity needs to be improved. One possible solution is to fabricate bimetallic nanostructures, which demonstrate a bifunctional enhancement in the electrochemical performance. Here, two types of bimetallic silver-nickel nanocatalysts, core-shells (Ag@NiO) and heterostructures (Ag/Ni), are fabricated using γ-radiation induced synthesis. The Ag@NiO nanoparticles consist of an amorphous, NiO layer as a shell and a facetted crystalline Ag particle as a core. Meanwhile, the Ag/Ni heterostructures comprise Ag particles decorated with Ni/Ni(oxy-hydro)-oxide clusters. Both materials demonstrate similar and increased alkaline ORR activity as compared to monometallic catalysts. It was revealed that the enhanced catalytic activity of the core-shells is mainly attributed to the electronic ligand effect. While in the Ag/Ni heterostructures, a lattice mismatch between the Ni-based clusters and Ag implies a significant lattice strain, which, in turn, is responsible for the increased activity of the catalyst. Also, the Ag/Ni samples exhibit good stability under operating conditions due to the existence of stable Ni
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- 2022
7. Cover Feature: Comparison of Oxygen Adsorption and Platinum Dissolution in Acid and Alkaline Solutions Using Electrochemical Quartz Crystal Microbalance (ChemElectroChem 22/2022)
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Linnéa Strandberg, Victor Shokhen, Mathilde Luneau, Göran Lindbergh, Carina Lagergren, and Björn Wickman
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Electrochemistry ,Catalysis - Published
- 2022
8. Comparison of Oxygen Adsorption and Platinum Dissolution in Acid and Alkaline Solutions Using Electrochemical Quartz Crystal Microbalance
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Linnéa Strandberg, Victor Shokhen, Mathilde Luneau, Göran Lindbergh, Carina Lagergren, and Björn Wickman
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Electrochemistry ,Catalysis - Published
- 2022
9. Plasma-Induced Heating Effects on Platinum Nanoparticle Size During Sputter Deposition Synthesis in Polymer and Ionic Liquid Substrates
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Rosemary Brown, Björn Lönn, Robin Pfeiffer, Henrik Frederiksen, and Björn Wickman
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Materials science ,chemistry.chemical_element ,Nanoparticle ,Surfaces and Interfaces ,Sputter deposition ,Condensed Matter Physics ,Platinum nanoparticles ,Article ,Catalysis ,chemistry.chemical_compound ,chemistry ,Chemical engineering ,Sputtering ,Ionic liquid ,Electrochemistry ,General Materials Science ,Particle size ,Platinum ,Spectroscopy - Abstract
Nanoparticle catalyst materials are becoming ever more important in a sustainable future. Specifically, platinum (Pt) nanoparticles have relevance in catalysis, in particular, fuel cell technologies. Sputter deposition into liquid substrates has been shown to produce nanoparticles without the presence of air and other contaminants and the need for precursors. Here, we produce Pt nanoparticles in three imidazolium-based ionic liquids and PEG 600. All Pt nanoparticles are crystalline and around 2 nm in diameter. We show that while temperature has an effect on particle size for Pt, it is not as great as for other materials. Sputtering power, time, and postheat treatment all show slight influence on the particle size, indicating the importance of temperature during sputtering. The temperature of the liquid substrate is measured and reaches over 150 °C during deposition which is found to increase the particle size by less than 20%, which is small compared to the effect of temperature on Au nanoparticles presented in the literature. High temperatures during Pt sputtering are beneficial for increasing Pt nanoparticle size beyond 2 nm. Better temperature control would allow for more control over the particle size in the future.
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- 2021
10. Tuning morphology, composition and oxygen reduction reaction (ORR) catalytic performance of manganese oxide particles fabricated by γ-radiation induced synthesis
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Yohannes Kiros, Björn Wickman, Yi Yang, Inna Soroka, Xiangyang Kong, Gerard Montserrat Siso, Axel Relefors, and Zhuofeng Li
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Solid-state chemistry ,Morphology (linguistics) ,Chemistry ,02 engineering and technology ,Electrolyte ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Electrochemistry ,01 natural sciences ,Redox ,0104 chemical sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Catalysis ,Biomaterials ,Colloid and Surface Chemistry ,Chemical engineering ,Radiolysis ,Composition (visual arts) ,0210 nano-technology - Abstract
A γ-radiation induced synthesis method is used to fabricate manganese oxide catalysts through both reduction and oxidation routes. It is shown that the morphology, composition and electrochemical performance of the produced manganese oxide particles can be tuned by altering the redox conditions. The catalysts prepared via radiolytic oxidation have a hollow spherical morphology, possess γ-MnO2 structure and show high catalytic activity for the complete four-electron reaction pathway of the oxygen reduction reaction (ORR) in alkaline electrolyte. Meanwhile, the catalysts synthesized via radiolytic reduction possess a rod-like morphology with a Mn3O4 bulk structure and favour the incomplete two-electron reaction pathway for ORR. The high catalytic activity of the manganese oxide synthesized via the oxidation route can be attributed to high electrochemical surface area and increased amount of Mn3+ on the surface as compared to those in the sample obtained via the reduction route.
- Published
- 2021
11. Solvent Effects for Methanol Electrooxidation on Gold
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Björn Wickman, Anders Hellman, and Mikael Valter
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Reaction mechanism ,Chemistry ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,chemistry.chemical_compound ,General Energy ,Chemical engineering ,Methanol ,Physical and Theoretical Chemistry ,Solvent effects ,0210 nano-technology ,Methanol fuel - Abstract
A detailed understanding of the methanol electrooxidation reaction mechanism is important for the further development of methanol fuel cells. By modeling the reaction on Au(111) using density funct...
- Published
- 2021
12. Hydrogen induced interface engineering in Fe2O3–TiO2 heterostructures for efficient charge separation for solar-driven water oxidation in photoelectrochemical cells
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Aadesh P. Singh, Anders Hellman, Björn Wickman, Richard Baochang Wang, Camilla Tossi, Ilkka Tittonen, Department of Electronics and Nanoengineering, Chalmers University of Technology, Aalto-yliopisto, and Aalto University
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Photocurrent ,Materials science ,Valence (chemistry) ,Hydrogen ,business.industry ,General Chemical Engineering ,Doping ,chemistry.chemical_element ,Heterojunction ,02 engineering and technology ,General Chemistry ,Photoelectrochemical cell ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Semiconductor ,chemistry ,Optoelectronics ,Reversible hydrogen electrode ,0210 nano-technology ,business - Abstract
Semiconductor heterostructure junctions are known to improve the water oxidation performance in photoelectrochemical (PEC) cells. Depending on the semiconductor materials involved, different kinds of junctions can appear, for instance, type II band alignment where the conduction and valence bands of the semiconductor materials are staggered with respect to each other. This band alignment allows for a charge separation of the photogenerated electron-hole pairs, where the holes will go from low-to-high valance band levels and vice versa for the electrons. For this reason, interface engineering has attracted intensive attention in recent years. In this work, a simplified model of the Fe2O3-TiO2 heterostructure was investigated via first-principles calculations. The results show that Fe2O3-TiO2 produces a type I band alignment in the heterojunction, which is detrimental to the water oxidation reaction. However, the results also show that interstitial hydrogens are energetically allowed in TiO2 and that they introduce states above the valance band, which can assist in the transfer of holes through the TiO2 layer. In response, well-defined planar Fe2O3-TiO2 heterostructures were manufactured, and measurements confirm the formation of a type I band alignment in the case of Fe2O3-TiO2, with very low photocurrent density as a result. However, once TiO2 was subjected to hydrogen treatment, there was a nine times higher photocurrent density at 1.50 V vs. the reversible hydrogen electrode under 1 sun illumination as compared to the original heterostructured photoanode. Via optical absorption, XPS analysis, and (photo)electrochemical measurements, it is clear that hydrogen treated TiO2 results in a type II band alignment in the Fe2O3-H:TiO2 heterostructure. This work is an example of how hydrogen doping in TiO2 can tailor the band alignment in TiO2-Fe2O3 heterostructures. As such, it provides valuable insights for the further development of similar material combinations.
- Published
- 2021
13. Surface Composition of a Highly Active Pt 3 Y Alloy Catalyst for Application in Low Temperature Fuel Cells
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Björn Eriksson, Ivan Khalakhan, Rosemary Brown, Iva Matolínová, Niklas Lindahl, Vladimír Matolín, Mykhailo Vorokhta, Tomáš Skála, Björn Wickman, and Carina Lagergren
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Materials science ,Renewable Energy, Sustainability and the Environment ,020209 energy ,Sputter cleaning ,Oxide ,Energy Engineering and Power Technology ,chemistry.chemical_element ,Proton exchange membrane fuel cell ,02 engineering and technology ,Yttrium ,021001 nanoscience & nanotechnology ,Electrocatalyst ,Nanomaterial-based catalyst ,Overlayer ,chemistry.chemical_compound ,chemistry ,Chemical engineering ,0202 electrical engineering, electronic engineering, information engineering ,0210 nano-technology ,Platinum - Abstract
Currently, platinum is the most widely used catalyst for low temperature proton exchange membrane fuel cells (PEMFC). However, the kinetics at the cathode are slow, and the price of platinum is high. To improve oxygen reduction reaction (ORR) kinetics at the cathode, platinum can be alloyed with rare earth elements, such as yttrium. We report that Pt3Y has the potential to be over 2 times more active for the ORR compared with Pt inside a real fuel cell. We present detailed photoemission analysis into the nature of the sputtered catalyst surface, using synchrotron radiation photoelectron spectroscopy (SRPES) to examine if surface adsorbates or impurities are present and can be removed. Pretreatment removes most of the yttrium oxide in the surface leaving behind a Pt overlayer which is only a few monolayers thick. Evidence of a substochiometric oxide peak in the Y 3d core level is presented, this oxide extends into the surface even after Ar+ sputter cleaning in-situ. This information will aid the development of new highly active nanocatalysts for employment in real fuel cell electrodes.
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- 2020
14. Oxygen Reduction Reaction Kinetics on a Pt Thin Layer Electrode in Aemfc
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Eva Marra, Henrik Grimler, Gerard Montserrat-Sisó, Rakel Wreland Lindström, Björn Wickman, Göran Lindbergh, and Carina Lagergren
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History ,Polymers and Plastics ,General Chemical Engineering ,Electrochemistry ,Business and International Management ,Industrial and Manufacturing Engineering - Published
- 2022
15. Investigation of 2D Boridene from First Principles and Experiments
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Pernilla Helmer, Joseph Halim, Jie Zhou, Roopathy Mohan, Björn Wickman, Jonas Björk, and Johanna Rosen
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Biomaterials ,Electronic structure ,Boridene ,MBene ,Surface terminations ,Electrochemistry ,Materials Chemistry ,HER ,Materialkemi ,Condensed Matter Physics ,Electronic, Optical and Magnetic Materials - Abstract
Recently, a 2D metal boride - boridene - has been experimentally realized in the form of single-layer molybdenum boride sheets with ordered metal vacancies, through selective etching of the nanolaminated 3D parent borides (Mo2/3Y1/3)2AlB2 and (Mo2/3Sc1/3)2AlB2. The chemical formula of the boridene was suggested to be Mo4/3B2-xTz, where Tz denotes surface terminations. Here, the termination composition and material properties of Mo4/3B2-xTz from both theoretical and experimental perspectives are investigated. Termination sites are considered theoretically for termination species T = O, OH, and F, and the energetically favored termination configuration is identified at z = 2 for both single species terminations and binary termination mixes of different stoichiometries in ordered and disordered configurations. Mo4/3B2-xTz is shown to be dynamically stable for multiple termination stoichiometries, displaying semiconducting, semimetallic, or metallic behavior depending on how different terminations are combined. The approximate chemical formula of a freestanding film of boridene is attained as Mo1.33B1.9O0.3(OH)1.5F0.7 from X-ray photoelectron spectroscopy (XPS) analysis which, within error margins, is consistent with the theoretical results. Finally, metallic and additive-free Mo4/3B2-xTz shows high catalytic performance for the hydrogen evolution reaction, with an onset potential of 0.15 V versus the reversible hydrogen electrode. Funding agencies: The Knut and Alice Wallenberg Foundation (KAW 2020.0033), The Swedish Foundation for Strategic Research (EM16-0004 and ARC19-0026), The Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linköping University (Faculty Grant SFO-Mat-LiU No 2009 00971), The Swedish Research Council (no. 2018-03927 and 2019-04233). The calculations were carried out using supercomputer resources provided by the Swedish National Infrastructure for Computing (SNIC) at the National Supercomputer Centre (NSC) and the PDC Center for high-performance computing partially funded by the Swedish Research Council through grant agreement no. 2018-05973.
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- 2022
16. Unraveling the Surface Chemistry and Structure in Highly Active Sputtered Pt3Y Catalyst Films for the Oxygen Reduction Reaction
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Milan Dopita, Tomáš Skála, Rosemary Brown, Konstantin M. Neyman, Ivan Khalakhan, Thomas Vonderach, Iva Matolínová, Henrik Grönbeck, Niklas Lindahl, Vladimír Matolín, Mykhailo Vorokhta, and Björn Wickman
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Materials science ,Oxide ,chemistry.chemical_element ,Proton exchange membrane fuel cell ,02 engineering and technology ,Yttrium ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Overlayer ,Catalysis ,chemistry.chemical_compound ,chemistry ,X-ray photoelectron spectroscopy ,Chemical engineering ,General Materials Science ,Thin film ,0210 nano-technology ,Platinum - Abstract
Platinum is the most widely used and best performing sole element for catalyzing the oxygen reduction reaction (ORR) in low-temperature fuel cells. Although recyclable, there is a need to reduce the amount used in current fuel cells for their extensive uptake in society. Alloying platinum with rare-earth elements such as yttrium can provide an increase in activity of more than seven times, reducing the amount of platinum and the total amount of catalyst material required for the ORR. As yttrium is easily oxidized, exposure of the Pt-Y catalyst layer to air causes the formation of an oxide layer that can be removed during acid treatment, leaving behind a highly active pure platinum overlayer. This paper presents an investigation of the overlayer composition and quality of Pt3Y films sputtered from an alloy target. The Pt3Y catalyst surface is investigated using synchrotron radiation X-ray photoelectron spectroscopy before and after acid treatment. A new substoichiometric oxide component is identified. The oxide layer extends into the alloy surface, and although it is not completely removed with acid treatment, the catalyst still achieves the expected high ORR activity. Other surface-sensitive techniques show that the sputtered films are smooth and bulk X-ray diffraction reveals many defects and high microstrain. Nevertheless, sputtered Pt3Y exhibits a very high activity regardless of the film's oxide content and imperfections, highlighting Pt3Y as a promising catalyst. The obtained results will help to support its integration into fuel cell systems.
- Published
- 2019
17. Decontamination of Mercury-Containing Aqueous Streams by Electrochemical Alloy Formation on Copper
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Mattias K. O. Bengtsson, Cristian Tunsu, and Björn Wickman
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Aqueous solution ,General Chemical Engineering ,Inorganic chemistry ,chemistry.chemical_element ,Sulfuric acid ,02 engineering and technology ,General Chemistry ,Human decontamination ,021001 nanoscience & nanotechnology ,Electrochemistry ,Copper ,Industrial and Manufacturing Engineering ,Mercury (element) ,chemistry.chemical_compound ,020401 chemical engineering ,chemistry ,0204 chemical engineering ,0210 nano-technology ,Platinum ,Dissolution - Abstract
Mercury in aqueous streams poses severe health and environmental concerns and requires improved techniques for decontamination. One such technique is electrochemical alloy formation on platinum, which can effectively decontaminate mercury-containing aqueous streams at concentrations relevant for both industrial and natural waters. This study examines the viability of copper as an alternative to platinum. Mercury removal is faster on copper and works both with and without an applied cathodic potential. Without it, however, copper dissolution becomes a problem. Copper dissolution is preventable in neutral pH and in sulfuric acid solutions under potential control, and dissolved copper ions can be plated back onto the electrode. In the presence of nitrate or chloride anions, copper electrodes degrade rapidly even under potential control. Thus, there are practical restrictions for mercury decontamination via electrochemical alloy formation on copper, but it can be applied to solutions where copper is stable under potential control.
- Published
- 2019
18. Tunning the Activity of Silver Alloy Electrocatalysts for the Oxygen Reduction Reaction in Alkaline Media
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Gerard Montserrat Siso and Björn Wickman
- Abstract
A bottleneck to achieve efficient and stable electrocatalysts for Anion Exchange Membrane Fuel Cells (AEMFCs) is the relatively slow kinetics of the oxygen reduction reaction (ORR) taking place at the cathode. The rather mild alkaline conditions in the AEMFC enable the utilization of various PGM-free catalysts, which brings up new possibilities of finding abundant and inexpensive electrocatalysts without compromising the power density. From theory and previous experiments, it is known that Au and Ag bind oxygen weakly, whereas other transition metals (e.g., Pd, Cu, Fe, Ni) bind strongly to oxygenated species1. Therefore, a suitable geometric arrangement between Ag, an abundant metal with relatively high specific activity, and other metals may give rise to optimum binding of oxygen and thus a high activity. A good strategy to improve the activity of Ag-based catalysts could be a rational design of alloys that can enhance the intrinsic activity of Ag by both ensemble and electronic effects2–4. The former is based on the combination of active sites that facilitate the initial oxygen binding together with Ag active sites that help desorb hydroxide anions, whereas the latter is induced by the alloying metal (which binds oxygenated species strongly) on the electronic structure of the overlaying Ag that tunes its binding to oxygen5. Herein, we report the fabrication and characterization of Ag thin-films alloyed with Pd, Ni, Cu and Mo as a tool to investigate the ORR reaction in terms of ensemble and electronic effects and thus relate alloy composition and geometric arrangement with ORR activity. Ag thin-film model catalysts are fabricated by means of physical vapor deposition methods (PVD) with high control over the amount of material deposited. By varying alloy composition and evaluating electrochemical activity and stability, together with detailed physical characterization, the degree and extent of electronic effects are elucidated. In the same way, sputtering of the same amount of Ag on thin-films of different metals evidences the role of the alloying metal on tuning the activity of Ag through an adjustment of its d-band that changes the binding of oxygenated species, as well as through an ensemble effect that provides active sites for the first elementary steps of the reaction. These results provide insights for more tailored design of electrocatalysts in alkaline media by shedding new light on the mechanisms through which the ORR kinetics are improved in alkaline media. Nørskov, J. K. et al. Origin of the overpotential for oxygen reduction at a fuel-cell cathode. J. Phys. Chem. B 108, 17886–17892 (2004). Betancourt, L. E. et al. Enhancing ORR Performance of Bimetallic PdAg Electrocatalysts by Designing Interactions between Pd and Ag. ACS Appl. Energy Mater. 3, 2342–2349 (2020). Slanac, D. A., Hardin, W. G., Johnston, K. P. & Stevenson, K. J. Atomic ensemble and electronic effects in Ag-rich AgPd nanoalloy catalysts for oxygen reduction in alkaline media. J. Am. Chem. Soc. 134, 9812–9819 (2012). Zamora Zeledón, J. A. et al. Tuning the electronic structure of Ag-Pd alloys to enhance performance for alkaline oxygen reduction. Nat. Commun. 12, 1–9 (2021). Stamenkovic, V. et al. Changing the Activity of Electrocatalysts for Oxygen Reduction by Tuning the Surface Electronic Structure. Angew. Chemie 118, 2963–2967 (2006).
- Published
- 2022
19. Platinum-Based Nanoparticle Fuel Cell Catalysts Synthesized By Sputtering Onto Liquid Substrates
- Author
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Björn Lönn, Rosemary Brown, Robin Pfeiffer, Henrik Frederiksen, and Björn Wickman
- Abstract
The quest of finding cheaper and better fuel cell catalyst materials has been long ongoing and remains a crucial step in making fuel cells a commercially viable technology. Platinum (Pt) is still the conventional catalyst used in proton exchange membrane (PEM) fuel cells, however, with slow cathode kinetics and high material cost. Platinum-rare earth (RE) and lanthanide alloys have been found to greatly enhance the catalytic activity towards the oxygen reduction reaction (ORR).1 Increases in ORR activity of up to one order of magnitude compared to pure platinum has been observed for these alloys, but high oxygen affinity of the RE alloying agents considerably complicates their synthesis. Sputter deposition into low vapor pressure liquid substrates, such as ionic liquids and certain polymers enables fabrication of clean nanoparticles, without the presence of air and other contaminates, making it a potential technique for Pt-RE nanoparticle synthesis. Here, we will present our recent work on magnetron sputtering of Pt 2 and Pt-alloys into different liquid substrates, including polyethylene glycol and three imidazolium-based ionic liquids. We have investigated the influence of substrate temperature on Pt nanoparticle growth during sputtering, and in post-sputtering heat treatment.2 We show that whilst substrate temperature influences the Pt nanoparticle size, the effect is not as great as for other materials. Better understanding the growth processes of Pt nanoparticles sputtered into liquids is an important step towards tunable sizes and catalytic activities of Pt-RE nanocatalysts. Escudero-Escribano, María, et al. "Tuning the activity of Pt alloy electrocatalysts by means of the lanthanide contraction." Science 352.6281 (2016): 73-76. Brown, Rosemary, et al. "Plasma-Induced Heating Effects on Platinum Nanoparticle Size During Sputter Deposition Synthesis in Polymer and Ionic Liquid Substrates." Langmuir 37.29 (2021): 8821-8828.
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- 2022
20. PdNi thin films for hydrogen oxidation reaction and oxygen reduction reaction in alkaline media
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Gerard Montserrat-Sisó and Björn Wickman
- Subjects
General Chemical Engineering ,Electrochemistry - Published
- 2022
21. Effective removal of mercury from aqueous streams via electrochemical alloy formation on platinum
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Björn Wickman and Cristian Tunsu
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Materials science ,Metal ions in aqueous solution ,Science ,Inorganic chemistry ,Alloy ,General Physics and Astronomy ,chemistry.chemical_element ,02 engineering and technology ,010501 environmental sciences ,engineering.material ,Electrochemistry ,01 natural sciences ,General Biochemistry, Genetics and Molecular Biology ,Article ,law.invention ,law ,lcsh:Science ,0105 earth and related environmental sciences ,Multidisciplinary ,Aqueous solution ,General Chemistry ,Human decontamination ,021001 nanoscience & nanotechnology ,Cathode ,Mercury (element) ,chemistry ,engineering ,lcsh:Q ,0210 nano-technology ,Platinum - Abstract
Retrieval of mercury from aqueous streams has significant environmental and societal importance due to its very high toxicity and mobility. We present here a method to retrieve mercury from aqueous feeds via electrochemical alloy formation on thin platinum films. This application is a green and effective alternative to traditional chemical decontamination techniques. Under applied potential, mercury ions in solution form a stable PtHg4 alloy with platinum on the cathode. A 100 nanometres platinum film was fully converted to a 750 nanometres thick layer of PtHg4. The overall removal capacity is very high, > 88 g mercury per cm3. The electrodes can easily be regenerated after use. Efficient and selective decontamination is possible in a wide pH range, allowing processing of industrial, municipal, and natural waters. The method is suited for both high and low concentrations of mercury and can reduce mercury levels far below the limits allowed in drinking water., Removal of anthropogenic mercury from water streams is of great importance given its high toxicity and ability to spread rapidly. Here, the authors demonstrate the direct alloying of mercury with a fully recyclable platinum electrode, providing effective removal at different concentrations and pH, and in the presence of other contaminants.
- Published
- 2018
22. Hydrogen induced interface engineering in Fe
- Author
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Aadesh P, Singh, Richard Baochang, Wang, Camilla, Tossi, Ilkka, Tittonen, Björn, Wickman, and Anders, Hellman
- Abstract
Semiconductor heterostructure junctions are known to improve the water oxidation performance in photoelectrochemical (PEC) cells. Depending on the semiconductor materials involved, different kinds of junctions can appear, for instance, type II band alignment where the conduction and valence bands of the semiconductor materials are staggered with respect to each other. This band alignment allows for a charge separation of the photogenerated electron-hole pairs, where the holes will go from low-to-high valance band levels and
- Published
- 2020
23. Synergies of co-doping in ultra-thin hematite photoanodes for solar water oxidation: In and Ti as representative case
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Aadesh P. Singh, Camilla Tossi, Ilkka Tittonen, Anders Hellman, Björn Wickman, Department of Neuroscience and Biomedical Engineering, Department of Electronics and Nanoengineering, Chalmers University of Technology, Aalto-yliopisto, and Aalto University
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Photocurrent ,Materials science ,Dopant ,General Chemical Engineering ,Doping ,chemistry.chemical_element ,02 engineering and technology ,General Chemistry ,Substrate (electronics) ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,7. Clean energy ,Evaporation (deposition) ,0104 chemical sciences ,chemistry ,Chemical engineering ,Water splitting ,Thin film ,0210 nano-technology ,Indium - Abstract
Solar energy induced water splitting in photoelectrochemical (PEC) cells is one of the most sustainable ways of hydrogen production. The challenge is to develop corrosion resistant and chemically stable semiconductors that absorb sunlight in the visible region and, at the same time, have the band edges matching with the redox level of water. In this work, hematite (α-Fe2O3) thin films were prepared onto an indium-doped tin oxide (ITO; In:SnO2) substrate by e-beam evaporation of Fe, followed by air annealing at two different temperatures: 350 and 500 °C. The samples annealed at 500 °C show an in situ diffusion of indium from the ITO substrate to the surface of α-Fe2O3, where it acts as a dopant and enhances the photoelectrochemical properties of hematite. Structural, optical, chemical and photoelectrochemical analysis reveal that the diffusion of In at 500 °C enhances the optical absorption, increases the electrode–electrolyte contact area by changing the surface topology, improves the carrier concentration and shifts the flat band potential in the cathodic direction. Further enhancement in photocurrent density was observed by ex situ diffusion of Ti, deposited in the form of nanodisks, from the top surface to the bulk. The in situ In diffused α-Fe2O3 photoanode exhibits an improved photoelectrochemical performance, with a photocurrent density of 145 μA cm−2 at 1.23 VRHE, compared to 37 μA cm−2 for the photoanode prepared at 350 °C; it also decreases the photocurrent onset potential from 1.13 V to 1.09 V. However, the In/Ti co-doped sample exhibits an even higher photocurrent density of 290 μA cm−2 at 1.23 VRHE and the photocurrent onset potential decreases to 0.93 VRHE, which is attributed to the additional doping and to the surface becoming more favorable to charge separation.
- Published
- 2020
24. Extended visible light harvesting and boosted charge carrier dynamics in heterostructured zirconate–FeS2 photocatalysts for efficient solar water splitting
- Author
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J.M. Mora-Hernández, Leticia M. Torres-Martínez, D. Sánchez-Martínez, Björn Wickman, María E. Zarazúa-Morín, Edgar Moctezuma, and Ali M. Huerta-Flores
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Materials science ,business.industry ,Heterojunction ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,Effective nuclear charge ,0104 chemical sciences ,Electronic, Optical and Magnetic Materials ,Photocatalysis ,Water splitting ,Optoelectronics ,Charge carrier ,Electrical and Electronic Engineering ,0210 nano-technology ,business ,Absorption (electromagnetic radiation) ,Photocatalytic water splitting ,Visible spectrum - Abstract
Limited visible light absorption, slow charge transference, and high recombination are some of the main problems associated with low efficiency in photocatalytic processes. For these reasons, in the present work, we develope novel zirconate–FeS2 heterostructured photocatalysts with improved visible light harvesting, effective charge separation and high photocatalytic water splitting performance. Herein, alkali and alkaline earth metal zirconates are prepared by a solid state reaction and coupled to FeS2 through a simple wet impregnation method. The incorporation of FeS2 particles induces visible light absorption and electron injection in zirconates, while the appropriate coupling of the semiconductors in the heterostructure allows an enhanced charge separation and suppression of the recombination. The obtained heterostructures exhibit high and stable photocatalytic activity for water splitting under visible light, showing competitive efficiencies among other reported materials. The highest hydrogen evolution rate (4490 µmol g−1 h−1) is shown for BaZrO3–FeS2 and corresponds to more than 20 times the activity of the bare BaZrO3. In summary, this work proposes novel visible light active heterostructures for efficient visible light photocatalytic water splitting.
- Published
- 2018
25. Synthesis of MoS2-TiO2 nanocomposite for enhanced photocatalytic and photoelectrochemical performance under visible light irradiation
- Author
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Manan Mehta, Sandeeep Kumar, Aadesh P. Singh, Suddhasatwa Basu, Björn Wickman, and Satheesh Krishnamurthy
- Subjects
Nanocomposite ,Materials science ,Scanning electron microscope ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,0104 chemical sciences ,Surfaces, Coatings and Films ,chemistry.chemical_compound ,symbols.namesake ,Chemical engineering ,chemistry ,X-ray photoelectron spectroscopy ,Transmission electron microscopy ,Rhodamine B ,symbols ,Photocatalysis ,Hydrothermal synthesis ,0210 nano-technology ,Raman spectroscopy ,Instrumentation - Abstract
In this work, we have prepared MoS2 nanoflakes modified TiO2 nanoparticles (MoS2-TiO2 nanocomposite) with varying concentration of MoS2 (2.5–10 wt.%) by a two-step hydrothermal synthesis method involving specific preparation conditions for the TiO2 nanoparticles and MoS2 nanoflakes. The prepared samples were characterized by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray analysis (EDX), and X-ray photoelectron spectroscopy (XPS) techniques. The photocatalytic activity of the pristine TiO2 nanoparticles and MoS2-TiO2 nanocomposite samples were evaluated by examining the photocatalytic degradation of Rhodamine B (RhB). The photoelectrochemical activity of these samples were measured by performing solar water splitting experiments under visible light irradiation. It was observed that the MoS2-TiO2 nanocomposite with 7.5 wt.% MoS2 exhibits highest photocatalytic and photoelectrochemical activity as it has the optimum amount of MoS2 nanoflakes which probably minimizes the recombination of photogenerated charge carriers as compared to other concentrations of MoS2 in MoS2-TiO2 nanocomposite and pristine TiO2 nanoparticles. In addition, a rather high photocatalytic reaction rate constant was observed for MoS2-TiO2 nanocomposite with 7.5 wt.% MoS2 nanoflakes.
- Published
- 2018
26. Unraveling the Surface Chemistry and Structure in Highly Active Sputtered Pt
- Author
-
Rosemary, Brown, Mykhailo, Vorokhta, Ivan, Khalakhan, Milan, Dopita, Thomas, Vonderach, Tomáš, Skála, Niklas, Lindahl, Iva, Matolínová, Henrik, Grönbeck, Konstantin M, Neyman, Vladimír, Matolín, and Björn, Wickman
- Abstract
Platinum is the most widely used and best performing sole element for catalyzing the oxygen reduction reaction (ORR) in low-temperature fuel cells. Although recyclable, there is a need to reduce the amount used in current fuel cells for their extensive uptake in society. Alloying platinum with rare-earth elements such as yttrium can provide an increase in activity of more than seven times, reducing the amount of platinum and the total amount of catalyst material required for the ORR. As yttrium is easily oxidized, exposure of the Pt-Y catalyst layer to air causes the formation of an oxide layer that can be removed during acid treatment, leaving behind a highly active pure platinum overlayer. This paper presents an investigation of the overlayer composition and quality of Pt
- Published
- 2019
27. Green synthesis of earth-abundant metal sulfides (FeS2, CuS, and NiS2) and their use as visible-light active photocatalysts for H2 generation and dye removal
- Author
-
Björn Wickman, Ali M. Huerta-Flores, Aadesh P. Singh, Leticia M. Torres-Martínez, and Edgar Moctezuma
- Subjects
Materials science ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Electrochemistry ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,Hydrothermal circulation ,0104 chemical sciences ,Electronic, Optical and Magnetic Materials ,Metal ,chemistry.chemical_compound ,Indigo carmine ,chemistry ,Chemical engineering ,Reagent ,visual_art ,visual_art.visual_art_medium ,Photocatalysis ,Crystallite ,Electrical and Electronic Engineering ,0210 nano-technology ,Visible spectrum - Abstract
Earth-abundant metal sulfides (for example, FeS2, CuS, and NiS2) are promising materials to be used as photocatalysts due to their suitable electronic and optical properties. In this work, we present a fast and low-cost hydrothermal method to synthesize these materials. They are integrally characterized and evaluated as photocatalysts for the H2 evolution reaction and the degradation of indigo carmine (IC). FeS2 exhibits the highest photocatalytic efficiency (32 µmol g−1 h−1 of H2 evolution and 88% of indigo carmine degradation) under visible light, and this activity is attributed to a larger crystallite size, smaller particle size, and lower recombination, compared to CuS and NiS2. Moreover, three different sacrificial reagents are studied for the H2 evolution reaction, including Na2S/Na2SO3, EDTA, and ethanol. Na2S/Na2SO3 shows the highest enhancement in the activity, increasing the rate of H2 production more than 15 times. This behavior is related to the lower oxidation potential of Na2S/Na2SO3. Moreover, we evaluate the activity of the materials for the electrochemical hydrogen evolution reaction (HER). In summary, this work provides valuable information for effective applications of these earth-abundant metal sulfides for energy and environmental photocatalytic processes.
- Published
- 2018
28. Electrooxidation of Glycerol on Gold in Acidic Medium: A Combined Experimental and DFT Study
- Author
-
Anders Hellman, Jonas Baltrusaitis, Henrik Grönbeck, Björn Wickman, Michael Busch, and Mikael Valter
- Subjects
Inorganic chemistry ,Dihydroxyacetone ,02 engineering and technology ,Pourbaix diagram ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,chemistry.chemical_compound ,General Energy ,chemistry ,Glyceraldehyde ,Glycerol ,Reversible hydrogen electrode ,Dehydrogenation ,Physical and Theoretical Chemistry ,Cyclic voltammetry ,0210 nano-technology ,Carbon monoxide - Abstract
Glycerol is a byproduct of biodiesel production and an abundant feedstock for the synthesis of high-value chemicals. A promising approach for valorization of glycerol is electrooxidation on gold. In this work, we investigate electrooxidation of glycerol on gold in acidic media using cyclic voltammetry and density functional theory calculations. Experimentally, we observe activity for electrooxidation above a potential of 0.5 V versus the reversible hydrogen electrode (RHE). A Pourbaix diagram is calculated to evaluate the surface coverage under reaction conditions, indicating that the surface is free from adsorbates at the measured onset potential. Computationally, we find that the onset potentials for partial dehydrogenation of glycerol to dihydroxyacetone, 2,3-dihydroxy-2-propenal, and glyceraldehyde are 0.39, 0.39, and 0.60 V versus RHE, respectively, while complete dehydrogenation to carbon monoxide requires 0.50 V versus RHE. Our theoretical and experimental findings are in agreement and show the pos...
- Published
- 2018
29. Fuel Cell Measurements with Cathode Catalysts of Sputtered Pt3 Y Thin Films
- Author
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Rakel Wreland Lindström, Göran Lindbergh, Björn Wickman, Björn Eriksson, Carina Lagergren, Henrik Grönbeck, and Niklas Lindahl
- Subjects
Materials science ,General Chemical Engineering ,Alloy ,Proton exchange membrane fuel cell ,chemistry.chemical_element ,02 engineering and technology ,engineering.material ,010402 general chemistry ,01 natural sciences ,Catalysis ,law.invention ,law ,Environmental Chemistry ,General Materials Science ,Thin film ,Porosity ,technology, industry, and agriculture ,Yttrium ,equipment and supplies ,021001 nanoscience & nanotechnology ,Cathode ,0104 chemical sciences ,General Energy ,Chemical engineering ,chemistry ,engineering ,0210 nano-technology ,Platinum - Abstract
Fuel cells are foreseen to have an important role in sustainable energy systems, provided that catalysts with higher activity and stability are developed. In this study, highly active sputtered thin films of platinum alloyed with yttrium (Pt 3 Y) are deposited on commercial gas diffusion layers and their performance in a proton exchange membrane fuel cell is measured. After acid pretreatment, the alloy is found to have up to 2.5 times higher specific activity than pure platinum. The performance of Pt 3 Y is much higher than that of pure Pt, even if all of the alloying element was leached out from parts of the thin metal film on the porous support. This indicates that an even higher performance is expected if the structure of the Pt 3 Y catalyst or the support could be further improved. The results show that platinum alloyed with rare earth metals can be used as highly active cathode catalyst materials, and significantly reduce the amount of platinum needed, in real fuel cells.
- Published
- 2018
30. Enhanced oxygen reduction activity with rare earth metal alloy catalysts in proton exchange membrane fuel cells
- Author
-
Rakel Wreland Lindström, Tomáš Skála, Björn Wickman, Gerard Montserrat-Sisó, Carina Lagergren, Rosemary Brown, Björn Eriksson, and Göran Lindbergh
- Subjects
Materials science ,General Chemical Engineering ,Alloy ,Proton exchange membrane fuel cell ,chemistry.chemical_element ,02 engineering and technology ,Sputter deposition ,engineering.material ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Cathode ,0104 chemical sciences ,law.invention ,Catalysis ,Overlayer ,chemistry ,X-ray photoelectron spectroscopy ,Chemical engineering ,law ,Electrochemistry ,engineering ,0210 nano-technology ,Platinum - Abstract
Alloying platinum is an approach to increase the oxygen reduction reaction (ORR) activity and at the same time reduce the amount of precious platinum catalyst in proton exchange membrane fuel cells (PEMFC). In this work the cathode activity of thin films of rare earth metals (REM) alloys, Pt3Y, Pt5Gd and Pt5Tb, produced by sputter deposition onto gas diffusion layers, are evaluated in a fuel cell by means of polarization curves in O2/H2, and cyclic- and CO-stripping voltammetry in N2/5% H2. Prior to evaluation, the model electrodes were acid-treated to obtain a Pt skin covering the PtREM alloy bulk, as was revealed by energy-dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS). The core shell alloys of Pt3Y and Pt5Gd catalysts show a specific activity enhancement at 0.9 V of 2.5 times compared to pure Pt. The slightly lower enhancement factor of 2.0 for Pt5Tb is concluded to be due to leaching of the REM, that resulted in a thicker, and subsequently less strained, Pt overlayer. The high activity, combined with the minor changes in surface composition, achieved in the fuel cell environment shows that PtREM core shell catalysts are promising for the cathode reaction in PEMFC.
- Published
- 2021
31. The effect of O2 concentration on the reaction mechanism in Li-O2 batteries
- Author
-
Ann Cornell, Björn Wickman, Mårten Behm, Jonas Lindberg, and Göran Lindbergh
- Subjects
Battery (electricity) ,Reaction mechanism ,Chemistry ,General Chemical Engineering ,Inorganic chemistry ,Analytical chemistry ,02 engineering and technology ,Quartz crystal microbalance ,Electrolyte ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Electrochemistry ,01 natural sciences ,0104 chemical sciences ,Analytical Chemistry ,Electrode ,0210 nano-technology ,Saturation (chemistry) ,Faraday efficiency - Abstract
The promising lithium-oxygen battery chemistry presents a set of challenges that need to be solved if commercialization is ever to be realized. This study focuses on how the O2 reaction path is effected by the O2 concentration in the electrolyte. An electrochemical quartz crystal microbalance system was used to measure current, potential, and change in electrode mass simultaneously. It is concluded that the mass reversibility is O2 concentration dependent while the coulombic efficiency is not. The mass reversibility is higher at low O2 concentration meaning that more of the deposited Li2O2 is removed during oxidation in relation to the amount deposited during reduction. The first step of the reduction is the formation of soluble LiO2, which is then either reacting further at the electrode or being transported away from the electrode resulting in low current efficiency and low deposited mass per electrons transferred. During the oxidation, the first step involves de-lithiation of Li2O2 at low potential followed by bulk oxidation. The oxidation behavior is O2 concentration dependent, and this dependence is likely indirect as the O2 concentration effects the amount of discharge product formed during the reduction. The O2 concentration at different saturation pressures was determined using a mass spectrometer. It was found that the electrolyte follows Henry's law at the pressures used in the study. In conclusion, this study provides insight to the O2 concentration dependence and the preferred path of the O2 electrochemical reactions in lithium-oxygen batteries.
- Published
- 2017
32. Dominant {100} facet selectivity for enhanced photocatalytic activity of NaNbO3in NaNbO3/CdS core/shell heterostructures
- Author
-
Meganathan Thirumal, Ashok K. Ganguli, Sandeep Kumar, Aadesh P. Singh, R. Parthasarathy, and Björn Wickman
- Subjects
Materials science ,Heterojunction ,Nanotechnology ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Catalysis ,Surface energy ,0104 chemical sciences ,Crystal ,Chemical engineering ,Phase (matter) ,Photocatalysis ,Water splitting ,Orthorhombic crystal system ,Facet ,0210 nano-technology - Abstract
Design and engineering of crystalline advanced photocatalysts with specific facets is one of the most challenging tasks to enhance the photocatalytic performance. The surface energy of different facets is different in a crystal which leads to a corresponding change in their photocatalytic behaviour. The present study provides an experimental as well as theoretical understanding of the role of different facets of NaNbO3 in cubic and orthorhombic phases with crystals showing cubic and cuboctahedron morphologies in enhancing the photocatalytic activity of NaNbO3/CdS core/shell heterostructures. Herein, we discuss the importance of the approach of facet-selective synthesis and trace the origin of enhanced photoelectrochemical (PEC) water splitting and photocatalytic dye degradation activity for calculated surface energies of the {100} family of facets of the cubic phase and the (110) and (114) facets of the orthorhombic phase of NaNbO3. We propose that different mechanisms contribute to the enhancement of catalytic activity in these two phases. In the prepared core/shell heterostructures containing NaNbO3 as the core material, the presence of highly reactive facets of the cubic phase contributes to higher photocatalytic activity as compared to the orthorhombic phase which has a spatial charge separation assisted inter-facet charge transfer mechanism.
- Published
- 2017
33. Hydrogen Treatment and FeOOH overlayer: Effective approaches for enhancing the photoelectrochemical water oxidation performance of bismuth vanadate thin films
- Author
-
Anders Hellman, Björn Wickman, Beniamino Iandolo, Aadesh P. Singh, Nishant Saini, and Bodh Raj Mehta
- Subjects
Hydrogen treatment ,Materials science ,Hydrogen ,chemistry.chemical_element ,02 engineering and technology ,Electrolyte ,010402 general chemistry ,01 natural sciences ,Catalysis ,Overlayer ,chemistry.chemical_compound ,Solar hydrogen ,Thin film ,Photoelectrochemical ,Photocurrent ,business.industry ,General Chemistry ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,Dielectric spectroscopy ,Semiconductor ,chemistry ,Chemical engineering ,Bismuth vanadate ,FeOOH ,0210 nano-technology ,business - Abstract
The water oxidation capability of the promising photoanode bismuth vanadate (BiVO4) is hampered by poor bulk electron transport and by high rates of charge recombination at the semiconductor/electrolyte interface. Here, we demonstrate that a dual modification of BiVO4 by: (i) annealing in a hydrogen-containing environment and (ii) coating with FeOOH overlayer substantially enhances the water oxidation ability of BiVO4 photoanodes. Hydrogen treated, FeOOH coated BiVO4 photoanodes exhibit a water oxidation photocurrent density of 2.16 mA cm−2 at 1.23 VRHE, which is 5 times higher than for untreated BiVO4 films. Moreover, they showed an impressive low photocurrent onset potential of −0.11 VRHE. A stable photocurrent was observed for 1 h of water oxidation measurement at 1.23 VRHE under 1 Sun illumination. The enhanced photocurrent of FeOOH/H:BiVO4 photoanode is ascribed to an improved bulk charge transport, as confirmed by impedance spectroscopy measurements and Mott-Schottky analysis. The cathodic shift of the onset potential originates from a lowering of the flat band potential and from an improvement of the charge transport at the semiconductor/electrolyte interface. The dual modification strategy used here offers a simple but effective approach of improving the water oxidation performance of BiVO4.
- Published
- 2019
34. Efficient separation of precious metals from computer waste printed circuit boards by hydrocyclone and dilution-gravity methods
- Author
-
Mohammad Reza Bilesan, Björn Wickman, Eveliina Repo, and I. V. Makarova
- Subjects
Green chemistry ,Hydrocyclone ,Materials science ,Renewable Energy, Sustainability and the Environment ,Scanning electron microscope ,business.industry ,020209 energy ,Strategy and Management ,05 social sciences ,Fraction (chemistry) ,02 engineering and technology ,Industrial and Manufacturing Engineering ,law.invention ,Grinding ,Printed circuit board ,law ,050501 criminology ,0202 electrical engineering, electronic engineering, information engineering ,Atomic absorption spectroscopy ,Process engineering ,business ,Spectroscopy ,0505 law ,General Environmental Science - Abstract
To fulfill the different aspects of green chemistry and to achieve full use of the secondary resources (waste printed circuit boards (WPCB)), the necessity of developing green methods for recovery of precious metals (Au, Pd, and Ag) is highly demanded. In this study, a novel environment-friendly physical separation approach; the combination of crushing, grinding, sieving as pretreatment steps alongside hydrocyclone and the dilution-gravity method (DGM) as the main final steps; is proposed. Inductively coupled plasma-mass spectrometry (ICP-MS), atomic absorption spectroscopy (AAS), and energy-dispersive X-ray spectroscopy (EDS) characterization methods were utilized to understand the effects of different separation steps applied in this research. The size and shape of grinded materials and the ones produced after hydrocyclone and DGM were evaluated using scanning electron microscopy. The results showed that the sieving step separated the highest gold fraction in the finer classification (
- Published
- 2021
35. Improved water oxidation performance of ultra-thin planar hematite photoanode: Synergistic effect of In/Sn doping and an overlayer of metal oxyhydroxides
- Author
-
Jani Oksanen, Beniamino Iandolo, Björn Wickman, Alexander Levinsson, Anders Hellman, and Aadesh P. Singh
- Subjects
Photocurrent ,Thin layers ,Chemistry ,General Chemical Engineering ,Doping ,General Physics and Astronomy ,chemistry.chemical_element ,02 engineering and technology ,General Chemistry ,Substrate (electronics) ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Amorphous solid ,Overlayer ,Chemical engineering ,0210 nano-technology ,Tin ,Indium - Abstract
Hematite is a promising photoanode candidate with many favorable material properties, such as stability and suitable band-gap. However, there are some severe challenges, including high losses due to charge recombination and slow oxidation kinetics, which can be addressed by doping and addition of co-catalysts. Here, the effects of temperature driven diffusion of substrate impurities (doping) and subsequent surface modification by metal oxy-hydroxides (co-catalysts) have been studied for enhanced water-oxidation performance in photoelectrochemical (PEC) measurements. Diffusion of indium and tin from the indium-doped tin oxide (ITO) substrate into planar films of α-Fe2O3 photoanodes results in a photocurrent density (Jph) of 0.09 mA/cm2, corresponding to an approximate 9-fold enhancement over the control pristine α-Fe2O3 (0.01 mA/cm2) at 1.23 VRHE. A thin amorphous FeOOH coating over the In/Sn co-doped α-Fe2O3 photoanode improves the water oxidation performance further, with a 211 % enhancement in Jph at 1.23 VRHE and a 0.21 V cathodic shift in onset potential. Thin layers of NiOOH and FeNiOOH co-catalysts exhibit 100 and 155 % enhancement in Jph, respectively. Characterization and electrochemical measurements reveal that the enhanced performance is a result of reduced bulk recombination by temperature driven In/Sn substrate impurity doping and improved surface oxidation kinetics by the metal oxy-hydroxide overlayer. Especially deposition of FeOOH onto In/Sn co-doped α-Fe2O3 significantly reduces resistance at the semiconductor/electrolyte interface, leading to the shift in onset potential. Further, the results indicate that all the samples exhibit a quantitative correlation between the cathodic shift in photocurrent onset potential (Vonset) and flat band potential (Vfb).
- Published
- 2020
36. High quality three-dimensional aluminum microwave cavities
- Author
-
David Niepce, Per Delsing, Björn Wickman, J. Biznárová, Marina Kudra, Jonathan Burnett, Simone Gasparinetti, and A. Fadavi Roudsari
- Subjects
010302 applied physics ,Superconductivity ,Materials science ,Photon ,Physics and Astronomy (miscellaneous) ,business.industry ,Annealing (metallurgy) ,chemistry.chemical_element ,Polishing ,02 engineering and technology ,Creative commons ,021001 nanoscience & nanotechnology ,01 natural sciences ,Internal quality ,chemistry ,Aluminium ,0103 physical sciences ,Optoelectronics ,0210 nano-technology ,business ,Microwave - Abstract
We present a comprehensive study of internal quality factors in superconducting stub-geometry three-dimensional cavities made of aluminum. We use wet etching, annealing, and electrochemical polishing to improve the as machined quality factor. We find that the dominant loss channel is split between the two-level system loss and an unknown source with a 40:60 proportion. A total of 17 cavities of different purity, resonance frequency, and size were studied. Our treatment results in reproducible cavities, with 10 of them showing internal quality factors above 80 x 10(6) at a power corresponding to an average of a single photon in the cavity. The best cavity has an internal quality factor of 115 x 10(6) at a single photon level. (C) 2020 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http:// creativecommons.org/licenses/by/4.0/).
- Published
- 2020
37. Fuel Cell Measurements with Cathode Catalysts of Sputtered Pt
- Author
-
Niklas, Lindahl, Björn, Eriksson, Henrik, Grönbeck, Rakel Wreland, Lindström, Göran, Lindbergh, Carina, Lagergren, and Björn, Wickman
- Abstract
Fuel cells are foreseen to have an important role in sustainable energy systems, provided that catalysts with higher activity and stability are developed. In this study, highly active sputtered thin films of platinum alloyed with yttrium (Pt
- Published
- 2018
38. W-Based Atomic Laminates and Their 2D Derivative W
- Author
-
Rahele, Meshkian, Martin, Dahlqvist, Jun, Lu, Björn, Wickman, Joseph, Halim, Jimmy, Thörnberg, Quanzheng, Tao, Shixuan, Li, Saad, Intikhab, Joshua, Snyder, Michel W, Barsoum, Melike, Yildizhan, Justinas, Palisaitis, Lars, Hultman, Per O Å, Persson, and Johanna, Rosen
- Abstract
Structural design on the atomic level can provide novel chemistries of hybrid MAX phases and their MXenes. Herein, density functional theory is used to predict phase stability of quaternary i-MAX phases with in-plane chemical order and a general chemistry (W
- Published
- 2017
39. Electro-oxidation of water on hematite: Effects of surface termination and oxygen vacancies investigated by first-principles
- Author
-
Björn Wickman, Anders Hellman, Beniamino Iandolo, Jonas Baltrusaitis, and Henrik Grönbeck
- Subjects
Electrolysis ,Electrolysis of water ,Inorganic chemistry ,Oxygen evolution ,Oxide ,chemistry.chemical_element ,Surfaces and Interfaces ,Hematite ,Condensed Matter Physics ,Electrochemistry ,Oxygen ,Surfaces, Coatings and Films ,law.invention ,chemistry.chemical_compound ,chemistry ,law ,visual_art ,Materials Chemistry ,visual_art.visual_art_medium ,Reversible hydrogen electrode - Abstract
The oxygen evolution reaction on hydroxyl- and oxygen-terminated hematite was investigated using first-principle calculations within a theoretical electrochemical framework. Both pristine hematite and hematite containing oxygen vacancies were considered. The onset potential was determined to be 1.79 V and 2.09 V vs. the reversible hydrogen electrode (RHE) for the pristine hydroxyl- and oxygen-terminated hematite, respectively. The presence of oxygen vacancies in the hematite surface resulted in pronounced shifts of the onset potential to 3.09 V and 1.83 V. respectively. Electrochemical oxidation measurements conducted on thin-film hematite anodes, resulted in a measured onset potential of 1.66 V vs. RHE. Furthermore, the threshold potential between the hydroxyl- and oxygen-terminated hematite was determined as a function of pH. The results indicate that electrochemical water oxidation on hematite occurs on the oxygen-terminated hematite, containing oxygen vacancies.
- Published
- 2015
40. Correlating flat band and onset potentials for solar water splitting on model hematite photoanodes
- Author
-
Gavin Conibeer, Haixiang Zhang, Beniamino Iandolo, Anders Hellman, Igor Zoric, and Björn Wickman
- Subjects
Fabrication ,Chemistry ,Annealing (metallurgy) ,General Chemical Engineering ,Oxygen evolution ,Nanotechnology ,General Chemistry ,Hematite ,Redox ,Anode ,Dielectric spectroscopy ,Chemical physics ,visual_art ,visual_art.visual_art_medium ,Grain boundary - Abstract
Hematite (α-Fe2O3) is a very promising material for solar water splitting that requires a high anodic potential to initiate the oxygen evolution reaction (OER). In this work, we explore the correlation between the downshift in flat band potential of hematite, Vfb, and in onset potential of OER, Vonset, caused by prolonged annealing. We observed a cathodic shift (i.e., towards lower potentials) of 200 mV of Vonset on model photoanodes consisting of ultra-thin hematite films, upon increasing the oxidation time during fabrication and without any further modifications. Detailed physical characterization, electrochemical impedance spectroscopy, and Mott-Schottky analysis revealed a quantitative correlation between the cathodic shift of Vonset and a lowering of Vfb. We identified a reduction in concentration of grain boundaries with increasing oxidation time, as the mechanism behind the observed shift of the Vfb. The approach presented here can be seen as a complementary strategy to co-catalysts and other post-fabrication treatments to lower Vonset. Moreover, it is generically applicable to photoelectrodes used to carry out oxidation and reduction half-cell reactions.
- Published
- 2015
41. The rise of hematite: origin and strategies to reduce the high onset potential for the oxygen evolution reaction
- Author
-
Anders Hellman, Igor Zoric, Beniamino Iandolo, and Björn Wickman
- Subjects
Aqueous solution ,Renewable Energy, Sustainability and the Environment ,Chemistry ,Band gap ,Oxygen evolution ,Nanotechnology ,General Chemistry ,Electrolyte ,Hematite ,visual_art ,visual_art.visual_art_medium ,Valence band ,Water splitting ,General Materials Science ,Electrochemical potential - Abstract
Hematite (alpha-Fe2O3) has emerged as a promising material for photoelectrochemical (PEC) water splitting thanks to its abundance, stability in an aqueous environment, favorable optical bandgap and position of the electronic valence band. Nevertheless, its performance as a photoanode is considerably lower than what is theoretically achievable. In particular, the high electrochemical potential usually needed to initiate water oxidation is detrimental to the prospect of using hematite for practical devices. In this review we elucidate the appealing, as well as the challenging, aspects of using hematite for PEC water splitting and focus on the recent efforts towards lowering the onset potential of water oxidation. We examine and rationalize several strategies pursued to achieve this goal involving manipulation of the hematite/electrolyte interface, as well as improving relevant properties of hematite itself.
- Published
- 2015
42. Fuel Cells: High Specific and Mass Activity for the Oxygen Reduction Reaction for Thin Film Catalysts of Sputtered Pt3 Y (Adv. Mater. Interfaces 13/2017)
- Author
-
Eleonora Zamburlini, Henrik Grönbeck, Ligang Feng, Ib Chorkendorff, Björn Wickman, Niklas Lindahl, Ifan E. L. Stephens, María Escudero-Escribano, and Christoph Langhammer
- Subjects
Materials science ,chemistry ,Chemical engineering ,Mechanics of Materials ,Mechanical Engineering ,Analytical chemistry ,chemistry.chemical_element ,Fuel cells ,Oxygen reduction reaction ,Thin film ,Platinum ,Mass activity ,Catalysis - Published
- 2017
43. Iron Oxide Films Prepared by Rapid Thermal Processing for Solar Energy Conversion
- Author
-
Andrew Burrows, Björn Wickman, A. Bastos da Silva Fanta, Beniamino Iandolo, Jakob Birkedal Wagner, and Anders Hellman
- Subjects
Multidisciplinary ,Materials science ,Iron oxide ,Mineralogy ,02 engineering and technology ,Hematite ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,7. Clean energy ,Grain size ,Article ,0104 chemical sciences ,Dielectric spectroscopy ,chemistry.chemical_compound ,chemistry ,Chemical engineering ,Rapid thermal processing ,visual_art ,Electrode ,visual_art.visual_art_medium ,Energy transformation ,Thin film ,0210 nano-technology - Abstract
Hematite is a promising and extensively investigated material for various photoelectrochemical (PEC) processes for energy conversion and storage, in particular for oxidation reactions. Thermal treatments during synthesis of hematite are found to affect the performance of hematite electrodes considerably. Herein, we present hematite thin films fabricated via one-step oxidation of Fe by rapid thermal processing (RTP). In particular, we investigate the effect of oxidation temperature on the PEC properties of hematite. Films prepared at 750 °C show the highest activity towards water oxidation. These films show the largest average grain size and the highest charge carrier density, as determined from electron microscopy and impedance spectroscopy analysis. We believe that the fast processing enabled by RTP makes this technique a preferred method for investigation of novel materials and architectures, potentially also on nanostructured electrodes, where retaining high surface area is crucial to maximize performance.
- Published
- 2017
44. Benchmarking the Stability of Oxygen Evolution Reaction Catalysts: The Importance of Monitoring Mass Losses
- Author
-
Ifan E. L. Stephens, Brian P. Knudsen, Ib Chorkendorff, Elisa Antares Paoli, Paolo Malacrida, Björn Wickman, and Rasmus Frydendal
- Subjects
Chemical engineering ,Chemistry ,Electrochemistry ,Oxygen evolution ,Analytical chemistry ,Water splitting ,Quartz crystal microbalance ,Heterogeneous catalysis ,Inductively coupled plasma mass spectrometry ,Catalysis ,Energy storage ,Corrosion - Abstract
Because of the rising need for energy storage, potentially facilitated by electrolyzers, improvements to the catalysis of the oxygen evolution reaction (OER) become increasingly relevant. Standardized protocols have been developed for determining critical figures of merit, such as the electrochemical surface area, mass activity and specific activity. Even so, when new and more active catalysts are reported, the catalyst stability tends to play a minor role. In this work, we monitor corrosion on RuO2 and MnOx by combining the electrochemical quartz crystal microbalance (EQCM) with inductively coupled plasma mass spectrometry (ICP–MS). We show that a meaningful estimation of the stability cannot be achieved based on purely electrochemical tests. On the catalysts tested, the anodic dissolution current was four orders of magnitude lower than the total current. We propose that even if long-term testing cannot be replaced, a useful evaluation of the stability can be achieved with short-term tests by using EQCM or ICP–MS.
- Published
- 2014
45. Electrochemical etching of AlGaN for the realization of thin-film devices
- Author
-
Johannes Enslin, Rinat Yapparov, Filip Hjort, Åsa Haglund, Tim Wernicke, Saulius Marcinkevicius, Michael Alexander Bergmann, Björn Wickman, and Michael Kneissl
- Subjects
010302 applied physics ,Photoluminescence ,Materials science ,Physics and Astronomy (miscellaneous) ,business.industry ,02 engineering and technology ,Surface finish ,Substrate (electronics) ,Heat sink ,021001 nanoscience & nanotechnology ,01 natural sciences ,Etching (microfabrication) ,0103 physical sciences ,Optoelectronics ,Thin film ,0210 nano-technology ,business ,Layer (electronics) ,Quantum well - Abstract
Heterogeneously integrated AlGaN epitaxial layers will be essential for future optical and electrical devices like thin-film flip-chip ultraviolet (UV) light-emitting diodes, UV vertical-cavity surface-emitting lasers, and high-electron mobility transistors on efficient heat sinks. Such AlGaN-membranes will also enable flexible and micromechanical devices. However, to develop a method to separate the AlGaN-device membranes from the substrate has proven to be challenging, in particular, for high-quality device materials, which require the use of a lattice-matched AlGaN sacrificial layer. We demonstrate an electrochemical etching method by which it is possible to achieve complete lateral etching of an AlGaN sacrificial layer with up to 50% Al-content. The influence of etching voltage and the Al-content of the sacrificial layer on the etching process is investigated. The etched N-polar surface shows the same macroscopic topography as that of the as-grown epitaxial structure, and the root-mean square roughness is 3.5 nm for 1 µm x 1 µm scan areas. Separated device layers have a well-defined thickness and smooth etched surfaces. Transferred multi-quantum-well structures were fabricated and investigated by time-resolved photoluminescence measurements. The quantum wells showed no sign of degradation caused by the thin-film process.
- Published
- 2019
46. The impact of iridium on the stability of platinum on carbon thin-film model electrodes
- Author
-
Carina Lagergren, Maria Wesselmark, Björn Wickman, and Göran Lindbergh
- Subjects
Thin layers ,Materials science ,General Chemical Engineering ,Inorganic chemistry ,Analytical chemistry ,chemistry.chemical_element ,Electrochemistry ,Underpotential deposition ,Platinum on carbon ,chemistry ,Electrode ,Reversible hydrogen electrode ,Thin film ,Platinum - Abstract
Increasing the stability and lifetime of the electrodes is one of the most important factors in order to realise a large scale use of polymer electrolyte membrane fuel cells (PEMFC). By using well-defined thin-film model electrodes, the stability of Pt and Pt on Ir were examined as cathode catalysts in a single cell PEMFC setup. The electrodes were fabricated by evaporating thin layers of Pt and Pt on Ir onto the microporous layer of a gas diffusion layer. The amount of Pt deposited was equivalent to 3 nm (about 6.3 mu g cm(-2)) and the amount of Ir was varied between 1.5 nm and 20 nm (between 3.4 mu g cm(-2) and 45.3 mu g cm(-2)). All samples with Ir showed an increased stability over samples with sole Pt during cyclic corrosion test between 0.6V and 1.2V vs. the reversible hydrogen electrode. For thin layers of Ir, the initial activity for the oxygen reduction reaction was equal to or superior to that of sole Pt but for thicker Ir films it was somewhat lower. Hydrogen underpotential deposition and CO stripping were used to estimate the electrochemical surface area during the experiments and physical characterisation using scanning electron microscopy and X-ray photoelectron spectroscopy were used to determine the structure of the samples. The results suggest that Ir can stabilise Pt in the cathode electrode. (C) 2013 Elsevier Ltd. All rights reserved.
- Published
- 2013
47. Tailoring Charge Recombination in Photoelectrodes Using Oxide Nanostructures
- Author
-
Anders Hellman, Björn Wickman, Beniamino Iandolo, Elin Svensson, and Daniel Paulsson
- Subjects
Materials science ,Oxide ,Hematite ,Bioengineering ,Nanotechnology ,02 engineering and technology ,010402 general chemistry ,01 natural sciences ,Condensed Matter::Materials Science ,chemistry.chemical_compound ,Electric field ,Photoelectrodes ,Energy transformation ,General Materials Science ,SDG 7 - Affordable and Clean Energy ,Water splitting ,Range (particle radiation) ,business.industry ,Mechanical Engineering ,General Chemistry ,Semiconductor device ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Energy conversion ,Charge recombination ,0104 chemical sciences ,Semiconductor ,chemistry ,Optoelectronics ,Charge carrier ,0210 nano-technology ,business - Abstract
Optimizing semiconductor devices for solar energy conversion requires an explicit control of the recombination of photogenerated electron−hole pairs. Here we show how the recombination of charge carriers can be controlled in semiconductor thin films by surface patterning with oxide nanodisks. The control mechanism relies on the formation of dipole-like electric fields at the interface that, depending on the field direction, attract or repel minority carriers from underneath the disks. The charge recombination rate can be controlled through the choice of oxide material and the surface coverage of nanodisks. We provide proof-of-principle demonstration of this approach by patterning the surface of Fe2O3, one of the most studied semiconductors for light-driven water splitting, with TiO2 and Cu2O nanodisks. We expect this method to be generally applicable to a range of semiconductor-based solar energy conversion devices.
- Published
- 2016
48. Mass transport effects in CO adsorption and continuous CO electrooxidation over regular arrays of Pt nanostructures on planar glassy carbon supports
- Author
-
Bengt Herbert Kasemo, Rolf Jürgen Behm, Y.E. Seidel, H Schwechten, Zenonas Jusys, M. Heinen, and Björn Wickman
- Subjects
Sticking coefficient ,Adsorption ,Standard electrode potential ,Chemistry ,General Chemical Engineering ,Diffusion ,Electrode ,Electrochemistry ,Analytical chemistry ,Reversible hydrogen electrode ,Substrate (electronics) ,Glassy carbon ,Analytical Chemistry - Abstract
The interplay between mass transport and the kinetics of CO adsorption/CO electrooxidation was studied on nanostructured electrodes, which consist of regular arrays of catalytically active cylindrical Pt nanodisks supported on a planar glassy carbon (GC) substrate, and are fabricated via Hole-mask Colloidal Lithography. CO adsorption and oxidation were measured under controlled transport conditions in a thin-layer flow cell interfaced to a mass spectrometer. The temporal evolution of the relative COad coverage, the effective sticking coefficient and the dependence of the adsorption rate on the COad coverage were evaluated for CO adsorption at 0.06 V (vs. reversible hydrogen electrode) at systematically varied CO concentrations and Pt nanodisk coverages. Continuous CO oxidation was studied at different electrode potentials under identical mass transport condition. While qualitatively, the characteristics of the adsorption/reaction kinetics do not depend on the transport conditions, the absolute rates of CO adsorption and CO (bulk) oxidation, normalized to the Pt coverage, increase strongly with decreasing Pt coverage on the nanostructured Pt/GC electrodes. This is explained by a gradual transition from one-dimensional planar diffusion (concentration gradients planar to the surface–extended Pt surface) to three-dimensional hemispherical diffusion (nanostructured surfaces).
- Published
- 2011
49. Tungsten oxide in polymer electrolyte fuel cell electrodes—A thin-film model electrode study
- Author
-
Carina Lagergren, Göran Lindbergh, Björn Wickman, and Maria Wesselmark
- Subjects
Materials science ,General Chemical Engineering ,Limiting current ,Analytical chemistry ,Proton exchange membrane fuel cell ,Electrolyte ,Conductivity ,Electrochemistry ,chemistry.chemical_compound ,chemistry ,Nafion ,Electrode ,Cyclic voltammetry - Abstract
Thin films of WO(x) and Pt on WO(x) were evaporated onto the microporous layer of a gas diffusion layer (GDL) and served as model electrodes in the polymer electrolyte fuel cell (PEFC) as well as in liquid electrolyte measurements. In order to study the effects of introducing WO, in PEFC electrodes, precise amounts of WO(x) (films ranging from 0 to 40 nm) with or without a top layer of Pt (3 nm) were prepared. The structure of the thin-film model electrodes was characterized by scanning electron microscopy and X-ray photoelectron spectroscopy prior to the electrochemical investigations. The electrodes were analyzed by cyclic voltammetry and the electrocatalytic activity for hydrogen oxidation reaction (HOR) and CO oxidation was examined. The impact of Nafion in the electrode structure was examined by comparing samples with and without Nafion solution sprayed onto the electrode. Fuel cell measurements showed an increased amount of hydrogen tungsten bronzes formed for increasing WO(x) thicknesses and that Pt affected the intercalation/deintercalation process, but not the total amount of bronzes. The oxidation of pre-adsorbed CO was shifted to lower potentials for WO(x) containing electrodes, suggesting that Pt-WO(x) is a more CO-tolerant catalyst than Pt. For the HOR. Pt on thicker films of WO(x) showed an increased limiting current, most likely originating from the increased electrochemically active surface area due to proton conductivity and hydrogen permeability in the WO(x) film. From measurements in liquid electrolyte it was seen that the system behaved very differently compared to the fuel cell measurements. This exemplifies the large differences between the liquid electrolyte and fuel cell systems. The thin-film model electrodes are shown to be a very useful tool to study the effects of introducing new materials in the PEFC catalysts. The fact that a variety of different measurements can be performed with the same electrode structure is a particular strength.
- Published
- 2011
50. Hydrogen oxidation reaction on thin platinum electrodes in the polymer electrolyte fuel cell
- Author
-
Maria Wesselmark, Göran Lindbergh, Carina Lagergren, and Björn Wickman
- Subjects
Tafel equation ,Chemistry ,Analytical chemistry ,Limiting current ,Proton exchange membrane fuel cell ,Exchange current density ,Electrolyte ,Electrochemistry ,Direct-ethanol fuel cell ,lcsh:Chemistry ,Reaction rate constant ,lcsh:Industrial electrochemistry ,lcsh:QD1-999 ,lcsh:TP250-261 - Abstract
A method for measuring the kinetics of the hydrogen oxidation reaction (HOR) in a fuel cell under enhanced mass transport conditions is presented. The measured limiting current density was roughly 1600 mA cmPt−2, corresponding to a rate constant of the forward reaction in the Tafel step of 0.14 mol m−2 s−1 at 80 °C and 90% RH. The exchange current density for the HOR was determined using the slope at low overvoltages and was found to be 770 mA cmPt−2. The high values for the limiting and exchange current densities suggest that the Pt loading in the anode catalyst can be reduced further without imposing measurable voltage loss. Keywords: Hydrogen oxidation reaction, Limiting current density, Exchange current density, PEMFC, Fuel cell, Thermal evaporation
- Published
- 2010
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