A5030228814- Electrocatalysts for Energy Conversion
- Fuel Cells and Related Materials
- Catalytic Processes in Materials Science
- Advanced battery technologies research
- Advancements in Solid Oxide Fuel Cells
- Nanomaterials for catalytic reactions
- Electrochemical Analysis and Applications
- Gold and Silver Nanoparticles Synthesis and Applications
- Surfactants and Colloidal Systems
- Machine Learning in Materials Science
- Electron and X-Ray Spectroscopy Techniques
- X-ray Diffraction in Crystallography
- Corrosion Behavior and Inhibition
- CO2 Reduction Techniques and Catalysts
- Geology and Paleoclimatology Research
- Geomagnetism and Paleomagnetism Studies
- Conducting polymers and applications
- Advanced Cellulose Research Studies
- Iron oxide chemistry and applications
- nanoparticles nucleation surface interactions
- Chemistry and Chemical Engineering
- Polymer Nanocomposites and Properties
- Geological formations and processes
- Advanced Thermoelectric Materials and Devices
- Nanoparticles: synthesis and applications
Stanford University
2022-2024
SLAC National Accelerator Laboratory
2022-2024
University of Bern
2020-2023
Interface (United States)
2022-2023
University of Bremen
2018-2021
University of Twente
1986
Hydrogen production from renewable resources and its reconversion into electricity are two important pillars toward a more sustainable energy use. The efficiency viability of these technologies heavily rely on active stable electrocatalysts. Basic research to develop superior electrocatalysts is commonly performed in conventional electrochemical setups such as rotating disk electrode (RDE) configuration or H-type cells. These experiments easy set up; however, there large gap real conversion...
CO2 electrolysis converts the greenhouse gas into valuable fuels and chemicals, such as carbon monoxide, ethylene, ethanol, etc. Currently, Cu is only known monometallic catalyst capable of producing multicarbon products from electrochemical reduction reaction (eCO2RR), while poor selectivity limits its further use. It has been found that introducing Ag atoms lattice can modulate product preference. However, synergistic effects between Ag, thus, catalytic performance, are strongly influenced...
Abstract Gas diffusion electrode (GDE) setups have very recently received increasing attention as a fast and straightforward tool for testing the oxygen reduction reaction (ORR) activity of surface area proton exchange membrane fuel cell (PEMFC) catalysts under more realistic conditions. In work presented here, we demonstrate that our introduced GDE setup is suitable benchmarking stability PEMFC well. Based on obtained results, it argued offers inherent advantages accelerated degradation...
Iridium nanoparticles are important catalysts for several chemical and energy conversion reactions. Studies of iridium have also been a key the development kinetic models nanomaterial formation. However, compared to other metals such as gold or platinum, knowledge on nature prenucleation species structural insights into resultant missing, especially obtained from IrxCly precursors investigated here. We use in situ X-ray total scattering (TS) experiments with pair distribution function (PDF)...
A new approach for efficiently investigating the degradation of fuel cell catalysts under realistic conditions is presented combining accelerated stress tests (ASTs) in a gas diffusion electrode (GDE) setup with small angle X-ray scattering (SAXS). GDE setups were recently introduced as novel testing tool advantages classical electrochemical cells three-electrode and membrane assemblies (MEAs). SAXS characterization catalyst layer enables an evaluation particle size distribution its changes...
In recent years, extensive research has been performed concerning the stability of fuel cell catalysts in an acidic environment. By comparison, only few studies address degradation mechanism(s) alkaline media. this work, we investigate four different types Pt/C upon applying accelerated tests a gas diffusion electrode (GDE) setup equipped with anion exchange membrane. contrast to previous investigations exposing liquid electrolyte, GDE provides realistic three-phase boundary reactant gas,...
A combination of operando small- and wide-angle X-ray scattering is here presented to provide insights into the changes in mean particle sizes phase fractions fuel cell catalyst layers during accelerated stress tests (ASTs). As a catalyst, bimodal Pt/C was chosen that consists two distinguishable size populations. The presence different should favor uncover electrochemical Ostwald ripening as degradation mechanism, is, growth larger particles at expense smaller via formation ionic metal...
State-of-the-art industrial electrocatalysts for the oxygen evolution reaction (OER) under acidic conditions are Ir-based. Considering scarce supply of Ir, it is imperative to use precious metal as efficiently possible. In this work, we immobilized ultrasmall Ir and Ir0.4Ru0.6 nanoparticles on two different supports maximize their dispersion. One high-surface-area carbon support serves a reference but has limited technological relevance due its lack stability. The other support,...
Surfactant-free UV-induced syntheses of Pt and Ir nanoparticles in alkaline methanol ethanol are presented. Small size ca. 2 nm diameter obtained without surfactants a wide range base concentration.
Water electrolysis is a pivotal technology to drive the energy transition towards system based on renewable resources. The scarce Ir crucial element for synthesis of heterogeneous catalysts oxygen evolution reaction (OER). Carbon supported oxide obtained from surfactant-free colloidal nanoparticles (NPs) synthesized in alkaline methanol (MeOH), ethanol (EtOH), and ethylene glycol (EG) are investigated compared. comparison independent techniques such as electron microscopy (TEM), small angle...
Abstract The synthesis of “surfactant‐free” Pt nanoparticles (NPs) in alkaline ethylene glycol (EG), initially introduced 2000, is fundamental interest for the preparation catalysts. Often a suspension colloidal NPs prepared by this method stored and upon demand further processed to obtain supported catalysts such as Pt−C or Pt−Al 2 O 3 . In study it shown that suspensions presence halides, e. g. from metal precursor salt, leaching takes place. Metal poses significant challenge catalyst...
Understanding the formation of nanomaterials down to atomic level is key rational design advanced materials. Despite their widespread use and intensive study over years, detailed mechanism platinum (Pt) nanoparticles remains challenging explore rationalize. Here, various in situ characterization techniques, particular X-ray total scattering with pair distribution function (PDF) analysis, are used follow structural chemical changes taking place during a surfactant-free synthesis Pt alkaline...
The influence of different combinations accelerated stress test (AST) protocols simulating load-cycle and start/stop conditions a proton exchange membrane fuel cell (PEMFC) vehicle is investigated on bimodal Pt/C catalyst. catalyst, prepared by mixing two commercial catalysts, serves as model system consists distinguishable size populations. change in mean particle was situ small-angle X-ray scattering (SAXS). comparison to the reference i.e., single-size population uncovers presence...
The alkaline polyol synthesis of "surfactant-free" Pt nanoparticles (NPs) is a straightforward approach to synthesize NPs as colloids. Even challenges such size control have been successfully addressed in the recent past, but reduction mechanism remains poorly understood. This work shows that precursors H2PtCl6 and H2PtBr6 can be performed at low reaction rates using visible light even though neither precursor nor solvent exhibits any detectable absorption range. possibility slowed down...
Sustainable electricity generation via hydrogen fuel cells requires the development of efficient oxygen reduction reaction (ORR) catalysts. In situ/operando experiments are necessary to uncover extent dynamic material changes during catalysis. Herein, we use in X-ray absorption near-edge spectroscopy track Mn valence a promising, ultrathin, porous MnOx layer on Ag thin film. Mn–K-edge measurements as function electrochemical environment and ORR conditions reveal that, interestingly, when...
Abstract Small-angle X-ray scattering (SAXS) is a powerful technique to investigate the degradation of catalyst materials. Ideally such investigations are performed operando , i.e. during catalytic reaction. An example measurements observe fuel cell catalysts an accelerated stress test (AST). Fuel consist Pt or alloy nanoparticles (NPs) supported on high surface area carbon. A key challenge SAXS proper background subtraction carbon support extract information size distribution NPs as...
Herein, we report a straightforward approach for the
Electrocatalysts enable the efficient conversion of molecules for applications in energy devices, but due to their material stability, electrochemical performance tends change over time under operating conditions. For oxygen reduction reaction (ORR), transition metal x-ides (oxides, nitrides, sulfides) are a class highly tunable, low-cost catalysts being considered as possible alternatives expensive Pt-based materials. In this work, we take multimodal characterization approach investigate...
Abstract Thermoreversible gels of cellulose acetate can be obtained by cooling concentrated solutions in solvent‐nonsolvent mixtures dioxane and water. Upon heating the gels, endothermic effects were observed with differential scanning calorimetry. The heat are ascribed to melting a crystalline phase consisting triacetate units. peaks appear only after long aging periods up several days. Melting points generally decrease heats increase increasing polymer concentration nonsolvent content....
The polyol synthesis is a well-established method to form so-called “surfactant-free” nanoparticles (NPs). In the present study, NP size resulting from thermal reduction of precursors H2PtCl6, H2Pt(OH)6, or Pt(acac)2 in presence bases NaOH Na(acac) at different concentrations studied. It shown that control depends more strongly on nature precursor (metal salt) than anion base. latter surprising as concentration base often an important factor achieve control. H2PtCl6 H2Pt(OH)6 and confirm...
Electrochemical alcohol oxidation is an attractive reaction for renewable-energy driven production of value-added chemicals, like precursors acrylic (acrolein from glycerol) and nylon (adipic acid cyclohexanol). Implementing selective, earth-abundant catalysts can improve electrolyzer efficiency economics. For example, replacing the energy intensive oxygen evolution (OER) in CO 2 electrolyzers with decrease operating voltage by about 0.85 V reduce electricity requirements up to 53% while...
Water electrolyzers, such as proton exchange membrane water electrolyzers (PEM) and anion (AEM) are important technologies for sustainable electrochemical energy conversion. The oxygen evolution reaction (OER) at the anode is a pivotal half-reaction in these systems. Despite substantial progress over years, OER kinetics remain major source of inefficiency devices, necessitating development stable catalysts. Currently, precious metal-based catalysts dominate landscape devices. As non-precious...