A5050210336- Graphene research and applications
- Nonlinear Dynamics and Pattern Formation
- Electrochemical Analysis and Applications
- Electrochemical sensors and biosensors
- Conducting polymers and applications
- Slime Mold and Myxomycetes Research
- Microfluidic and Bio-sensing Technologies
- Force Microscopy Techniques and Applications
- Advancements in Battery Materials
- Supercapacitor Materials and Fabrication
- Corrosion Behavior and Inhibition
- Electrowetting and Microfluidic Technologies
- Hydrogen embrittlement and corrosion behaviors in metals
- Analytical Chemistry and Sensors
- Dielectric materials and actuators
- Spectroscopy and Quantum Chemical Studies
- Advanced Sensor and Energy Harvesting Materials
- stochastic dynamics and bifurcation
- Advanced Battery Technologies Research
- Graphene and Nanomaterials Applications
- Photonic Crystals and Applications
- Photonic and Optical Devices
- Nanopore and Nanochannel Transport Studies
- Microfluidic and Capillary Electrophoresis Applications
- TiO2 Photocatalysis and Solar Cells
Helmholtz-Institute Ulm
2021-2022
Karlsruhe Institute of Technology
2017-2021
Princeton University
2008-2018
Vorbeck (United States)
2013-2016
Princeton Public Schools
2014
University of Duisburg-Essen
2011
New Jersey Institute of Technology
2008
Fritz Haber Institute of the Max Planck Society
2004-2008
University of Virginia
2004
When applied on the counter electrode of a dye-sensitized solar cell, functionalized graphene sheets with oxygen-containing sites perform comparably to platinum (conversion efficiencies 5.0 and 5.5%, respectively, at 100 mW cm−2 AM1.5G simulated light). To interpret catalytic activity toward reduction triiodide, we propose new electrochemical impedance spectroscopy equivalent circuit that matches observed spectra features appropriate phenomena. Using cyclic voltammetry, also show tuning our...
Abstract This roadmap presents the transformational research ideas proposed by “BATTERY 2030+,” European large‐scale initiative for future battery chemistries. A “chemistry‐neutral” to advance research, particularly at low technology readiness levels, is outlined, with a time horizon of more than ten years. The centered around six themes: 1) accelerated materials discovery platform, 2) interface genome, integration smart functionalities such as 3) sensing and 4) self‐healing processes....
Stainless steels undergo a sharp rise in pitting corrosion rate as the potential, solution concentration, or temperature is changed only slightly. We report experiments using real-time microscopic situ visualizations that resolve nucleation and evolution of individual pits during transition. They suggest sudden onset explained by an explosive autocatalytic growth number metastable stabilization takes place later. This finding agrees with theoretical approach treating cooperative critical...
For many applications of dielectric elastomer actuators, it is desirable to replace the carbon-grease electrodes with stretchable, solid-state electrodes. Here, we attach thin layers a conducting silicone prestrained films an acrylic and achieve voltage-actuated areal strains over 70%. The influence stiffness prestrain studied experimentally theoretically.
We study the effect of carbon to oxygen ratio (C/O) on electrical resistance functionalized graphene sheets prepared by thermal exfoliation and reduction graphite oxide at various temperatures. Using a 2-probe technique in conjunction with Kelvin probe force microscopy, we observe transition from high-resistance (>400 kΩ/sq) nonlinear current/voltage characteristics low C/O low-resistance (<10 linear behavior high C/O, indicating hopping diffusive electron transport....
Abstract Graphene‐based electrodes have recently gained popularity due to their superior electrochemical properties. However, the exact mechanisms of activity are not yet understood. Here, we present data from NADH oxidation and ferri/ferrocyanide redox probe experiments demonstrate that both (i) porosity graphene electrodes, as effected by packing morphology, (ii) functional group lattice defect concentration play a significant role on performance.
Electrodes used in electroanalysis, which are based on carbonaceous nanomaterials such as carbon nanotubes or graphene, often exhibit large degrees of porosity. By systematically varying the morphology functionalized graphene electrodes from nearly flat to highly porous, we demonstrate experimentally that minute amounts electrode porosity have surprisingly significant effects apparent reaction kinetics determined by cyclic voltammetry, both reversible and irreversible regime. We quantify...
The colloidal stability of functionalized graphene sheets (FGSs) in aqueous sodium dodecyl sulfate (SDS) solutions different concentrations was studied by optical microscopy and ultraviolet-visible light absorption after first dispersing the FGSs ultrasonically. In up to ∼10 μM SDS solutions, reaggregated within a few minutes, forming ramified structures absence increasingly compact as amount increased. Above μM, rate reaggregation decreased with increasing concentration; above ∼40...
We use colloidal gels of graphene oxide in a water-ethanol-ionic liquid solution to assemble graphene-ionic laminated structures for as electrodes electrochemical double layer capacitors. Our process involves evaporation water and ethanol yielding oxide/ionic composite, followed by thermal reduction the electrically conducting functionalized graphene. This yields an electrode which ionic serves not only working electrolyte but also spacer separate sheets increase their electrolyte-accessible...
We studied the local voltage drop in functionalized graphene sheets of subμm size under external bias conditions by Kelvin probe force microscopy. Using this noninvasive experimental approach, we measured ohmic current-voltage characteristics and an intrinsic conductivity about 3.7 × 10(5) S/m corresponding to a sheet resistance 2.7 kΩ/sq ambient for produced via thermal reduction graphite oxide. The contact resistivity between metal electrode was found be <6.3 10(-7) Ωcm(2).
Experiments on the voltage-induced buckling instability of thin, flexible plates to pump fluids within a microfluidic channel.
We report on the adsorption of sodium dodecyl sulfate (SDS) onto functionalized graphene sheets (FGSs) in an aqueous system, measured at broad SDS and FGS concentration ranges by conductometric surfactant titration. At dilute concentrations (<12 μM bulk solution), there is evidence a counterion exchange between hydronium ions (from dissociation acidic chemical functionalities FGS) coadsorbing with monomers FGSs. find that, for carbon-to-oxygen ratio ~18, monolayer reaches full surface...
We present a general method for characterizing the intrinsic electrochemical properties of graphene sheets, such as specific double-layer capacitance, in absence porosity-related artifacts and uncertainties. By assembling densely tiled monolayers electrically insulating or conductive functionalized sheets onto electrode substrates (gold highly oriented pyrolytic graphite), we demonstrate our ability to isolate their response terms surface-specific capacitance redox behavior. Using this...
The intrinsic electrocatalytic properties of functionalized graphene sheets (FGSs) in nitric oxide (NO) sensing are determined by cyclic voltammetry with FGS monolayer electrodes. degrees reduction and defectiveness the FGSs varied employing different heat treatments during their fabrication. intermediate high Raman ID to IG peak ratios exhibit an NO oxidation potential 794 mV (vs 1 M Ag/AgCl), closely matching values obtained a platinized Pt control (791 mV) as well recent results from...
Current density inhomogeneities on electrodes (of physical, chemical, or optical origin) induce long-range electrohydrodynamic fluid motion directed toward the regions of higher current density. Here, we analyze flow and its implications for orderly arrangement colloidal particles as effected by this patterned electrodes. A scaling analysis indicates that velocity is proportional to product applied voltage difference in between adjacent electrode. Exact analytical solutions streamlines are...
We have developed electrically conducting silicone elastomer nanocomposites that serve both as compliant electrodes in an electrostatic actuator and, at the same time, optically active elements creating structural color. demonstrate capabilities of our setup by actuating elastomeric diffraction grating and colloidal-crystal-based photonic structures.
We report on an optical microscopy technique for the analysis of corrosion kinetics metal thin films in microreactor systems and use it to study role cetyltrimethylammonium bromide surfactant as a inhibitor copper−gold galvanic coplanar microsystem. A minimum dissolution rate copper is observed when concentration ∼0.8 mM. To explain why inhibitory does not extend higher concentrations, we zero resistance ammetry with separated half cells show that while inhibits cathodic reactions gold, also...
We contrast the performance of monolayer electrodes and thin porous film highly reduced functionalized graphene to demonstrate that introduction electrode porosity gives rise strong apparent electrocatalytic effects resulting in vastly improved selectivity. This is despite showing no intrinsic advantage over glassy carbon when used as a monolayer. The simultaneous electro-oxidation ascorbic acid, dopamine, uric acid an experimental model electrolyte system. Our results suggest large number...
In situ observations of pitting corrosion as it spreads across the surface stainless steel were carried out. We apply two different imaging methods simultaneously, viz., ellipsomicroscopy for visualizing changes film properties and contrast-enhanced microscopy monitoring nucleation reactivation metastable pits. A correlation between oxide weakening caused by individual pits subsequent was found. The existence front propagation a component transition to shows that characteristics this process...
Resonant periodic forcing is applied to catalytic CO oxidation on platinum (110) in the oscillatory regime. The external parameters are chosen such that unperturbed system spontaneously develops chemical turbulence. By periodically modulating partial pressure, changes spatiotemporal behaviour of can be induced: turbulent suppressed and frequency locked patterns with sub-harmonic entrainment develop. A novel gas-driving compressor has been implemented perform experimental work.
Electrolyte-gated, printed field-effect transistors exhibit high charge carrier densities in the channel and thus on-currents at low operating voltages, allowing for low-power operation of such devices. This behavior is due to area-specific capacitance device, which electrolyte takes role dielectric layer classical architectures. In this paper, we investigate intrinsic double-layer capacitances ink-jet electrolyte-gated inorganic both in-plane top-gate architectures by means...
Spatiotemporal patterns occurring during the catalytic oxidation of carbon monoxide on Pt(110) show a strong anisotropy due to differences in diffusion coefficients along two major crystallographic axes catalyst: Reaction waves propagating parallel missing rows reconstructed Pt surface are much faster than reaction perpendicular direction. In this Article, we report observation that, as function exposure reactant gases, propagation velocities change drastically, resulting complete reversal...
While graphene and other carbonaceous nanomaterials have shown promise in a variety of electrochemical applications, measurement their intrinsic performance is often confounded with effects related to the complexities due diffusion porous medium. To by-pass this limitation, we use effectively non-porous tiled monolayers reduced oxide as model platform study how rates heterogeneous electron transfer evolve function structure/chemistry. A systems are investigated including standard...
Reflection anisotropy microscopy (RAM) is a tool to monitor the optical of surfaces with spatial resolution (Rotermund et al 1995 Science 270 608–10). It has been applied pattern formation during CO oxidation on Pt(110), where it provides high sensitivity for surface reconstruction and partially also coverage reaction educts (Heumann 2000 Dissertation TU-Berlin). However, RAM alignment procedure components were not satisfactory. Here, we give detailed description new set-up, which employs...