Ulrich Kunz

Ulrich Kunz
Technische Universität Clausthal | TUC · Department of Chemical Process Engineering

Professor

About

211
Publications
32,170
Reads
How we measure 'reads'
A 'read' is counted each time someone views a publication summary (such as the title, abstract, and list of authors), clicks on a figure, or views or downloads the full-text. Learn more
3,374
Citations
Citations since 2017
56 Research Items
1511 Citations
2017201820192020202120222023050100150200250300
2017201820192020202120222023050100150200250300
2017201820192020202120222023050100150200250300
2017201820192020202120222023050100150200250300
Additional affiliations
February 1991 - present
Technische Universität Clausthal
Position
  • Professor
March 1989 - April 1991
Technische Universität Braunschweig
Position
  • Group Leader
Description
  • Research on chemical reaction Engineering and catalysis.

Publications

Publications (211)
Article
Full-text available
Microbial fuel cells are a promising technology for future wastewater treatment, as it allows cleaning and power generation simultaneously. The bottleneck of microbial fuel cells is often its cathodes because they determine the power output. Gas diffusion electrodes might overcome this bottleneck due to their low production costs and high oxygen re...
Article
Full-text available
Using electrolysis systems to degrade organics in wastewater encourages utilizing this technique to remove micropollutants (MPs) in different types of water. In this work, a cell consisting of an anode as a boron-doped diamond (BDD) electrode combined with a gas diffusion (GDE) cathode without a separator showed that MPs degradation can be effectiv...
Article
Full-text available
A system of boron-doped diamond (BDD) anode combined with a gas diffusion electrode (GDE) as a cathode is an attractive kind of electrolysis system to treat wastewater to remove organic pollutants. Depending on the operating parameters and water matrix, the kinetics of the electrochemical reaction must be defined to calculate the reaction rate cons...
Article
Full-text available
The vanadium crossover is the primary source of capacity fade in vanadium flow batteries (VFB). Available transport models for the vanadium crossover use significantly different diffusion coefficients for the vanadium species. Previously, we demonstrated that redox reactions between V³⁺ and VO2⁺ occur within cation exchange membranes. Therefore, it...
Article
Full-text available
Vanadium-ion transport through the polymer membrane results in a significant decrease in the capacity of vanadium redox flow batteries. It is assumed that five vanadium species are involved in this process. Micro X-ray absorption near-edge structure spectroscopy (micro-XANES) is a potent method to study chemical reactions during vanadium transport...
Article
Full-text available
- Final open access full text available at given DOI link - To enable the evaluation of water treatment efficiency of electrochemical advanced oxidation processes (EAOPs), an approach to remove H2O2 as a catalytic pretreatment was investigated to avoid interference in chemical oxygen demand (COD) measurements. Four wastewater types with COD and H2O...
Article
Full-text available
Electrochemical advanced oxidation processes (EAOP®) are promising technologies for the decentralized treatment of water and will be important elements in achieving a circular economy. To overcome the drawback of the high operational expenses of EAOP® systems, two novel reactors based on a next-generation boron-doped diamond (BDD) anode and a stain...
Article
The vanadium redox flow battery (VRFB) is currently a potential candidate for stationary energy storage. A major challenge is the unintended vanadium transport through the separator, which results in a fade of capacity. To overcome this issue, it is necessary to understand the transport processes in the membrane on a more fundamental level. In this...
Article
Full-text available
A core component of energy storage systems like vanadium redox flow batteries (VRFB) is the polymer electrolyte membrane (PEM). In this work, the frequently used perfluorosulfonic-acid (PFSA) membrane Nafion™ 117 and a novel poly (vinylidene difluoride) (PVDF)-based membrane are investigated. A well-known problem in VRFBs is the vanadium permeation...
Article
Full-text available
de Gewebeverstärkte Protonenaustauschermembranen (gPEM) werden durch die Verarbeitung einer Polymersuspension bestehend aus gelöstem Polyethersulfon (PES) und dispersem Polystyrol (vernetzt, sulfonyliert und sulfoniert) mit Polymergeweben hergestellt und charakterisiert. Unter Verwendung eines Gewebes aus Polyetheretherketon (PEEK) mit einer Dicke...
Article
Full-text available
Redox flow batteries such as the all-vanadium redox flow battery (VRFB) are a technical solution for storing fluctuating renewable energies on a large scale. The optimization of cells regarding performance, cycle stability as well as cost reduction are the main areas of research which aim to enable more environmentally friendly energy conversion, e...
Article
The electron paramagnetic resonance (EPR) spectra of poly(vinylidene fluoride) (PVDF) films were studied in order to identify type and intensity of trapped radicals after an electron treatment with 150 kGy in air at room temperature. The observed EPR spectra consist of superimposed spectra of eight different radicals. The individual spectra were si...
Article
Full-text available
The electrolysis of HCl to form Cl2 is an integral part of the production of polycarbonates and polyurethanes. In recent years, the direct gas-phase electrolysis was shown to be significantly more efficient than the current state-of-the-art process based on the oxidation of hydrochloric acid. Still, three phenomena significantly limit the performan...
Article
A major source of capacity fade of the common vanadium redox flow battery (VRFB) is the vanadium ion transport through the separator. However, different transport models disagree significantly in the diffusion coefficient for the different V species and the influence of different transport mechanisms. The underlying hypothesis of this work is that...
Article
Full-text available
The article describes the potential of microbial fuel cells in sewage treatment and summarizes the tasks of our project DEMO-BioBZ to unlock this potential.
Data
Supplementary material to publication Combination of magnetically actuated flexible graphite–polymer composite cathode and boron-doped diamond anode for electrochemical water softening or wastewater treatment. Muddemann et al., Electrochimica Acta, July 2020
Article
Full-text available
An electrochemical reactor based on a moving graphite–polymer composite (GPC) cathode and boron-doped diamond anode is developed and used for the electrochemical water softening and treatment of artificial vacuum toilet wastewater. The magnetically actuated cathode is designed for the in situ removal of insoluble compounds, which usually precipitat...
Article
Full-text available
The influence of process parameters on the H2O2 yield of gas diffusion electrodes (GDE) are investigated. The investigated GDEs consist of Vulcan XC72 carbon black and PTFE on gold‐plated nickel wire cloth. An electrolysis cell is used to evaluate the influence of various process parameters, such as temperature, pH value, oxygen pressure and stoich...
Article
Full-text available
The kinetics of zinc dissolution in concentrated potassium hydroxide solution were determined as a function of KOH concentration, amount of added ZnO, and temperature through linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS). The measurements were evaluated with a simplified reaction scheme in which an intermediate ZnI...
Chapter
Elektrochemische Reaktoren sind Reaktionsapparate, in denen eine Wandlung zwischen chemischer und elektrischer Energie stattfindet. Sie werden häufig und in vielfältiger Gestalt in der Chemischen Industrie, zur Metallgewinnung und in der Energietechnik eingesetzt. Im vorliegenden Beitrag werden die für elektrochemische Reaktoren spezifischen Aspekt...
Article
Full-text available
This contribution describes the effect of the quality of the catalyst coating of cathodes for wastewater treatment by microbial fuel cells (MFC). The increase in coating quality led to a strong increase in MFC performance in terms of peak power density and long-term stability. This more uniform coating was realized by an airbrush coating method for...
Article
Full-text available
Regarding the treatment of (waste)water, electroche-mical processes have various advantages over other methods. They are robust, easy to operate and flexible in case of fluctuating wastewater streams. In addition, a relatively broad spectrum of organic and inorganic impurities can be removed. This contribution provides an overview of electrochemica...
Article
Electrochemical methods offer the opportunity for in-situ generation of oxidants for wastewater treatment, as disinfectant for apparatuses and production sites as well as rocket fuel. One method well known is the electrolysis of water at boron doped diamond (BDD) anodes enabling formation of highly oxidizing OH-radicals [1]. While the BDD electrode...
Article
de Vanadium‐Redox‐Flow‐Batterien stellen eine Technologie dar, die zur Speicherung fluktuierender Energien aus Solar‐ und Windkraft eingesetzt werden kann. Um die Herstellungskosten der Batterien zur verringern, können zum Beispiel kostengünstigere Ausgangsmaterialien verwendet werden. Mithilfe von Polystyrol‐basierten Polymeren bei der Membranhers...
Article
de Bei der Aufbereitung von (Ab‐)Wasser haben elektrochemische Verfahren verschiedene Vorteile gegenüber anderen Aufbereitungsmethoden. Sie sind robust, einfach in der Betriebsführung und flexibel bei Schwankungen der Abwasserfracht. Zudem kann ein relativ breites Spektrum an organischen und anorganischen Verunreinigungen entfernt werden. Dieser Be...
Article
Full-text available
New electrochemical advanced oxidation processes (EAOPs) are becoming increasingly attractive for use in wastewater treatment. A reactor with a boron-doped diamond anode and a gas diffusion cathode seems to be a promising approach for water purification, because of the in situ generation of highly reactive species such as anodic • OH radicals and c...
Article
Full-text available
Polymer electrolyte membranes (PEM) prepared by radiation-induced graft copolymerization are investigated. For this purpose, commercial poly(ethylene-alt-tetrafluoroethylene) (ETFE) films were activated by electron beam treatment and subsequently grafted with the monomers glycidyl methacrylate (GMA), hydroxyethyl methacrylate (HEMA) and N,N′-methyl...
Technical Report
Full-text available
Nanosize dispersed platinum or platinum alloys on carbon based supports are established catalysts for fuel cells. As published, currently such catalysts are produced by batch processes solely. For this purpose, usually a dissolved platinum salt (platinum precursor) is reduced to platinum nanoparticles on the surface of the supporting carbon materia...
Article
Full-text available
The project pursued the approach of purifying wastewater using a microbial fuel cell (MFC) and simultaneously converting the COD into electricity. Starting from the laboratory scale, a pilot plant was developed and investigated on a semi-industrial scale. It should be examined whether MFCs can contribute to energy and resource efficiency increase i...
Article
Over the last several years, the removal of more than 150 micropollutants was investigated. Many pharmaceuticals are persistent and pass the conventional wastewater treatment plants (WWTP). According to literature, the removal efficiency of various pharmaceuticals is between 0 and 50 % in activated sludge processes. For a standard analgesic such as...
Article
Due to increasingly stringent environmental regulations for dealing with production residues, the purification of persistent residues have moved into research focus. Therefore, the inner recycling of process waters as a secondary raw material is getting continuously more relevant. In search for new and efficient methods to purify process waters, el...
Article
Full text available at http://ecst.ecsdl.org/content/86/4/41.full.pdf+html Abstract In addition to the technical design of hydrogen peroxide-forming gas diffusion electrodes (GDE), the process conditions significantly determine the hydrogen peroxide yield. High yields are crucial for water purification, but also for decentralized and demand-orient...
Article
Full-text available
Porous glass (PG) offers the ability to vary pore sizes and modify surfaces, allowing membranes to be tailored for a given electrochemical application. In this contribution, the application of PG in all-vanadium redox-flow batteries (VFB) and the effect of surface modification with sulfonic acid groups were investigated, and the results were compar...
Article
The improvement of redox-flow batteries requires the development of chemically stable and highly conductive separators. Porous glass membranes can be an attractive alternative to the nowadays most common polymeric membranes. Flat porous glass membranes with a pore size in the range from 2 to 50 nm and a thickness of 300 and 500 μm have been used fo...
Article
Primary zinc–air batteries are well established in the commercial market, but secondary zinc–air batteries still suffer from challenging problems. Multiple charge and discharge cycles result in zinc density migration and the formation of passivating by-products, which can ultimately change the shape of the zinc anode. This work focuses on the use o...
Article
Zinc-air batteries have a great potential to be the next generation of secondary batteries. They exhibit a high volume and mass specific power density due to the use of oxygen, which can be taken directly from air. Compared to other anodes used in rechargeable batteries, zinc offers many advantages including low cost and environmental friendliness....
Article
Full-text available
Effective methods for graphite felt (GF) treatment based on Fenton’s reagent treatment and thermal modification have been used to improve microbial fuel cell (MFC) performance. The effects of the H2O2 content in Fenton’s reagent on the performances of MFCs with two different GFs (GFD and ACN-211) have been investigated. For GFD, a maximum performan...
Article
Full-text available
In the present contribution, the behavior of sodium chloride containing electrolytes at boron-doped diamond anodes are investigated. The study is focusing on industrial process water treatment and is based on half-cell measurements (active area of the working electrode: 3.14 square centimeters) and technical laboratory electrolysis measurements (ac...
Article
Full-text available
In this study, mixtures of graphite, γ-MnO2 and MoS2 with different weight proportions (20:1:1, 30:1:2 and 30:2:1) were used in microbial fuel cells (MFCs) and the catalysts were also subjected to ultrasonication to study its influence. The data suggest that the MFC fabricated with the catalyst prepared using graphite, γ-MnO2 and MoS2 in a weight p...
Poster
Full-text available
Short-cut review about 3.5 years of development of up-scaling MFCs
Article
Microbial fuel cells (MFC) are a promising technology to enhance the power-efficiency of municipal sewage plants. Therefore, the possibilities of MFC implementation on municipal sewage treatment plants are analyzed in this contribution. A newly developed up-scaled cell design is described, each with an active area of 6,200 square centimeters respec...
Article
In this study, the mixtures of graphite, MnO2 and MoS2 with different weight proportions (20:1:1, 30:1:2 and 30:2:1) were used as oxygen reduction catalyst of MFC, and effect of the weight proportion on the power density was evaluated. The data suggested that the MFC with catalyst prepared by graphite, MnO2 and MoS2 weight proportion of 20:1:1 exhi...
Article
The vanadium redox flow battery (VRFB) is a promising electrochemical storage system for stationary megawatt-class applications. The currently limited cell area determined by the bipolar plate (BPP) could be enlarged significantly with a novel extruded large-area plate. For the first time a techno-economic assessment of VRFB in a power range of 1 M...
Article
For the improvement of microbial fuel cell (MFC) performance in real wastewater it is necessary to implement catalysts on the cathode. Graphite, MnO 2 and MoS 2 fulfill the requirements with respect to costs and activity and were evaluated in this work. These materials were prepared by dispersion of MnO 2 and/or MoS 2 and graphite in a solution of...
Article
In search for appropriate processes to enhance the efficiency of municipal sewage plants, microbial fuel cells (MFC) have moved into research focus. Due to the MFC characteristic, which is able to treat wastewater while generating power simultaneously, it is also a promising approach to change the energy balance of sewage plants – switching from th...
Article
Passivation of zinc electrodes caused by formation of oxy-products with low electrical conductivity is one of the most important phenomena which limits the current density during discharge and contributes to the poor cyclability of zinc-based batteries. The present review critically discusses the existing experimental findings related to passivatio...
Article
Carbon felt electrodes belong to the key components of redox flow batteries. The purpose of this techno-economic assessment is to uncover the production costs of PAN-and rayon-based carbon felt electrodes. Raw material costs, energy demand and the impact of processability of fiber and felt are considered. This innovative, interdisciplinary approach...
Article
Full-text available
Two single microbial fuel MFCs with different roughness (roughened and without roughened) were firstly constructed and the effect of the roughness on optimal power density was studied. It was found that the power dens of MFC with unroughened electrodes, power density. Four series stack MFCs with roughened electrodes were then constru improve power...
Article
Full-text available
For the improvement of microbial fuel cell (MFC) performance in real wastewater it is necessary to implement catalysts on the cathode. Potential electrochemical catalysts for the MFC have to be widely available and should be low cost materials. Graphite, MnO2 and MoS2 fulfill the requirements and were evaluated in this work. These materials were pr...
Article
The application of grafted membranes based on modified poly(ethylene-alt-tetrafluoroethylene) (ETFE) in redox flow-batteries is reported. In analogy to commercial Nafion® 117 based membranes ETFE backbone material provides chemical, thermal, and mechanical stability. Side chains composed of 2-hydroxyethyl methacrylate (HEMA) and glycidyl methacryla...
Article
The reaction kinetics for the liquid phase synthesis of isopropyl alcohol (IPA) from propene (P) and water (W) using a macroporous sulfonic acid ion exchange resin as catalyst were determined experimentally in a multiphase CSTR in the temperature range 398 K to 433 K at 8 MPa. This high pressure is necessary to dissolve propene in the aqueous phase...
Article
Full-text available
In the present contribution, the gas-phase electrolysis of hydrogen chloride in a polymer electrolyte membrane electrolyzer was investigated in detail. Different graphite-based bipolar plate materials were tested for this purpose with the graphite-polymer compound BMA5 being the most suitable among the tested materials regarding porosity as well as...
Article
Full-text available
The mechanical behavior of lithium-ion battery electrodes that undergo a severe capacity decrease are investigated by monitoring the out-of-plane displacement on the external surface of a pouch cell. The capacity degradation does not decrease gradually as a function of time but exhibits distinct behaviors with different causes. These are electroche...
Article
In the present contribution, the influence of varying PTFE contents in the gas diffusion lay-er (GDL) on the overall performance of a polymer electrolyte membrane (PEM) electrolyzer for gas-phase hydrogen chloride electrolysis was investigated. It was found that the water management needs to be carefully adjusted to achieve an optimal performance o...
Article
The development of a powerful, cyclically stable and electrically rechargeable zinc-oxygen battery with a three-electrode configuration is reported. A copper foam was used as stable substrate for zinc deposition in flowing potassium hydroxide electrolyte, while oxygen reduction and evolution were accomplished by a commercial silver electrode and a...
Article
The influence of externally imposed mechanical loading on lithium ion pouch cells is investigated by monitoring the capacity retention and the out-of-plane displacement on the external surface of the cells. Mechanical loading was applied by bending the electrodes prior to electrochemical treatment of the cells. Only the samples loaded with the suit...
Article
To ensure a high efficiency of 5-hydroxymethylfurfural (HMF) synthesis, improved solvents for the extraction of HMF from a reactive aqueous solution were identified using the predictive thermodynamic model COSMO-RS. Utilizing COSMO-RS as a basis for a systematic solvent selection has the advantage of potentially saving significant time and effort b...
Article
In the present contribution we investigated the influence of the acid pretreatment procedure of Nafion® 117 membranes on the resulting ionic conductivity by using electrochemical impedance spectroscopy. For this purpose, a setup allowing to measure the ionic conductivity at different temperatures, relative humidities, and contact pressures was deve...
Research
Keywords: Platinum nanoparticles, Multi-wall carbon nanotubes (CNT), Direct methanol fuel cell (DMFC), Polyol reduction, pH value, Particle size control.
Research
Keywords: Platinum nanoparticles, Multi-wall carbon nanotubes (CNT), Direct methanol fuel cell (DMFC), Polyol reduction, pH value, Particle size control