Applied and Computational Electrochemistry Group
Horizon Europe keywords:
· Artificial Intelligence and Robotics
· Batteries
· Health technologies, new tools and solutions
· Hydrogen
· Next generation computing and data technologies
· Renewable energy
Introduction of the Research Group
One of the main focuses of our group is the development and theoretical description of membranes containing synthetic receptors. These membranes coupled with electrochemical read-out schemes can be used to convert chemical signal into electrical signal. Sensors based on electrical signal are generally easy to use in practice, and their small size allows easy integration in various devices. We investigate membranes that are suitable for the determination of components that have been notoriously difficult to measure. In order to create new types of membranes and sensing principles, practical implementation must be accompanied by theoretical underpinning. Therefore, we aim to describe and understand membrane behavior using state-of-the-art simulation and machine learning methods.
Recent developments in the field of Li-ion batteries have made it possible to put more electric cars on the road, and modern Li-ion batteries can also help us store the electricity generated by renewable energy sources. The specific energy of batteries – how much energy can be stored in a given mass – is a crucial metric. The use of lead, then nickel-cadmium and nickel-metal hydride from the mid-19th century onwards, has not significantly changed this metric: with Li-ion batteries, however, specific energy is on the increase. Our group is interested in the application of non-invasive electrochemical methods to assess the state-of-health of Li-ion batteries. The combination of synergistic experimental techniques with simulation and machine learning methods can help in determining not only a snapshot of the current state but also the underlying phenomena that are responsible for the cell behavior.
Our group is also interested in the investigation of how hydrogen stored in the form of formic acid can be released in a technologically and economically viable way. Formic acid is a convenient and safe way to store, distribute and transport hydrogen. The method developed can contribute to a wide range of applications beyond hydrogen storage, from chemical applications and fuel cell technology to automotive applications. Additionally, our group develops electrochemical procedures for the analytical determination of the utilized homogeneous catalysts.
Achievements
- Ammonium ion concentrations have been measured in a physiologically relevant range using small, solid-state ion-selective electrodes. These have the advantage of eliminating the internal solution required for conventional ion-selective electrode arrangements and can be easily mass-produced and miniaturised. The prepared electrodes were tested in a differential configuration such that the two electrodes used were identical in all respects except that one did not contain an ionophore suitable for selective complexation. It was shown that the differential sensors were capable of reducing the electrochemical signal of interfering ions. Also, the detection limit was improved.- For solid-state ion-selective electrodes, it is essential that their characteristics are stable during their fabrication. One of the best electrochemical methods to investigate this is electrochemical impedance spectroscopy. However, the interpretation of spectra is often not straightforward. Therefore, using the state-of-the-art Nernst-Planck-Poisson finite element modeling, we were the first to construct a numerical model capable of describing the complex impedance of these electrodes. The numerical simulations were used to train machine learning algorithms for the impedance response expected for a given set of input parameters. In this way we were able to speed up the parameter fitting to the measured results by five orders of magnitude.
- In order to understand and accurately model the amperometric and potentiometric response of electrochemical sensors, two fundamental quantities are required: one is the membrane selectivity and the other is the diffusion coefficient of ions in the membrane. Therefore, potentiometric ion diffusion experiments were performed. In which we used an ion-selective membrane that has not yet been in contact with the ion with which the ionophore forms a selective complex (primary ion). After recording the baseline, primary ions are introduced into the solution at one side of the ion selective membrane and the potential response is recorded. Here again, the state-of-the-art theoretical description of ion-selective membranes is based on the Nernst-Planck-Poisson finite-element method. The theoretical simulations have allowed us to understand how the potential signal obtained during the breakthrough experiment is affected by the different parameters. This allowed, for the first time, the independent determination of the diffusion coefficient of all ions in an ion-selective membrane.
- The behavior of Li-ion batteries has been investigated by experimental methods and predicted by computational methods. The fast processes could be described by electrochemical impedance spectroscopy measurements, while the PITT (potentiostatic intermittent titration technique) measurement procedure was used to reveal the long-term behavior of the cell. The widely used Li-ion battery simulation method, the Doyle-Fuller-Newman model, was complemented with machine learning techniques to predict and interpret both large and small time constant processes in a predictive and fast way.
Publications
Effect of Kinetic and Thermodynamic Properties of Solid Contact Ion-Selective Electrodes on the Electrochemical Impedance Spectroscopy Response, MM Kovács, L Höfler, 2022, Journal of The Electrochemical Society 169 (2), 026509, https://iopscience.iop.org/article/10.1149/1945-7111/ac4dae/metaDialysis membranes as liquid junction materials: Simplified model based on the phase boundary potential, T Forrest, L Höfler, E Bakker, 2022, Journal of Electroanalytical Chemistry 904, 115886, https://www.sciencedirect.com/science/article/pii/S1572665721009127
Application of Potentiometric Ion-Breakthrough to Assess Individual Diffusion Coefficients of Ions in Ion-Selective Membranes, D Pocsai, L Höfler, 2020, Journal of The Electrochemical Society 167 (14), 147506, https://iopscience.iop.org/article/10.1149/1945-7111/abc35c/meta
Lowering Detection Limits Toward Target Ions Using Quasi-Symmetric Polymeric Ion-Selective Membranes Combined with Amperometric Measurements, X Nagy, L Höfler, 2016, Analytical Chemistry 88 (19), 9850–9855, https://pubs.acs.org/doi/abs/10.1021/acs.analchem.6b03043
Nanosensors lost in space. A random walk study of single molecule detection with single-nanopore sensors, L Höfler, RE Gyurcsányi, 2012, Analytica chimica acta 722, 119-126, https://www.sciencedirect.com/science/article/abs/pii/S0003267012002619
Patents
Nitric oxide delivery devices, L Hofler, ME Meyerhoff, D Koley, US Patent 9,872,953 Nitric oxide (NO) has been shown to have several important physiological functions, including its unique vasodilating properties, cancer-fighting potency, anti-platelet activity, and anti-microbial/anti-viral activity. In some instances, NO can be used to control infection, prevent biofilm formation, and minimize inflammation and fibrosis. Although NO is a stable radical, it is highly reactive with hemoglobin and oxygen, thus making delivery of NO to the target site challenging. In the device described in the patent, the nitric oxide is electrochemically generated by the reduction of nitrite ions by Cu(I) ions, which are generated at the surface of a working electrode that is made of a copper containing conductive material, or a base material coated with a copper containing conductive material. Nitric oxide delivery devices, ME Meyerhoff, L Hofler, D Koley, H Ren, US Patent 10,543,337 Here, nitric oxide is also produced from nitrite ion in this device, but the catalyst is a Cu(II) complex.Awards
The course "Electrochemical Energy Storage Devices" taught at the Budapest University of Technology and Economics is ranked in the top 10% of the university, according to anonymous student opinions, 2014-2021. Junior Prima Award, Hungarian Development Bank/Hungarian Academy of Sciences, 2014Journals
Analytical Chemistry (D1)Journal of The Electrochemical Society (D1)
Journal of Electroanalytical Chemistry (Q1)
Projects
Membranes in electrochemistry, OTKA, 2017-2022, NKFIIndustry relations
Volkswagen AGSiemens
TÜV Rheinland
AVL
Pion Inc.
Conferences
Mátrafüred 2019 International Conference on Chemical Sensors, Visegrád, 2019, Lajos HöflerElectrochemistry V4 Workshop, Pécs, 2021, Lajos Höfler
KÉMIAI SZENZOROK WORKSHOP VII, Pécs, 2021, Lajos Höfler
Mátrafüred 2022 International Conference on Chemical Sensors, Visegrád, 2022, Lajos Höfler
XXII. KÖRNYEZETVÉDELMI ÉS IPARBIZTONSÁGI KONFERENCIA, Visegrád, 2022, Lajos Höfler