The increased demand for portable electronic devices requires batteries with high energy density, low cost, long lifecycle, nature friendly and safety. Lithium-sulphur (LiS) batteries are considered the most promising energy-storage solution for rapidly growing demand for energy. Theoretical capacity of sulphur is 1672 mAh/g that is five times higher compared to commercial lithium-ion battery. The gravimetric energy density of Li-S batteries is 2500 Wh/kg. Abundance and nontoxicity of sulphur makes Li-S batteries environmentally friendly and low-cost system for energy storage. Thanks to these qualities Li-S batteries are attractive for electromobility, portable electronic devices, stationary storage of renewable energies (solar and wind).

Research is focusing on development of cathode materials for Li-S batteries. Cathode material, consisting of sulphur, conductive material (mostly some type of carbon) and binder, is synthesised by solid state reaction or by heating reaction. Cathode material is mixed with solvent and prepared slurry is coated on aluminium foil by coating bar. We are using pure lithium as an anode and reference electrode, glassy fibre separator and organic electrolyte. Test El-Cell® is assembled in argon-filled glovebox. For electrochemical characterization we are measuring electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and galvanostatic charge/discharge.

Hydrogen is regarded as the ultimate clean power source of the future. Its application to fuel cells is a typical example. However, conventional processes of hydrogen production, such as the steam reforming and partial oxidation of natural gas and other fossil fuels, accompany simultaneous production of CO₂, which is to be reduced due to the greenhouse effect. Clean production of hydrogen, e.g. by water electrolysis using renewable energy, is not competitive with current energy costs. On the other hand, decomposition of methane produces no CO₂. Noncatalytic thermal decomposition of methane requires quite a high temperature (1200°C) in order to obtain a reasonable hydrogen yield. If the heat is supplied by burning a fossil fuel, overall CO₂ emission may not be reduced significantly. Therefore, it is necessary to use a catalyst that both lowers the temperature and increases the efficiency of the reaction.

A novelty in this topic is the catalyst that is a combination of palladium and iron-nickel oxide deposited on silica.The aim of our research is to prepare a nickel and silicon based catalyst that could be used not only as a catalyst for the thermal decomposition of methane but also for the purification of saturated hydrogen in ceramic catalytic filters. The catalytic activity of the catalyst is studied through the gas chromatography method and through kinetics and thermodynamics calculations. Silicon dioxide could function not only as a support for the catalyst but also as a filter to trap the carbon produced, since it reduces the efficiency of the catalyst and causes it to be deactivated. The catalyst should also be able to operate at relatively low temperatures of – 400 ° C.

Current references:

Recent Developments in Heterogeneous Catalysts Modelling for CO₂ Conversion to Chemicals, N Podrojková, V. Sans Sangorrin, A. Oriňak, R. Oriňaková, ChemCatChem, Vol. 12 (2020). 10.1002/cctc.201901879  

Methane Decomposition Over Modified Carbon Fibers as Effective Catalysts for Hydrogen Production, K. Sisáková, A. Oriňak, R. Oriňaková, M. Strečková, J. Patera, A. Welle, Z. Kostecká, V. Girman, (2019). 10.1007/s10562-019-02962-w 

Hydrophobicity of highly ordered nanorod polycrystalline nickel and silver surfaces, J. Macko, N. Podrojková, R. Hrdý, A. Oriňak, R. Oriňaková, J. Hubálek, J. Vojtuš, Z. Kostecká, R. M. Smith, Journal of inerals and Materials Characterization and Engineering, Vol. 07, no. 05 (2019) p. 279-293. 10.4236/jmmce.2019.75020

Effect of different crystalline phase of ZnO/Cu nanocatalysts on cellulose pyrolysis conversion to specific chemical compounds, N. Podrojková, A. Oriňak, R. Oriňaková, L. Procházková, V. Čuba, J. Patera, R. M. Smith, Cellulose, Vol. 25, no. 10 (2018) p. 5623–5642. 10.1007/s10570-018-1997-7

Catalytic activity of mono and bimetallic Zn/Cu/MWCNTs catalysts for the thermocatalyzed conversion of methane to hydrogen, B. Erdelyi, A. Oriňak, R. Oriňaková, J. Lorinčík, M. Jerigová, D. Velič, M. Mičušík, M. Omastová, R. M. Smith, V. Girman, Applied Surface Science, Vol. 396 (2017) p. 574-581. 10.1016/j.apsusc.2016.10.199

Methane Decomposition over Carbon Microfibers with Ni, Co, Cu Nanoparticles Modified Catalysts to Produce Hydrogen, K. Sisáková, A. Oriňak, Hydrogen Days 2019: Through collaboration to the deployment of H2 technologies. – Prague: Czech Hydrogen Technology Platform. 2019

·         Winner of the Best Contribution Award for her poster presentation

Carbon microfibers as a support for catalyst for thermal decomposition of methane to produce hydrogen. K. Sisáková, A. Oriňak, R. Oriňaková. International Conference on Innovative Applied Energy IAPE. – Oxford: University of Oxford, 2019

ZnO/Cu core-shell nanoparticles for CO₂ conversion to methanol. N. Podrojková, A. Oriňak, R. Oriňaková. International Conference on Innovative Applied Energy IAPE. – Oxford: University of Oxford, 2019

Synthesis of Pd-NiFe₂O₄/SiO₂ Catalyst for thermal decomposition of methane to hydrogen. K. Sisáková, A. Oriňak, R. Oriňaková. Czech and Slovak Chemistry Congress 2019, High Tatras: Czech and Slovak Chemical Society, 2019

ZnO/Cu nanocatalysts for thermochemical conversion of CO₂ to chemicals. N. Podrojková, A. Oriňak, R. Oriňaková. Czech and Slovak Chemistry Congress 2019, High Tatras: Czech and Slovak Chemical Society, 2019

Synthesis of Pd-NiFe₂O₄/SiO₂ Catalyst for thermal decomposition of methane to hydrogen. K. Sisáková, A. Oriňak, R. Oriňaková. New trends in chemistry : Trends in chemistry, research and education at Faculty of Science of P.J. Šafárik University in Košice. – Košice: Pavol Jozef Šafárik University in Košice, 2019

Core-shell Nanoparticles for CO₂ Hydrogenation to Methanol. N. Podrojková, A. Oriňak, R. Oriňaková, New trends in chemistry : Trends in chemistry, research and education at Faculty of Science of P.J. Šafárik University in Košice. – Košice: Pavol Jozef Šafárik University in Košice, 2019

Decomposition of Methane Over Carbon Microfibers Modified by Ni, Co, Cu Catalysts to Produce Hydrogen, K. Sisáková, A. Oriňak, New trends in chemistry : Trends in chemistry, research and education at Faculty of Science of P.J. Šafárik University in Košice. – Košice: Pavol Jozef Šafárik University in Košice, 2018

Catalytic Pyrolysis Conversion of Cellulose to Specific Chemical Compounds, N. Podrojková, A. Oriňak, R. Oriňaková, L. Procházková, V. Čuba, J. Patera, R. M. Smith, New trends in chemistry : Trends in chemistry, research and education at Faculty of Science of P.J. Šafárik University in Košice. – Košice: Pavol Jozef Šafárik University in Košice, 2018

The increasing average temperature of the Earth’s atmosphere is a global environmental problem which continues to grow as a consequence of a constantly rising carbon dioxide (CO₂) concentration in the atmosphere. Upper scenarios for CO₂ emissions show the rise of CO₂ concentration up to 936-1200 ppm by 2100 with global temperature increase by 3 – 5.5°C. Under the lower scenarios atmospheric CO₂ levels are forecasted to remain below 450 – 550 ppm with mean global temperature 1.5°C and an increase of global mean sea between 0.26 to 0.77 m. Hence, it is imperative to reduce the emissions of CO₂. Developing efficient methods to employ CO₂ as an abundant C1 building block to produce chemicals, materials, fuels or carbohydrates is a very attractive approach.

The most common reaction in the conversion of carbon dioxide is catalytic hydrogenation. The main product of the reaction is methanol. As a pure energy option, methanol can be used in internal combustion engines, gas turbines or fuel cells and can also lead to the formation of hydrogen through methanol vapor reformation, which is also pure fuel for energy systems. However, due to the high chemical stability of carbon dioxide and the need to overcome high levels of activation energy, specific catalysts in the carbon dioxide conversion process are needed.

One of the major catalysts used for methanol synthesis is Cu-ZnO-based catalysts, mostly Cu/ZnO/Al₂O₃, which are currently used in industry. Zinc oxide increases the life of the catalyst in methanol synthesis by removing acidic sites on the alumina phases and prevents the conversion of methanol to dimethyl ether. Although current catalysts provide high selectivity for methanol synthesis, this is still not enough. Promising structures for high methanol production are core-shell nanoparticles that can inhibit unwanted secondary reactions, such as RWGS reaction. Among the possible advantages offered by core-shell nanoparticles, three main ones can be highlighted: (1) the use of the core as a support allowing specific surface (shell) nanoarchitecture in terms of porosity, surface area, etc., resulting in improved catalytic efficiency of such layer (2) the synergy between the shell and the core to achieve higher efficiency/yield/selectivity in catalytic applications; and (3) a combination of core and shell properties towards improved/combined applications. Since these are economically advantageous materials that are still most desirable in industrial catalytic hydrogenation of carbon dioxide, the study of this type of structure is very important and may be applicable in industry in the case of high selectivity to methanol.

The aim of the research is therefore to prepare ZnO/Cu core-shell nanoparticles with different shell thicknesses, which will subsequently be used as catalysts in the process of hydrogenation of carbon dioxide to methanol. The study is focused on the effect of core-shell nanoparticles on methanol production and the mechanism and results are compared with the literature. The prepared catalysts are intended to increase selectivity towards methanol and reduce the formation of secondary reactions.

Research consists of three parts, namely (1) the preparation and characterization of particles by a two-step method; (2) chromatographic analysis of catalytic hydrogenation of CO2 to methanol with calculation of kinetic parameters and determination of reaction kinetics by differential and integral methods; (3) computational simulations using density functional theory (DFT) for the theoretical study of the ZnO/CuO interface and a better understanding of the mechanism of CO₂ hydrogenation using the studied nanoparticles. DFT calculations determine the most preferred carbon dioxide bond conformations on a given catalyst surface with calculations of the adsorption energy and reaction coordinates of the carbon dioxide conversion on the catalyst surface.

Current references:

Recent Developments in Heterogeneous Catalysts Modelling for CO₂ Conversion to Chemicals, N Podrojková, V. Sans Sangorrin, A. Oriňak, R. Oriňaková, ChemCatChem, Vol. 12 (2020). 10.1002/cctc.201901879  

Methane Decomposition Over Modified Carbon Fibers as Effective Catalysts for Hydrogen Production, K. Sisáková, A. Oriňak, R. Oriňaková, M. Strečková, J. Patera, A. Welle, Z. Kostecká, V. Girman, (2019). 10.1007/s10562-019-02962-w 

Hydrophobicity of highly ordered nanorod polycrystalline nickel and silver surfaces, J. Macko, N. Podrojková, R. Hrdý, A. Oriňak, R. Oriňaková, J. Hubálek, J. Vojtuš, Z. Kostecká, R. M. Smith, Journal of inerals and Materials Characterization and Engineering, Vol. 07, no. 05 (2019) p. 279-293. 10.4236/jmmce.2019.75020

Effect of different crystalline phase of ZnO/Cu nanocatalysts on cellulose pyrolysis conversion to specific chemical compounds, N. Podrojková, A. Oriňak, R. Oriňaková, L. Procházková, V. Čuba, J. Patera, R. M. Smith, Cellulose, Vol. 25, no. 10 (2018) p. 5623–5642. 10.1007/s10570-018-1997-7

Catalytic activity of mono and bimetallic Zn/Cu/MWCNTs catalysts for the thermocatalyzed conversion of methane to hydrogen, B. Erdelyi, A. Oriňak, R. Oriňaková, J. Lorinčík, M. Jerigová, D. Velič, M. Mičušík, M. Omastová, R. M. Smith, V. Girman, Applied Surface Science, Vol. 396 (2017) p. 574-581. 10.1016/j.apsusc.2016.10.199

Methane Decomposition over Carbon Microfibers with Ni, Co, Cu Nanoparticles Modified Catalysts to Produce Hydrogen, K. Sisáková, A. Oriňak, Hydrogen Days 2019: Through collaboration to the deployment of H2 technologies. – Prague: Czech Hydrogen Technology Platform. 2019

·         Winner of the Best Contribution Award for her poster presentation

Carbon microfibers as a support for catalyst for thermal decomposition of methane to produce hydrogen. K. Sisáková, A. Oriňak, R. Oriňaková. International Conference on Innovative Applied Energy IAPE. – Oxford: University of Oxford, 2019

ZnO/Cu core-shell nanoparticles for CO₂ conversion to methanol. N. Podrojková, A. Oriňak, R. Oriňaková. International Conference on Innovative Applied Energy IAPE. – Oxford: University of Oxford, 2019

Synthesis of Pd-NiFe₂O₄/SiO₂ Catalyst for thermal decomposition of methane to hydrogen. K. Sisáková, A. Oriňak, R. Oriňaková. Czech and Slovak Chemistry Congress 2019, High Tatras: Czech and Slovak Chemical Society, 2019

ZnO/Cu nanocatalysts for thermochemical conversion of CO₂ to chemicals. N. Podrojková, A. Oriňak, R. Oriňaková. Czech and Slovak Chemistry Congress 2019, High Tatras: Czech and Slovak Chemical Society, 2019

Synthesis of Pd-NiFe₂O₄/SiO₂ Catalyst for thermal decomposition of methane to hydrogen. K. Sisáková, A. Oriňak, R. Oriňaková. New trends in chemistry : Trends in chemistry, research and education at Faculty of Science of P.J. Šafárik University in Košice. – Košice: Pavol Jozef Šafárik University in Košice, 2019

Core-shell Nanoparticles for CO₂ Hydrogenation to Methanol. N. Podrojková, A. Oriňak, R. Oriňaková, New trends in chemistry : Trends in chemistry, research and education at Faculty of Science of P.J. Šafárik University in Košice. – Košice: Pavol Jozef Šafárik University in Košice, 2019

Decomposition of Methane Over Carbon Microfibers Modified by Ni, Co, Cu Catalysts to Produce Hydrogen, K. Sisáková, A. Oriňak, New trends in chemistry : Trends in chemistry, research and education at Faculty of Science of P.J. Šafárik University in Košice. – Košice: Pavol Jozef Šafárik University in Košice, 2018

Catalytic Pyrolysis Conversion of Cellulose to Specific Chemical Compounds, N. Podrojková, A. Oriňak, R. Oriňaková, L. Procházková, V. Čuba, J. Patera, R. M. Smith, New trends in chemistry : Trends in chemistry, research and education at Faculty of Science of P.J. Šafárik University in Košice. – Košice: Pavol Jozef Šafárik University in Košice, 2018

Diabetes mellitus is the serious metabolic disease, with rapid prevalence. According to increasing number of patients suffering for diabetes, the construction of highly sensitive, small, rapid, selective, accurate and cost-effective electrochemical sensor is called for. Our research is focused on new strategy of effective, selective, and cheap electrochemical sensors development. Mainly, we are interested in non-enzymatic glucose and insulin sensors. Our group is focused on screen printed carbon and gold microelectrodes, which lead to miniaturisation of electrochemical system. Moreover, process of working electrode modification by nanomaterials improves electroanalytical properties of used electrodes system. The main aim of our study is to reach new generation of electrochemical sensors for diabetes diagnostics and commercialisation of them.

One of the new research areas at the Department of physical chemistry is the development of a new type of electrochemical sensor, which could represent a unique method of virus detection. Rapid diagnosis of the SARS-CoV-2 virus presence is limited by the inability to perform bed side PCR, while other assays that detect viral antigens are associated with low sensitivity and specificity. Fast and accurate diagnosis is limiting for quick patient identification, assessment of his contacts and timely epidemiological intervention. Affordability is also a condition for quick diagnostics. Therefore, the present project deals with basic research aimed at the development of an electrochemical sensor that is able to efficiently and quickly detect the presence of the virus in biological fluids. Our goal is to study suitable electrode materials for the electrochemical sensors development that would be able not only qualitatively but also quantitatively to determine the amount of virus particles in a sample. The use of these sensors will ensure fast detection (bed side test), low consumption of materials needed for detection, elimination of the use of instrumental and time-consuming methods, allow patients to self-test, which will ultimately reduce the overall consumption of personal protective equipment.

After decades of developing strategies to minimize the corrosion of metallic biomaterials, there is now an increasing interest to use corrodible metals in a number of medical device applications. The term “biodegradable metal” (BM) has been used worldwide to describe these new kinds of degradable metallic biomaterials for medical applications. The recently-developed representative Mg-based BMs, Fe-based BMs and other BMs (pure W, pure Zn and its alloys, etc.).

In our research, current approaches to control their biodegradation rates to match the healing rates of the host tissues with various surface modification techniques and novel structural designs are studied along with the degradation mechanisms, cytotoxicity and haemocompatibility. Electrochemical methods including dynamic polarization test and EIS (Electrochemical Impedance Spectroscopy) are used. Surface and the composition, mechanical and biological properties of the porous powder-metallurgical samples are also determined.

In our work we deal with preparation and characterization of  metallised nanocavities (single and hybrid) were fabricated by colloid lithography followed by electrochemical deposition of Ni and subsequently Ag layers. Introductory Ni deposition step iniciates more homogenous decoration of nanocavities with Ag nanoparticles. Silver nanocavity decoration has been so performed with lower nucleation rate and with Ag nanoparticles homogeinity increase. By this, two step Ni and Ag deposition trough polystyrene nanospheres (100,300,500,700,900 nm), the various Ag surfaces were obtained. Ni layer formation in the first step of deposition enabled more precisions controlling of Ag film deposition and thus final Ag surface morphology. Prepared substrates were tested as active surfaces in SERS application. The best SERS signal enhancement was observed at 500 nm Ag nanocavities with normalized thickness Ni layer ~ 0.5. Enhancement factor has been established at value 1.078×10¹⁰; time stability was determined within 13 weeks; charge distribution at nanocavity Ag surfaces as well as reflection spectra were calculated by FDTD method. Newly prepared nanocavity surface can be applied as in SERS analysis, predominantly.

Our latest research is focused on the development of slow release fertilizers used zeolites as a building materials because of their high selectivity for NH₄⁺ during ion exchange. Natural zeolite is not ideal candidates for slow release fertilizer because of high number of undesired cations and impurities in its structure. Therefore, it is necessary to activate it, with treating it with solution of metal cations that exhibit low affinity to zeolite. Afterwards, zeolite is treated with solution of an acid and lastly it’s enriched by the solution with fertile agent present. For resulting product is important how well the selected acid removes cations from zeolite structure during the activation process. During the enrichment process there are several factors affecting the resulting amount of fertile agent in the fertilizer: temperature, contact time, agitation speed, and amount of zeolite, initial concentration and pH of the solution. Effect of these factors can be tracked by the adsorption isotherm, kinetics and diffusion models. Based on the results of these models, optimal method to prepare a slow release fertilizer can be devised. Properties of the prepared fertilizer can be studied by its solubility in water column and resulting change of conductivity of the water.

Hydrogen is considered fuel of future since it is environmentally friendly clean source of energy, has high energy density and is also renewable. Sustainable production of hydrogen by electrochemical water splitting is rather simple, however it highly depends on efficient catalysts, therefore development of non-noble-metal hydrogen-producing catalyst is essential. The research is focused on the process of electrochemical water splitting into hydrogen, with oxygen as a useful by-product. This process is environmentally friendly and very promising, but the development of suitable catalysts is needed to make this technology more accessible. The aim of the research is to develop and characterize affordable effective catalysts for the hydrogen evolution reaction based on abundant, non-noble metals. In addition to porous carbon fibers doped with transition metal nanoparticles, research also focuses on metal (nickel) foams.