Publikační činnost Katedry chemie a fyzikálně-chemických procesů / Publications of Department of Chemistry and Physico-Chemical Processes (651)

Permanent URI for this collectionhttp://hdl.handle.net/10084/146157

Kolekce obsahuje bibliografické záznamy publikační činnosti akademických pracovníků Katedry chemie a fyzikálně-chemických procesů (651) v časopisech registrovaných ve Web of Science od roku 2022.
Do kolekce jsou zařazeny:
a) publikace, u nichž je v originálních dokumentech jako působiště autora (adresa) uvedena Vysoká škola báňská-Technická univerzita Ostrava (VŠB-TUO),
b) publikace, u nichž v originálních dokumentech není v adrese VŠB-TUO uvedena, ale autoři prokazatelně v době jejich zpracování a uveřejnění působili na VŠB-TUO.

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Now showing 1 - 20 out of 69 results

Titanium-immobilized layered HUS-7 silicate as a catalyst for photocatalytic CO2 reduction
(Wiley, 2024) Ricka, Rudolf; Amen, Tareq W. M.; Tsunoji, Nao; Reli, Martin; Filip Edelmannová, Miroslava; Kormunda, Martin; Ritz, Michal; Kočí, Kamila
Utilizing photocatalytic CO2 reduction presents a promising avenue for combating climate change and curbing greenhouse gas emissions. However, maximizing its potential hinges on the development of materials that not only enhance efficiency but also ensure process stability. Here, we introduce Hiroshima University Silicate-7 (HUS-7) with immobilized Ti species as a standout contender. Our study demonstrates the remarkable photocatalytic activity of HUS-7 in CO2 reduction, yielding substantially higher carbonaceous product yields compared to conventional titanium-based catalysts TS-1 and P25. Through thorough characterization, we elucidate that their boosted photocatalytic performance is attributed to the incorporation of isolated Ti species within the silica-based precursor, serving as potent photoinduced active sites. Moreover, our findings underscore the crucial role of the Ligand-to-Metal Charge Transfer (LMCT) process in facilitating the photoactivation of CO2 molecules, shedding new light on key mechanisms underlying photocatalytic CO2 reduction.
Thermodynamic and multi-step kinetic analysis of slow pyrolysis of natural rubber-silanised cellulose composites with 30-55 phr filler content
(Elsevier, 2026) Dobrovská, Jana; Skalková, Petra; Iudina, Elizaveta; Holešová, Sylva; Kawuloková, Monika; Janík, Róbert
Pyrolysis is a promising thermochemical process for waste reduction and energy recovery. Natural rubber (NR) composites filled with 30, 45, and 55 phr silanised cellulose (CELS) were prepared and characterised by SEM and FTIR techniques. Thermogravimetric curves for heating rates of 2, 4, 6, 8, 10, and 20 °C·min−1 were measured in an inert gas. Kinetic parameters were determined by isoconversional kinetic analysis using the Friedman model-free method and a model-based method. By applying the generalised master plot method, it was found that the pyrolysis process follows an autocatalytic mechanism involving two kinetically independent, parallel pathways, each pathway consisting of two sequential steps. The results show that silanisation of cellulose has a positive effect on composite thermal stability, but only up to a specific content of CELS. At high loadings, the resulting silica-rich ash can act as a solid acid catalyst, accelerating secondary cracking reactions during pyrolysis. Innovative approaches for determining the formal thermodynamic parameters have been presented. The first method is based on the Eyring equation and the knowledge of Eα = f(α) and Aα = f(α) from the model-free method, providing the thermodynamic parameters as a function of the entire conversion range, α. The second method is based on the results of model-based kinetic analysis. The method makes it possible to determine these parameters for individual steps of a multi-step model and, thus, to compare the energy demand, spontaneity, and change in disorder of the system in the transition state for these steps.
Raman spectroscopy as an alternative approach for prediction of silicate mineral content in sedimentary rocks
(Springer Nature, 2025) Pěgřimočová, Zuzana; Ritz, Michal
This work presents Raman spectroscopy as an alternative approach for rapid prediction of silicate mineral content in sedimentary rocks. Raman spectra of clay shale and claystone samples were measured by dispersive Raman spectrometer using the excitation laser wavelength of 633 nm. Due to the presence of strong fluorescence and overlapping bands in Raman spectra of claystones and clay shales, partial least squares regression (PLSR) was employed as a multivariate calibration method for semi-quantitative estimation of silicate mineral content. The PLSR models were developed for four predominant silicate minerals of claystones and clay shales-chlorite, muscovite, quartz and albite. The correlation coefficients for calibration and validation samples were > 0.91 and > 0.84, respectively. The root mean square error of prediction (RMSEP) ranged from 1.8 to 4.9 wt %. The developed PLSR models showed good predictive capabilities for control samples and the repeatability of measurements expressed as relative standard deviation (RSD) was < 20%. This approach has the potential to be used for rapid and non-destructive on-site estimation of chlorite, muscovite, quartz and albite content in samples of claystones and clay shales using mobile Raman instruments.
Blooming microflowers: Shaping TiO2 nanostructures via anodization in metal chloride-based electrolytes
(Elsevier, 2024) Zeng, Yilan; Valappil, Lenin Thulluvan; Satrapinskyy, Leonid; Roch, Tomáš; Plecenik, Tomáš; Gregor, Maroš; Khan, Muhammad Zubair; Pavlovský, Jiří; Reli, Martin; Motola, Martin
TiO2 microflowers, consisting of nanotubes, were generated via potentiostatic anodization in fluoride-free electrolytes infused with metal chlorides. Anodizing titanium foil at 15 V for 10 min in electrolytes containing 0.1 M of FeCl3 center dot 6H2O, CrCl3 center dot 6H2O, FeCl2 center dot 4H2O, and CuCl2 center dot 2H2O yielded nanotubes with outer diameters of approximately 30 nm, 45 nm, 50 nm, and 60 nm, respectively. The introduction of metal chloride to the electrolyte significantly altered the anodization kinetics, facilitating the growth of TiO2 microflowers. These structures consist of nanotube bundles that are of few microns in length with tunable diameters, achieved rapidly within the anodization timeframe. Microflowers formed in FeCl3 center dot 6H2O electrolyte feature high aspect ratio TiO2 nanotube bundles with smaller diameters and higher nucleation density, whereas those developed in CrCl3 center dot 6H2O, FeCl2 center dot 4H2O, and CuCl2 center dot 2H2O electrolytes exhibit less preferable morphology.
Structural modification of aluminium alloy for preparation of hydrophobic and antibacterial ZnO-based coatings
(Elsevier, 2024) Gabor, Roman; Šlamborová, Irena; Mašek, Karel; Večeř, Marek; Simha Martynková, Gražyna; Hlinka, Josef; Tokarčíková, Michaela; Motyka, Oldřich; Běčák, Petr; Seidlerová, Jana
By combining mechanical treatment of aluminium alloy with subsequent surface modification using micro-arc oxidation (MAO) technology, zinc oxide (ZnO) oxide coatings were prepared, which achieved enhanced hydrophobic properties, excellent antibacterial activity and corrosion resistance. The coatings were oxidised at different MAO discharge intensities using different frequencies. All surfaces were subjected to determination of wettability, corrosion resistance and chemical stability at 1, 7, 14, and 28 days and antibacterial activity of the coatings against the bacterial population of Staphylococcus aureus, Escherichia coli with an evaluation of population inhibition after 24 h. The surfaces mechanically modified by blasting showed a hydrophobic character; their subsequent oxidation by MAO contributed to a significant increase in hydrophobic properties. The sample with the highest Zn content (1.1 wt%), prepared at an MAO source frequency of 222 Hz, i.e. at the most intense plasma discharge, showed the most significant chemical stability in simulated body fluid (SBF) and distilled water and showed the highest antibacterial activity after 24 h. Thus, blasting of aluminium alloy surfaces and their subsequent MAO in alkaline electrolyte allows to obtain oxide coatings with antibacterial, hydrophobic and corrosion-resistant properties with the possibility of their use on surfaces with potential occurrence of harmful bacteria.
Preparation and physical properties of quaternary Mn2FeSi0.5Al0.5 alloy powders with heusler and β-Mn structures
(MDPI, 2025) Skotnicová, Kateřina; Juřica, Jan; Životský, Ondřej; Čegan,Tomáš; Hrabovská, Kamila; Matějka, Vlastimil; Zlá, Simona; Kawuloková, Monika; Chrobák, Artur
Manganese-based alloys with the composition Mn2FeZ (Z = Si, Al) have been extensively investigated in recent years due to their potential applications in spintronics. The Mn2FeSi alloy, prepared in the form of ingots, powders, or ribbons, exhibits either a cubic full-Heusler (L21) structure, an inverse-Heusler (XA) structure, or a combination of both. In contrast, the Mn2FeAl alloy has so far been synthesized only in the form of ingots, featuring a primitive cubic (beta-Mn type) structure. This study focuses on the new quaternary Mn2FeSi0.5Al0.5 alloy synthesized from pure Mn, Fe, Si, and Al powders via mechanical alloying. The elemental powders were ball-milled for 168 h with a ball-to-powder ratio of 10:1, followed by annealing at 550 degrees C, 700 degrees C, and 950 degrees C for 8 h in an argon protective atmosphere. The results demonstrate that annealing at lower temperatures (550 degrees C) led to the formation of a Heusler structure with a lattice constant of 0.5739 nm. Annealing at 700 degrees C resulted in the coexistence of several phases, including the Heusler phase and a newly developed primitive cubic beta-Mn structure. Further increasing the annealing temperature to 950 degrees C completely suppressed the Heusler phase, with the beta-Mn structure, having a lattice constant of 0.6281 nm, becoming the dominant phase. These findings confirm the possibility of tuning the structure of Mn2FeSi0.5Al0.5 alloy powder-and thereby its physical properties-by varying the annealing temperature. The sensitivity of magnetic properties to structural changes is demonstrated through magnetization curves and zero-field-cooled/field-cooled curves in the temperature range of 5 K to 300 K.
Treatment of crude oil-polluted water using CoFe2O4-doped mango (Mangifera indica) seed shell composite
(Springer Nature, 2024) Asadu, Christian O.; Ujah, Chika Oliver; Ekwueme, Benjamin Nnamdi; Ezema, Chinonso Anthony; Onah, Thomas O.; Makhkamov, Trobjon; Aka, Christian Chikezie; Ugwele, Franklin O.; Onu, Chijioke Elijah
This study investigates the potential of cobalt ferrite-doped mango seed shell (CoFe2O4-MSS) as an innovative and eco-friendly approach for the treatment of crude oil-polluted water. CoFe2O4-MSS was synthesized by impregnating carbonized mango seed shell with cobalt ferrite nanoparticles through thermal precipitation. The study systematically evaluated the adsorption capacity, kinetics, and isotherm behavior of the developed material using standard equations. Experimental results demonstrate the effectiveness of the cobalt ferrite-doped mango seed shell in adsorbing crude oil components, with high removal efficiency of 98.3% at 80 degrees C after 50 min. The crystallite sizes of raw mango seed shell and CoFe2O4-MSS are 31.8 nm and 21.3 nm, respectively. The calculated adsorption capacity stood at 55.50 mg/g, the Brunauer-Emmett-Teller surface area of CoFe2O4-MSS was 1007.4m(2)/g with a porosity distribution of 1.685 eta while the volume and pore diameter are 3.104m(3)/g and 7.212 nm, respectively. FTIR analysis revealed the presence of aliphatic, aromatic, and silicon compounds. The isotherm data matched well with Langmuir isotherm model while kinetic data fitted well with Bhattacharya-Venkobachar model. The unique properties of cobalt ferrite, a magnetic and iron-based material, combined with the abundant and biodegradable nature of mango seed shells, make this composite an attractive adsorbent for removing crude oil contaminants. This research contributes to the development of sustainable and cost-effective solutions for addressing environmental challenges posed by crude oil pollution. Also, this research has contributed immensely to the sustainable development goals of the united nation (UN-SDG) regarding environmental protection.
Microwave pyrolysis-prepared engineering carbons from corn cobs and red mombin seeds towards xylene adsorption
(Elsevier, 2024) Matějová, Lenka; Vaštyl, Michal; Jankovská, Zuzana; Cichoňová, Petra; Peikertová, Pavlína; Šeděnková, Ivana; Cruz, Gerardo Juan Francisco; Veliz, Jose Luis Solis; Kania, Ondřej
High-quality biochars/activated carbons were prepared, optimizing individual parameters of energetically-save microwave pyrolysis (raw material loading - 20 vs. 60 g, nitrogen atmosphere - flow vs. batch, ZnCl2 activation) from two agricultural wastes - corn cobs, red mombin seeds. Most promising carbons were examined for gaseous xylene adsorption and showed higher sorption capacity (similar to 250-475 mg(xylene) g(-1)) than commercial carbon (similar to 214 mg(xylene) g(-1)). ZnCl2 activation of both raw materials reduces the fixed carbon content and increases volatiles in activated carbon, suggesting microwave pyrolysis of activated feedstock should take 25 min. While biochars are microporous materials with inhomogeneous low-surface mesopore/macropore network, activated carbons are highly microporous-mesoporous. ZnCl2 activation of both raw materials contributes to formation of extensive high-surface mesopore network (with pore-size < 20 nm) and enlargement of micropore-size, but does not affect the micropore volume. ZnCl2 activation increases H-2 and decreases CH4 production. Microwave pyrolysis of larger raw material loading with ZnCl2 leads to CO2 increase. Best xylene adsorption capacity (475 mg(xylene) g(-1)) was determined for activated carbon produced from 60 g loading of corn cobs in batch nitrogen atmosphere, showing the largest micropore volume, lowest surface polarity and medium rate of graphitization. Large micropore volume, low surface polarity and high rate of graphitization of carbon are xylene sorption capacity-determining factors.
On mechanism of the synthesis of boron-doped graphitic carbon nitride
(Elsevier, 2024) Cvejn, Daniel; Starukh, Halyna; Koštejn, Martin; Peikertová, Pavlína; Praus, Petr
B-doped graphitic carbon nitrides (B-CNs) represent a promising class of materials that are potentially useful in a variety of applications. Their properties depend on the nature of the B-doping, which in turn is highly dependent on the particular chemical mechanism of B-doping formation. With this in mind, we present here the study of Bdoping achieved by the co-calcination of CN-precursor (cyanoguanidine) and B-dopant (boric acid). In this study, the structural theory of the B-CN materials produced from different ratios of CN precursor and Bdopant was derived. Our proposed structure is supported by elemental analysis, X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and nuclear magnetic resonance. Based on our results, heptazine carbon replacing tetravalent B- species near the =N+=C--N- structural unit is the dominant pattern of B doping in our co-calcined materials. The identification of the nature of the B-doping allowed us to infer the mechanism of its formation in the chemical reactions taking place during calcination.
Microporous carbonaceous adsorbent prepared from a pyrolyzed polymer
(Royal Society of Chemistry, 2024) Lang, Jaroslav; Bednárek, Jan; Ritz, Michal; Kormunda, Martin; Zelenka, Tomáš; Vaštyl, Michal; Gavlová, Anna; Kolská, Zdeňka; Férová, Marta
Emerging pollutants pose a significant health risk, and their presence in water has far-reaching consequences. Although there are several ways to decrease the levels of emerging contaminants, conventional water treatment processes are not designed for their removal. One of the more effective water treatment methods used for further micropollutant elimination is adsorption on carbonaceous materials. This work focuses on the preparation of a carbonaceous adsorbent using the pyrolysis of the polymer polyetheretherketone (PEEK). The polymer was pyrolyzed at 600 degrees C for 3 hours in an N2 atmosphere. The prepared carbonaceous material is microporous and contains surface oxygen functional groups (ethers, ketones, and aldehydes). The adsorption properties of the prepared adsorbent were tested on two pharmaceuticals: the analgesic diclofenac and antibiotic ofloxacin. In this study, kinetic and equilibrium experiments were performed. The adsorption maximum was 2.25 mg g-1 for diclofenac and 2.84 mg g-1 for ofloxacin. The pseudo-second-order model and Redlich-Peterson model best fitted both diclofenac and ofloxacin. The prepared material did not show high adsorption capacity, but the potential of the polymers as a feedstock material for pyrolysis was successfully demonstrated. This research might serve as a stepping stone towards the preparation of tailor-made adsorbents that could be used for studying adsorption mechanisms.
Enhancing porous electrodes through carbon activation of palm shell with gel activating agent
(Springer, 2024) Kandasamy, Senthil Kumar; Ramyea, R.; Tharani, S.; Michalska, Monika
Activated carbon derived from biomass offers several advantages, including high surface area, customizable pore sizes, abundance, resilience across temperatures, and cost-effectiveness. This study focuses on exploring the potential of palm shell as a renewable alternative for supercapacitor electrode materials. Specifically, it investigates the utilization of a gel composed of NaOH and PVA for activating carbon. Here, palm shell undergoes chemical activation, and its resulting activated carbon's structural and physicochemical properties are comprehensively examined using XRD, FTIR, and BET measurements. The investigation delves into the electrochemical properties using cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy of electrodes fabricated from chemically activated carbon derived from palm shells. The activated carbon enhanced a surface area of 216.062 m2 g-1 and a pore volume of 0.1468 cm3 g-1, and it is produced through the innovative approach of gel-based activation. This research highlights the potential of palm shell-derived activated carbon as a viable, sustainable, and efficient material for supercapacitor electrodes.
Influence of the chemical composition of leachates on the results of ecotoxicity tests for different slag types
(Elsevier, 2024) Pavlovský, Jiří; Seidlerová, Jana; Pěgřimočová, Zuzana; Vontorová, Jiřina; Motyka, Oldřich; Michalska, Monika; Smutná, Kateřina; Roupcová, Petra; Novák, Vlastimil; Matějka, Vlastimil; Vlček, Jozef
In this study, four ecotoxicological tests on Vibrio fischeri bacteria, Sinapis alba L. (white mustard), Daphnia magna S. (daphnia's) and earthworms were performed for three types of aqueous slag (ladle, blast furnace and converter) leachates with two-grain sizes (<4 mm, <10 mm). Concentrations of toxic elements and concentrations of Cr(VI), Ca, Na, Al, and other ions were determined. The raw slags were analyzed using X-ray fluorescence spectroscopy (XRFS), and major substances were determined by X-ray powder diffraction (XRD). The aqueous slag leachates passed ecotoxicological tests and met the required criteria, showing no toxicity to Vibrio fischeri and complying with white mustard test criteria. According to the results of the ecotoxicity tests with daphnia, the blast furnace slag samples were not ecotoxic, while two other slag samples were found to be entirely compliant. Characterization of the slags showed that the effect of element/ion leachability and slag grain size is essential. Biplot principal component analysis (PCA) showed that grain size does not significantly affect the separation of individuals on the plane. A positive correlation on toxicity was found with pH, conductivity, calcium content, dissolved content, salinity and fluoride concentration, whereas a negative correlation was found with magnesium concentration, dissolved organic carbon and potassium concentration. The effective concentration at 50% inhibition (EC50) value for Vibrio fischeri correlated with the first dimension of bivariate assessment. In summary, it was found that the investigated slags can be effectively reused as they comply with regulations and do not endanger the environment.
Ex situ Raman mapping of LiMn2O4 electrodes cycled in lithium-ion batteries
(American Chemical Society, 2024) Buchberger, Dominika A.; Hamankiewicz, Bartosz; Michalska, Monika; Głaszczka, Alicja; Czerwiński, Andrzej
In this study, we focus on the large-scale ex situ Raman mapping of LiMn2O4 (LMO) electrodes maintained at varying states of charge. A comprehensive statistical analysis has been conducted at an area of ca. 3660 mu m(2) on more than 3100 collected spectra for each LMO electrode sample. High-definition ex situ Raman maps provide profound insight into the lithiation process, offering an additional perspective on the mechanism of LMO intercalation. These maps clearly depict the coexistence of two phases, with evident phase transitions and state-of-charge gradients. The set of spectra with various state-of-charge has been successfully deconvoluted taking into account the two-phase character of the ongoing reaction. In addition, we performed the study on the samples operated for 50 cycles at the high C-rates and tracked their delithiation state and impurity formation. This technique serves as a complementary visualization and analytical tool alongside other bulk-type methods employed in battery diagnostics. Importantly, this ex situ Raman mapping approach is applicable to any electrode material exhibiting a Raman response.
Removing 65 years of approximation in rotating ring disk electrode theory with physics-informed neural networks
(American Chemical Society, 2024) Chen, Haotian; Smetana, Bedřich; Novák, Vlastimil; Zhang, Yuanmin; Sokolov, Stanislav V.; Kätelhön, Enno; Luo, Zhiyao; Zhu, Mingcheng; Compton, Richard G.
The rotating Ring Disk Electrode (RRDE), since its introduction in 1959 by Frumkin and Nekrasov, has become indispensable with diverse applications in electrochemistry, catalysis, and material science. The collection efficiency (N) is an important parameter extracted from the ring and disk currents of the RRDE, providing valuable information about reaction mechanism, kinetics, and pathways. The theoretical prediction of N is a challenging task: requiring solution of the complete convective diffusion mass transport equation with complex velocity profiles. Previous efforts, including by Albery and Bruckenstein who developed the most widely used analytical equations, heavily relied on approximations by removing radial diffusion and using approximate velocity profiles. 65 years after the introduction of RRDE, we employ a physics-informed neural network to solve the complete convective diffusion mass transport equation, to reveal the formerly neglected edge effects and velocity corrections on N, and to provide a guideline where conventional approximation is applicable.
Comparative study of photocatalysis with bulk and nanosheet graphitic carbon nitrides enhanced with silver
(Springer Nature, 2024) Michalska, Monika; Pavlovský, Jiří; Simha Martynková, Gražyna; Kratošová, Gabriela; Hornok, Viktória; Nagy, Peter B.; Novák, Vlastimil; Szabó, Tamás
The main goal of this research is to investigate the effectiveness of graphitic carbon nitride (g-C3N4, g-CN) in both bulk and nanosheet forms, which have been surface-modified with silver nanoparticles (Ag NPs), as photocatalysts for the degradation of acid orange 7 (AO7), a model dye. The photodegradation of AO7 dye molecules in water was used to test the potential photocatalytic properties of these powder materials under two different lamps with wavelengths of 368 nm (UV light) and 420 nm (VIS light). To produce Ag NPs (Ag content 0.5, 1.5, and 3 wt%) on the g-CN materials, a new synthesis route based on a wet and low-temperature method was proposed, eliminating the need for reducing agents. The photodegradation activity of the samples increased with increasing silver content, with the best photocatalytic performances achieved for bulk g-CN samples and nanosheet silver-modified samples (with the highest content of 3 wt% Ag) under UV light, i.e., more than 75% and 78%, respectively. The VIS-induced photocatalytic activity of both examined series was higher than that of UV. The highest activities of 92% and 98% were achieved for the 1.5% Ag-modified g-CN bulk and nanosheet materials. This research presents an innovative, affordable, and environmentally friendly chemical approach to synthesizing photocatalysts that can be used for degrading organic pollutants in wastewater treatment.
Enhanced electrochemical properties of multiwalled carbon nanotubes modified with silver nanoparticles for energy storage application
(Elsevier, 2024) Jain, Amrita; Michalska, Monika
This work reports an easy, straightforward, and cost-effective method to synthesize a composite material using multiwalled carbon nanotubes (MWCNTs) and silver nanoparticles (Ag NPs) for application as an electrode in supercapacitors. The objective of this work was to enhance the charge transfer mechanism in supercapacitor cells by introducing the conductive particles in the MWCNT framework. The pivotal studies, like scanning (SEM), and transmission (TEM) electron microscopy, X-ray diffraction (XRD), Raman, and X-ray photoelectron (XPS) spectroscopy confirmed the formation of the composite as well as a successful deposition of Ag NPs on MWCNT. The surface area of the composite was evaluated by using the N2 adsorption-desorption studies and it was found to be of the order of 358 m2 g-1. Electrochemical studies were performed using a two-electrode system. Magnesium ion-based polymer gel electrolyte was used as an electrolyte material. The single electrode-specific capacitance was observed to be -31.9 F g-1 with power density and energy density values of -4.4 kW kg-1 and 1.2 Wh kg-1, respectively, at a current density of 0.46 A g-1. The cell was stable up to -5000 charge-discharge cycles with -96% of capacitance retention at the end of 5000 cycles.
Photoreforming for microplastics recycling: A critical review
(Elsevier, 2024) Praus, Petr
Microplastics in the environment are a serious global problem for our society and there is a strong need to develop technologies for their removal and recycling. Photoreforming based on photocatalysis is a novel approach to convert microplastics to useful chemical compounds. In this work, the literature related to the photoreforming of microplastics was reviewed. The main product of the photoreforming was hydrogen obtained from polyethylene terephthalate (PET) and polylactic acid (PLA) with the highest yields of 113 mmol g- 1 h-1 and 95.6 mmol g- 1 h-1, respectively. The hydrogen yields were processed by the non-parametric Mann-Whitney, Kolmogorov-Smirnov, Moods median, and Kruskal-Wallis tests. The pre-treatment of microplastics before the photoreforming was not found to be a critical factor for the photoreforming. In addition, the photoreforming of PET and PLA was statistically proved to provide similar hydrogen yields. The selection of suitable photocatalysts was identified as the most important factor in the photoreforming process due to the effective separation of photoinduced electrons and holes. The reaction conditions should be optimized, especially in terms of the concentration of photocatalysts in the reaction suspensions of highly concentrated KOH or NaOH. The advantages of the photoreforming, such as reactions at ambient temperature and pressure, and the use of visible (solar) irradiation, are a challenge for further research mainly concerning the hydrogen production. More experimental data are necessary to evaluate and optimize some key parameters of this photoreforming process.
Influence of Cu incorporation on activated carbon for CO2 adsorption and electrocatalytic hydrogen evolution reaction
(Elsevier, 2024) Chang, Lee-Lee; Hu, Chechia; Huang, Chun-Chieh; Matějka, Vlastimil; Tung, Kuo-Lun
Electrocatalytic hydrogen evolution reaction (HER) and CO2 reduction reaction (CO2RR) have emerged as promising approaches toward a sustainable and green society. In this study, potassium citrate-derived activated carbon (ACK) was synthesized and incorporated with copper (Cu) for electrocatalytic reduction under CO2 and N2 flows. The ACK sample exhibited high CO2 adsorption properties to generate different carbonate species and served as an electrocatalyst after Cu incorporation. To understand the competitive reactions of HER and CO2RR, different reaction conditions were applied. Under a CO2 flow, the Cu-ACK sample revealed a high and long-term current density of single bond0.9 V, and H2 (2.642 mmol) was determined as the major product, and CH3COOH, and C2H5OH as minor products. A reaction mechanism was proposed to elucidate the reaction path for the electrocatalytic CO2RR and HER.
Quality of zinc coating formed on structural steel by hot-dip galvanizing after surface contamination
(MDPI, 2024) Vontorová, Jiřina; Mohyla, Petr; Kreislová, Kateřina
This paper deals with the evaluation of the surface of structural steel whose samples were deliberately contaminated with transparent spray primer, adhesive label glue, and welding sprays prior to hot-dip galvanizing. The galvanized samples were studied by optical microscopy, GDOES, adhesion tests, and condensation humidity tests. The effect of surface contamination on the quality of the zinc coating was found to be significant. In some cases, the zinc coating is damaged (after contamination with welding sprays), in others, it is completely absent (after contamination with spray primer or adhesive label glue).
Metal-free hybrid nanocomposites of graphitic carbon nitride and char: Synthesis, characterisation and photocatalysis under visible irradiation
(Elsevier, 2024) Smýkalová, Aneta; Kinnertová, Eva; Slovák, Václav; Praus, Petr
Background The hybrid nanocomposites of graphitic carbon nitride (g-C3N4) and char were synthesised from melamine and hydroxyethyl cellulose/glucose to obtain metal-free photocatalysts active under visible irradiation. The nanocomposites were tested for the degradation of phenol and ofloxacin. Methods The nanocomposites were characterized by elemental and thermal analysis. Their electronic properties were studied by UV–Vis and photoluminescence spectroscopy. Texture and morphology were studied by physisorption of nitrogen, X-ray diffraction, infrared spectroscopy, X-ray photoelectron spectroscopy, and by transmission electron microscopy. The photocatalytic experiments were performed under the LED irradiation of 420 nm. Significant findings Hydroxyethyl cellulose and glucose formed char which was incorporated in the g-C3N4 structure. The char acted as an electron collector enabling the separation of photoinduced electrons and holes. In this way, the photocatalytic activity of g-C3N4 increased and 96% of ofloxacin was degraded during after 120 min. In addition, in this work the total combustion of graphitic carbon nitride up to 800 oC was investigated for the first time.

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