Publikační činnost Institutu environmentálních technologií / Publications of Centre for Environmental Technology (9350)

Permanent URI for this collectionhttp://hdl.handle.net/10084/64706

Kolekce obsahuje bibliografické záznamy publikační činnosti (článků) akademických pracovníků Institutu environmentálních technologií (9350) v časopisech registrovaných ve Web of Science od roku 2003 po současnost.
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.

Bibliografické záznamy byly původně vytvořeny v kolekci Publikační činnost akademických pracovníků VŠB-TUO, která sleduje publikování akademických pracovníků od roku 1990.

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Now showing 1 - 20 out of 397 results

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.
Exploration of bismuth-based materials for photocatalytic decomposition of N2O
(Royal Society of Chemistry, 2024) Atri, Shalu; Uma, Sitharaman; Nagarajan, Rajamani; Gregor, Maroš; Roch, Tomáš; Filip Edelmannová, Miroslava; Reli, Martin; Kočí, Kamila; Motola, Martin; Monfort, Olivier
This work is focused on the investigation of three different Bi-based materials, i.e., CaBi2O2(CO3)(2) (CBOC), Ca4Bi6O13 (CBO), and Bi2Ce2O7 (BCO), as photocatalysts in N2O reduction. This study has emphasized the effectiveness of the bismuth ion, irrespective of its presence in different structures with self-regulating electronic and morphological properties, when employed as a photocatalyst. Monophasic CBOC, CBO, and BCO samples have been synthesized by wet-chemical methods, and they exhibit distinct morphological features such as plate-like, dumbbell-shaped, and irregularly shaped crystallites. From the UV-visible diffuse reflectance spectroscopy (DRS) data, CBO exhibits a lower optical band gap of 2.52 eV compared to CBOC (3.95 eV), which CBO is synthesized from. BCO shows the lowest optical band gap of 2.16 eV. CBO exhibits the highest photocurrent generation and the lowest value in work function measurements, following the trend as CBO > CBOC > BCO. The efficiency of the Bi-based materials in photocatalytic decomposition of N2O also follows a similar trend as observed in the photocurrent measurements, wherein the CBO sample exhibits a maximum of 10.4% decomposition of N2O under UV-A in 24 h. Oxygen vacancies in CBO and BCO have been reasoned to play a crucial role in the photocatalytic decomposition of N2O.
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.
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.
Exploring kinetics and mass transfer in photocatalytic CO2 reduction: Impact of photocatalyst loading and stirrer speed
(Elsevier, 2024) Ballari, María de los Milagros; Filip Edelmannová, Miroslava; Ricka, Rudolf; Reli, Martin; Kočí, Kamila
CO2 photocatalytic reduction is a potential and promising technology to reduce the level of the greenhouse gas in the atmosphere but also as an alternative and renewable fuel resource. However, the products yield of the reaction is still low and the identification of the optimal operating conditions that affect the process are still needed to be determined. This study investigates the impact of key operational parameters, specifically photocatalyst concentration and stirring speed, on the photocatalytic reduction of CO2 in a slurry batch photoreactor utilizing synthesized TiO2. A simplified photocatalytic kinetic model, incorporating the radiation field within the photoreactor, was developed, considering mass transfer from liquid to gas phase for the primary detected reaction products (CO, CH4, and H2). The proposed models elucidate the influence of different operating conditions on product yields. Stirring speed, controlled by a magnetic stirrer, impacts the gas-liquid mass transfer rate. Increased liquid phase stirring speed ensures faster species transport to the gas phase, with a diminishing effect beyond 900 rpm. TiO2 photocatalyst mass concentration influences the available total active surface and irradiation absorbance in the photoreactor volume. Optimal product yields were observed at the lowest tested photocatalyst concentration (0.5 g center dot L-1), indicating improved irradiation distribution and reduced particle agglomeration, resulting in higher available active surface for the reaction. The calculation model successfully predicted product yields even with lower photocatalyst concentration of 0.25 g center dot L-1, with marginal increases in predicted yields. These findings provide valuable insights for scaling up and optimizing the CO2 photocatalytic reduction process, offering a foundation for future research.
Ammonia and toluene oxidation: Mutual activating effect of copper and cerium on catalytic efficiency
(Elsevier, 2024) Górecka, Sylwia; Pacultová, Kateřina; Rokicińska, Anna; Górecki, Kamil; Kuśtrowski, Piotr; Obalová, Lucie
Copper and cerium containing hydrotalcite-like precursors Cux-Cey-Mg-Al were synthesized by mutual coprecipitation followed by calcination at 800 degrees C. The obtained mixed metal oxides were studied as catalysts for selective ammonia oxidation (NH 3 -SCO) and toluene combustion. Various techniques, such as temperatureprogrammed reduction with hydrogen, temperature -programmed desorption of toluene, scanning electron microscopy and reactive frontal chromatography were used to characterize the catalysts. Series 800-Cux-Ce2.5 showed the highest catalytic efficiency in both reactions, allowing complete NH 3 and C 7 H 8 conversion below 350 degrees C and 500 degrees C, respectively. CeO 2 crystallites (12-18 nm), as well as dispersed CuO oxide forms were found in the most active samples. Both phases affect pollutants conversion, however, for ammonia oxidation the occurrence of Cu 2+ is essential, while for toluene oxidation, the formation of Ce 4+ is sufficient. Over the most active sample (800-Cu5-Ce2.5) the complete conversion in mutual oxidation of NH 3 and toluene was achieved below 450 degrees C.
Enhancing biogas production amidst microplastic contamination in wastewater treatment systems: A strategic review
(MDPI, 2024) Otieno, Job Oliver; Cydzik-Kwiatkowska, Agnieszka; Jachimowicz, Piotr
This review highlights the significant interaction between microplastic (MP) pollution and its impact on wastewater treatment systems, focusing on optimizing biogas production. We explore various sources of MPs, including tire-derived MPs, and their introduction into wastewater environments. This review delves into the mechanical and physicochemical challenges MPs pose in treatment processes, emphasizing the need for comprehensive mitigation strategies. The biological effects of MPs on microbial consortia essential for biogas production are analyzed, particularly how these pollutants interfere with each stage of anaerobic digestion-hydrolysis, acidogenesis, acetogenesis, and methanogenesis-and, consequently, biogas generation. We examine MPs' quantitative and qualitative impacts on biogas output and production rates, uncovering how MPs disrupt microbial activity in these stages. This review also discusses novel mitigation strategies combining different sludge pretreatment methods with MPs. Our goal is to enhance the sustainability of wastewater management by promoting efficient biogas production and environmental protection in the presence of persistent MP contamination.
Evaluation of anisole hydrodeoxygenation reaction pathways over a Ni/Al2O3 catalyst
(Elsevier, 2024) Dutta, Snehasis; Shumeiko, Bogdan; Aubrecht, Jaroslav; Karásková, Kateřina; Fridrichová, Dagmar; Pacultová, Kateřina; Hlinčík, Tomáš; Kubička, David
Anisole is a model molecule for studying hydrodeoxygenation (HDO) of lignin -derived oxygenates. Here we elucidate its HDO pathway over 10 % Ni/Al2O3 catalyst. Adsorption experiments showed that anisole is adsorbed on the acidic sites of the Al2O3 . Anisole adsorption at 200 -300 degrees C is reactive in nature, and results in its demethylation. The catalyst was tested at 100 -300 degree celsius, 5 -40 bar H-2 pressure. Conversion of 78 % was obtained at 5 bar and 300 degrees C, restricted by hydrogenation -dehydrogenation equilibrium. HDO mainly starts through the ringhydrogenation pathway. This is followed by demethoxylation beyond 180 degree celsius. At 5 -12 bar, cyclohexane dehydrogenates to benzene. This was confirmed by conducting an HDO experiment with methoxycyclohexane. At lower pressure deoxygenation is favored; and demethylation is accompanied with methylation of the aromatic ring, for temperature >260 degree celsius Investigation of the initial reaction stages showed that anisole HDO on Ni/Al2O3 catalyst proceeds via two independent pathways i.e., reactive adsorption/(de)methylation and aromatic ring hydrogenation.
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.
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.
Tailoring the Li+ intercalation energy of carbon nanocage anodes via atomic Al-doping for high-performance lithium-ion batteries
(Wiley, 2024) Yu, Xingmiao; Xiang, Jianfei; Shi, Qitao; Li, Luwen; Wang, Jiaqi; Liu, Xiangqi; Zhang, Cheng; Wang, Zhipeng; Zhang, Junjin; Hu, Huimin; Bachmatiuk, Alicja; Trzebicka, Barbara; Chen, Jin; Guo, Tianxiao; Shen, Yanbin; Choi, Jinho; Huang, Cheng; Rümmeli, Mark H.
Graphitic carbon materials are widely used in lithium-ion batteries (LIBs) due to their stability and high conductivity. However, graphite anodes have low specific capacity and degrade over time, limiting their application. To meet advanced energy storage needs, high-performance graphitic carbon materials are required. Enhancing the electrochemical performance of carbon materials can be achieved through boron and nitrogen doping and incorporating 3D structures such as carbon nanocages (CNCs). In this study, aluminum (Al) is introduced into CNC lattices via chemical vapor deposition (CVD). The hollow structure of CNCs enables fast electrolyte penetration. Density functional theory (DFT) calculations show that Al doping lowers the intercalation energy of Li+. The Al-boron (B)-nitrogen (N-doped CNC (AlBN-CNC) anode demonstrates an ultrahigh rate capacity (approximate to 300 mAh g(-1) at 10 A g(-1)) and a prolonged fast-charging lifespan (862.82 mAh g(-1) at 5 A g(-1) after 1000 cycles), surpassing the N-doped or BN-doped CNCs. Al doping improves charging kinetics and structural stability. Surprisingly, AlBN-CNCs exhibit increased capacity upon cycling due to enlarged graphitic interlayer spacing. Characterization of graphitic nanostructures confirms that Al doping effectively tailors and enhances their electrochemical properties, providing a new strategy for high-capacity, fast-charging graphitic carbon anode materials for next-generation LIBs.
Factors controlling the organ-specific T1 contrast effect of silica nanoparticles co-doped with both Mn2+ ions and oleate-coated iron oxides
(Elsevier, 2024) Bochkova, Olga; Stepanov, Alexey; Bebyakina, Anastasiya; Smekalov, Daniil; Kholin, Kirill; Nizameev, Irek; Romashchenko, Alexander; Zavjalov, Evgenii; Lubina, Anna; Voloshina, Alexandra; Tyapkina, Oksana; Tarasov, Maxim; Sultanov, Timur; Rümmeli, Mark H.; Salnikov, Vadim; Budnikova, Yulia; Mustafina, Asiya
The present work introduces the synergistic effect of co-doping of both oleate-coated superparamagnetic iron oxide nanoparticles (SPIONs) and Mn(NO3)(2) into silica nanoparticles (SNs) on the T-1-relaxivity relaxivity of Mn2+ ions. The observed synergism can be attributed to the limited oxidation of Mn(2+ )ions when they are doped into the outer layer of SNs doped with SPIONs, despite the alkaline synthesis conditions. The electrochemical behaviour of the manganese ions inside co-doped SNs corroborates the predominance of their oxidation state (2+). Moreover, the T-1 relaxivities of co-doped SNs have been determined to be 20.0 mM(- 1 )s(- 1 ) and 30.0 mM(- 1 ) s(- 1 ) at 0.47 T. The T-2 relaxivity of co-doped SNs can be tuned by incorporating 6 or 13 nm SPIONs with different saturation magnetizations, which allows the T-2/T-1 2 /T (1) relaxation ratios to be limited to 0.8-5.9. The incorporation of amino groups on the surface of co-doped SNs by substituting silanol groups with propylamino groups reduces T-1 relaxivity to 9.0 mM(- 1) s(- 1) , which is nevertheless sufficient to provide a brightening of the abdominal organs and mouse brain in magnetic resonance imaging at 11.7 T. The preferential localisation of co-doped SNs in the kidneys and intestines compared to the liver is a consequence of the specificity of amino-substituted SNs compared to bare SNs.
Coordination-regulated epitaxial growth for 2D/3D perovskite vertical alignment heterostructure
(Elsevier, 2024) Zhao, Guoxiang; Chen, Yuan; Cong, Shan; Li, Lutao; Wang, Chen; Du, Xinyu; Liu, Ruirui; Lu, Jing; Liu, Yu; Chen, Gaoyuan; Zhang, Sihan; Zhang, Liya; Rümmeli, Mark H.; Zou, Guifu
In situ growth of suspended zirconene islets inside graphene pores
(Wiley, 2024) Mendes, Rafael G.; Ta, Huy Quang; Gemming, Thomas; van Gog, Heleen; van Huis, Marijn A.; Bachmatiuk, Alicja; Rümmeli, Mark H.
Experiments using a transmission electron microscope decomposed zirconium acetylacetonate with an electron beam, forming zirconium nanoparticles on graphene. Continued electron irradiation transformed these nanoparticles into atomically thick zirconium islets (zirconene islets) within the graphene lattice. The electron beam caused zirconium atom dislocations and vacancies that are rapidly refilled, a process repeating until the vacancies evolved into zirconium nanoribbons before breaking. This study offers insights into the electron-driven growth and degradation of zirconene islets, showcasing a method to fabricate freestanding zirconenes for use as atomically thin coatings in extreme environments.
Use of thermal analysis for the study of the adsorption of pharmaceuticals from water
(Elsevier, 2024) Bednárek, Jan; Šiler, Pavel; Švec, Jiří; Vráblová, Martina
The contamination of water with pharmaceuticals is one of the serious problems in the modern world. Their occurrence in surface- and groundwater brings a risk to the environment as well as human health. Therefore, many methods are studied in order of their removal. Adsorption on activated carbon belongs to the most popular ones. This paper is aimed at using thermal analysis to study the adsorption of analgesic paracetamol (acetaminophen) on activated carbon. Adsorption experiments including adsorption kinetics, adsorption isotherms, the effect of temperature and the effect of pH were also performed. Two different samples of commercial activated carbon (one powdered activated carbon (PAC) and one granular activated carbon (GAC)) and different initial concentrations of paracetamol were used. Equilibrium concentrations were determined with the aid of UV-VIS spectrophotometry and compared with thermogravimetric curves. Adsorption of paracetamol led to an appearance of a weak additional DTG peak at around 300-400 degrees C and negligible DTA effect in this temperature range. The DTG peaks at around 600 degrees C were reduced, indicating the removal of the groups left after activation on the carbon surface. The low height and width of DTG peaks and DTA effects were connected with a low mass ratio of adsorbed paracetamol related to the adsorbent mass (about 10-20%), more distinctive peaks could be achieved by the use of better adsorbing contaminants with higher molar mass.
Photocatalytic reduction of CO2 over Ti3+ self-doped TiO2-based nanomaterials
(Elsevier, 2024) Ricka, Rudolf; Wanag, Agnieszka; Kusiak-Nejman, Ewelina; Moszyński, Dariusz; Filip Edelmannová, Miroslava; Reli, Martin; Baďura, Zdeněk; Zoppellaro, Giorgio; Zbořil, Radek; Morawski, Antoni W.; Kočí, Kamila
In this study, we explored the photocatalytic efficacy of Ti3+-doped TiO2-based photocatalysts for CO2 reduction. The Ti3+ self-doped photocatalysts were synthesized using a straightforward chemical reduction with sodium borohydride (NaBH4). Our investigation aimed to elucidate the intricate interplay between the synthesis process and the quantity of NaBH4 reductant on the physical-chemical and photocatalytic attributes of the defective TiO2-based photocatalysts. We explored three different commercially available TiO2 materials labeled P25, (S) TiO2, and KRONOClean7050, which were reduced (2 g of TiO2) with 0.75 and 1.5 g of NaBH4. The reduction with 0.75 g of NaBH4 led to a significant decrease of photocatalytic activity in all three cases. It was caused by clogging of the photocatalysts surface by sodium ions which resulted in the surface recombination of charge carriers. Oppositely, the reduction with 1.5 g of NaBH4, led to an increase of the photocatalytic activity with superior performance of KRONOClean7050. The comprehensive characterization of all the samples explained this superior performance of KC7050_RED_1.5 sample. Importantly, it did not contain any amorphous phase and the crystal size was two times higher compared to other 2 samples reduced by 1.5 g of NaBH4. In the addition to higher crystallinity, the formation of a disordered TiO2_x layer, enriched with Ti3+ defects and oxygen vacancies, was confirmed. These structural features enhance the light absorption and mitigate undesired recombination of photogenerated charge carriers. These results would trigger farther investigation of defect engineering towards enhancement of the efficiency of metal oxide photocatalysts.
Synergistic effect of manganese on zirconia and ceria supports for improving photoreduction of CO2
(Elsevier, 2024) Sagar, Tatiparthi Vikram; Kumar, Praveen; Filip Edelmannová, Miroslava; Ricka, Rudolf; Reli, Martin; Kočí, Kamila; Nadrah, Peter; Emin, Saim; Sever Škapin, Andrijana; Štangar, Urška Lavrenčič
Photocatalytic CO2 reduction in the liquid phase at neutral pH conditions has been studied employing high surface area Mn-modified cubic CeO2 and amorphous ZrO2 catalysts. Results of the photocatalytic reduction of CO2 to methane are promising on Mn-modified ZrO2 and comparable with the noble metal-based photocatalysts. The surface area of both supports CeO2 and ZrO2 increased with Mn addition. Two broad diffraction peaks in Xray diffractograms indicate that the ZrO2 support is in the amorphous phase and Mn addition showed no considerable change. High intense diffraction peaks for CeO2 support illustrated the cubic fluorite phase and Mn addition to CeO2 support decreased the crystallite size due to the incorporation of Mn ions into the CeO2 lattice. XPS study revealed the stabilization of Mn in a lower oxidation state i.e., Mn2+ and Mn3+, with ZrO2 support than with CeO2 support. The superior specific capacitance of the Mn-modified ZrO2 catalyst indicates the enhanced synergy of active Mn species and support. Among the studied catalysts, Mn-modified ZrO2 photocatalyst exhibited the highest activity and selectivity for photoreduction of CO2 to methane and CO.
High-performance photoelectrochemical hydrogen production using asymmetric quantum dots
(Wiley, 2024) Wang, Kanghong; Wang, Chao; Tao, Yi; Tang, Zikun; Benetti, Daniele; Vidal, François; Liu, Yu; Rümmeli, Mark H.; Zhao, Haiguang; Rosei, Federico; Sun, Xuhui
Solar-driven photoelectrochemical (PEC) reactions using colloidal quantum dots (QDs) as photoabsorbers have shown great potential for the production of clean fuels. However, the low H2 evolution rate, consistent with low values of photocurrent density, and their limited operational stability are still the main obstacles. To address these challenges, the heterostructure engineering of asymmetric capsule-shaped CdSe/CdxZn1-xSe QDs with broad absorption and efficient charge extraction compared to pure-shell QDs is reported. By engineering the shell composition from pure ZnSe shells into CdxZn1-xSe gradient shells, the electron transfer rate increased from 4.0 × 107 s−1 to 32.7 × 107 s−1. Moreover, the capsule-shaped architecture enables more efficient spatial carrier separation, yielding a saturated current density of average of 25.4 mA cm−2 under AM 1.5 G one sun illumination. This value is the highest ever observed for QDs-based devices and comparable to the best-known Si-based devices, perovskite-based devices, and metal oxide-based devices. Furthermore, PEC devices based on heterostructured QDs maintained 96% of the initial current density after 2 h and 82% after 10 h under continuous illumination, respectively. The results represent a breakthrough in hydrogen production using heterostructured asymmetric QDs.
Virgin polymers via pyrolysis – A review of heteroatom removal options
(Elsevier, 2024) Snow, Jan; Kuráň, Pavel; Kašpárek, Aleš; Leštinský, Pavel; Suchopa, Robert
This review is dedicated to the removal of heteroatoms from plastic pyrolysis liquid products for use in the petrochemical industry. The chapters are devoted to removing individual groups of heteroatoms and summarizing the current scientific knowledge on the subject. Attention is given to the possibilities of heteroatom removal at all stages of the recycling process except sorting. Most of the findings in this area relates to the halogen removal, where high efficiencies can be achieved already in the pyrolysis process. In contrast, the removal of other heteroatoms has mainly been studied in the liquid product, usually in a hydrogen atmosphere and in the presence of a catalyst. It seems economically feasible to remove the heteroatoms as early as possible in the recycling process. This can be achieved in part by washing the waste plastic in water, which can remove a large proportion of the heteroatoms present as impurities. The work highlights the need for comprehensive mapping of heteroatoms in products and, in many cases, the need for more data regarding their removal. Finally, conclusions are drawn for further research in this area.

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