Effect of metalic and metal-oxide catalysts on LiAlH4 decomposition

Metal and complex light hydrides are the best fitted materials for hydrogen storage within the concept of hydrogen based economy [1]. They meet the basic application requirements: low-cost, safety and they are environmentally friendly. Beside their benefits, as relatively stable compounds, these materials exhibit also some undesirable properties like sluggish kinetics and high temperature of hydrogen desorption. LiAlH4 has emerged as a potential material for solid-state hydrogen storage because of its high hydrogen gravimetric capacity (10.5 wt%). It decomposes in three steps, according to the reactions [2]: 3LiAlH4 → Li3AlH6 + 2Al + H2 (R1) Li3AlH6 → 3LiH + Al + 3/2H2 (R2) 3LiH+3Al → 3LiAl + 3/2H2 (R3) The temperature of the first reaction is between 150-175°C, of the second between 180-220°C and the third between 400420°C. The first two reactions (R1 and R2) are very important from the hydrogen storage point of view: (i) both take place at a reasonable low temperatures and (ii) overall sum of theirs gravimetric hydrogen capacity is 7.8 wt.%, so the reactions (R1) and (R2) are accessible for practical hydrogen storage. However, the slow dehydrogenation kinetics and irreversibility under moderate condition hinder its imminent application. Particle refinement and catalyst or additive introduction by mechanical milling led to the significant improvement of LiAlH4 hydrogen storage properties [2]. However, during the milling process, the temperature in the milling chamber can significantly increase reaching the temperature of R1 or even R2 leading to the degradation of hydride, change in the hydrogen desorption mechanism (figure 1) and decrease in the hydrogen storage capacity of material [3]. So, in this work the impact of metallic (V, Mn an Cr) and metal oxide (Fe2O3 and Nb2O5) additives on the LiAlH4 hydrogen desorption properties with the emphasis on the hydride degradation process during milling and a consequent hydrogen desorption reaction mechanism was studied. The aim was to improve the hydrogen desorption kinetics without hydrogen capacity deterioration.6th International Symposium on Materials for Energy Storage and Conversion : July 5-8, Bol, island of Brač, Croatia, 2022

Temperature dependence of electric properties of GO and GO/WPA films on interdigital electrodes

In sensor devices the material of choice should be highly dependent on perturbation of environmental parameters. In order to achieve good sensitivity and selectivity of sensing devices to temperature, humidity or concentration of different gasses, the materials with adjustable properties are highly desirable. Electric properties of graphene oxide (GO) can be easily tuned by modification of surface chemistry and anchoring of functional compounds onto its two-dimensional structure. Prior to application of sensing device, research and development of materials system is the most essential step. In this work, the formation of GO and GO/12-tungstophosphoric acid (WPA) films with 6 wt.% of WPA on interdigital electrodes was investigated by variation of dip-coating parameters (receding angle and time between steps). Obtained films were thermally reduced in argon atmosphere after which optical microscopy was used to evaluate morphology and stability of deposited GO and GO/WPA films. Impedance spectroscopy was used to investigate the electric properties of the obtained films in range from 10 Hz to 100 kHz. Measured impedance values were correlated to the degree of material detachment and deposition parameters i.e. films showing the lowest impedance values had the smallest area of detached film. Additionally, impedance values were measured depending on the environment temperature which showed that GO/WPA films exhibit the lowest impedance values and good sensitivity to changes of temperature making it good a candidate for sensing devices.Twenty-First Young Researchers’ Conference - Materials Science and Engineering: Program and the Book of Abstracts; November 29 – December 1, 2023, Belgrade, Serbi

Investigating the influence of hydrothermal treatment on oxygen functional groups in graphene oxide-based nanocomposites

Different hierarchical ordering of nanomaterials, either as individual components or in the form of nanocomposites, is one of the approaches used for the development of supercapacitors. In this work, the effect of hydrothermal treatment on oxygen functional groups of nanocomposites between graphene oxide (GO), 12-tungstophosphoric acid (WPA), and 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) was examined. The mentioned materials were hydrothermally treated for 4, 8 and 12 hours at 180 °C in order to understand how interaction between the components is influencing development of surface chemistry. The results of Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy (Raman), and temperature-programmed desorption (TPD) are showing the surface and structural changes of GO (individually and in nanocomposite) as a result of hydrothermal treatment. Both FTIR and RAMAN confirm the presence of WPA and PTCDA. Additionally, it appears that hydrothermal treatment has no impact on the structural changes in PTCDA, which is consistent across various temperature conditions. TPD results indicate that prolonged hydrothermal treatment leads to a gradual increase of the number of functional groups of GO. However, the number of desorbed groups is influenced by the WPA and PTDCA components. This research offers new insights into GO, WPA, and PTCDA interactions which can have useful implications for development of electrochemical supercapacitors.Twenty-First Young Researchers’ Conference - Materials Science and Engineering: Program and the Book of Abstracts; November 29 – December 1, 2023, Belgrade, Serbi

Study of milling time impact on hydrogen desorption from LiAlH4-Fe2O3 composites

LiAlH4 was modified by mechanical milling and with the addition of 5 wt.% Fe2O3 in order to improve its hydrogen desorption properties. The composite was milled for 1, 3, 5, 7 or 15min, and depending on the milling time, various phenomena took place. Up to a milling time of 5min, the particle size of the composite decreases. Further milling leads to the particles agglomeration reaching the size of the starting material after 15min. Moreover, the mechanical milling process leads to the transformation of AlH - 4 to AlH 3 - 6 structure as a result of partial hydrogen desorption. Hydrogen desorption during the milling is the most pronounced in the sample milled for 15min, so this sample has only one hydrogen desorption peak in the temperature-programmed desorption measurements.Mechanical milling with the addition of Fe2O3 for up to 15min improves LiAlH4 hydrogen desorption properties as hydrogen desorption temperature and apparent activation energies decrease

Physicochemical properties of solvothermaly synthesized zinc copper ferrite nanoparticles

In the past two decades spinel ferrites nanoparticles have been extensively investigated due to their potential applications in a variety of fields (data storage, catalysis, energy, environment, biomedicine, etc.). In the present work, zinc ferrite nanoparticles with different copper content (Zn(1-x)CuxFe2O4; x=0, 0.2, 0.4, 0.6, and 0.8) but with the same particle size distribution and amount of oleic acid as capping agent were prepared by solvothermal synthesis and the physicochemical properties of as-prepared samples were investigated. The prepared samples were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR) and vibrating sample magnetometry (VSM). The XRD results show that all the diffraction maxima correspond to the cubic spinel structure, while TEM images reviled that samples are consisted of sphere-like particles, 5-7 nm in size. The presence of oleic acid on the surface of nanoparticles was confirmed by FTIR analysis. The magnetic measurements revealed superparamagnetic behavior of obtained powders, with gradual increase of saturation magnetization

Modification of MoS2/GO composites with ball milling and thermal treatment for catalytic application

Hydrogen production can be outlined as an important aspect of the modern economy. In order to be more clean and renewable, green hydrogen is most desirable, where expensive catalysts for water electrolysis are usually used. As alternative, transition metal dichalcogenides represent potentially good material, with room for further improvement. Molybdenum disulfide is a stable material with a reasonable amount of it available. The properties of the material can be easily tuned in order to increase its charge transport and create more active sites. The incorporation of defects and additives can be beneficial for the catalytic activity of MoS2. Graphene oxide (GO) is carbon nanomaterial, with a large surface area and when reduced, it could be used as a conductive additive. Furthermore, ball milling is a known low-cost, simple and scalable method to introduce defects in the structure. Therefore, combining these two approaches should result in a material with enhanced catalytic activity for hydrogen evolution reaction. The molybdenum disulfide was prepared by easy one-step hydrothermal synthesis. The graphene oxide was first obtained by modified Hummers’ method and after that reduced by thermal treatment at 200 °C. Thus prepared constituents are combined in different mass ratios and composites were obtained by milling with a high-energy ball mill. The various milling parameters were optimized. The prepared composites were analyzed as catalysts for hydrogen evolution reaction in an acidic solution

Electrochemical sensors based on pyrophyllite

V Conference of The Serbian Society for Ceramic Materials, 5CSCS-2019, June 11-13, 2019, Belgrade, Serbi

Sinteza i modifikacija naprednih nanomaterijala - pogled kroz prizmu obnovljivih izvora energije

Elektrohemijska istraživanja su prethodnih godina dala ključni podstrek globalnim stremljenjima ka obnovljivim izvorima energije. Višegeneracijski napori, u početku motivisani željom za fundamentalnim razumevanjem procesa, aktuelizovani su očekivanim nedostatkom fosilnih goriva i pratećim nepovoljnim uticajem na životnu sredinu. Nanomaterijali su omogućili spektakularan skok u tehnološkim inovacijama i neosporan je njihov doprinos obnovljivim izvorima energije. Zahvaljujući novim svojstvima nanomaterijala i njihovoj sinergiji, omogućeno je dalje unapređenje i integracija različitih funkcionalnosti. Pri tome, postalo je jasno da atomski precizan dizajn materijala postaje kritičan za razvoj naprava sledeće generacije. Ovo je posebno važno u slučaju nanokompozita gde interakcija komponenti pojačava moguće sinergijske doprinose. U izlaganju će biti dat osvrt na napredne metode sinteze i modifikacije materijala – od tradicionalnih, do tankih filmova, 0D i 2D nanomaterijala i njihovih kompozita – posmatranih kroz prizmu obnovljivih izvora energije i održivosti (elektrohemijski superkondenzatori, razgradnja vode, senzori, i dr.). Razvoj novih materijala i unapređenje elektrohemijskih sistema ima potencijal da suštinski učini obnovljivu energiju održivijom i dostupnijom, time otvarajući put ka održivoj budućnosti.Savremena stremljenja u elektrohemiji u proceu prelaska na obnovljive izvore energije: Naučni skup posvećen 100 - godišnjici rođenja inostranog člana SANU Dž. O'M. Bokrisa; 5. Jun, Beograd, 2023

Mechanochemical activation of LiAlH4-Fe2O3 composites-a method to enhance kinetics of hydrogen desorption

Mechanical milling of pure lithium alanate (LiAlH4) was done with addition of 5 weigh percent of Fe2O3 using different milling time ranging from 1 to 15 minutes [1]. Mechanical milling of composites causes destabilization of LiAlH4 structure as it observed by XRD measurements. Particle size distribution results reveals that composite particle size decrease with milling time up to 3 minutes, and then increase almost to the original size, for 15 min sample. Mechanical mailing cause phase transformation from AlH4- to AlH63-. As a consequence of structural and chemical changes, desorption properties of composites are change kinetic of desorption is improved in comparison to unmilled LiAlH4. The shifting of hydrogen desorption temperature to lower temperatures is observed together with change from multi-step desorption to one-step hydrogen desorption is also observed. This caused decrease in activation energy of composites from Ea = 665 kJ/mol for unmilled LiAlH4, Ea = 279 kJ/mol for 3 min milled composite.Solid-State Science & Research ; 10-11th June 2021, Onlin

Pyrophyllite modified carbon-based electrode

The main goal is to develop electrode material for the detection of traces of pesticides in food and water in a wide range of pH values. The leading idea is to use natural clay pyrophyllite to modify carbon paste electrode. SPEX Mixer/Mill 5100 is used for mechanochemical modification. The changes in the structure of pyrophyllite before and after the grinding process were studied by means of PSD, XRD, FTIR, and DTA-TG [1]. The electrochemical behavior of the sensor was followed using differential pulse stripping voltammetry (DPSV). It is shown that obtained material can be used as electrodes in electrochemical sensors for pesticide detection in a wide range of pH.Solid-State Science & Research Meeting : June 28-30, Zagreb, 2023