Solvothermaly synthesized copper doped bismuth vanadate

Photoeletrochemical (PEC) water splitting is a promising method for clean energy production and different oxide materials have been explored to find the right solution. Among them, as one of the most promising photoanode materials, bismuth vanadate (BiVO4) has attracted a lot of attention due to the suitable band gap edge alignment, lowcost synthesis method and great visible light harvesting features. Nowdays, research related to the BiVO4 is mostly oriented towards repairing poor charge transfer properties which exist due to the high rate of electron–hole recombination. Metal doping is one of the strategies to improve these intrinsic drawbacks. Herein, we report physicochemical properties of solvothermaly sinthesized pristine BiVO4, 1%-, 2.5%- and 5%- Cu-doped BiVO4 powders at 180 ºC for 8 h. X-ray diffraction (XRD) study indicates that, depending on the degree of doping, material exists in monoclinic or tetragonal scheelite phase. Pure monoclinic phase was formed in a case of pristine, 1%- and 2.5%- Cu doped samples. After doping with 5 %, phase transition occurred and material showed tetragonal phase. Scanning electron microscopy (SEM) reveals that samples with monoclinic phase consists of worm-like and prismatic structures while tetragonal samples exhibited spherical shape. Furthermore, structure was examined with Raman and FTIR spectroscopy. The results were in accordance with diffraction study where band positions were well matched with phase composition. Optical properties were characterized with UV–Vis diffuse reflectance spectroscopy (DRS) and photoluminescence (PL) spectroscopy. Monoclinic samples showed band gap around 2.4 eV, while sample with tetragonal phase has band gap around 2.8 eV. PL showed that that monoclinic samples possess better recombination features than tetragonal ones. Photoelectrochemical measurements suggest that material is sensitive towards visible light and, after doping, improved its performance towards oxygen evolution reaction.8th Conference of Young Chemists of Serbia; 29th October, Belgrade, Serbi

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

Surface chemistry, thermal stability and structural properties of graphene oxide/12-tungstophosphoric acid nanocomposite

In recent years the nanocomposites of graphene oxide (GO) and different inorganic and organic compounds have shown great potential for charge storage applications. In present work we have investigated the influence of 12-tungstophosphoric acid (WPA) on surface chemistry of graphene oxide and thermal stability of nanocomposite. For this purpose nanocomposites with different mass ratios of GO and WPA were prepared. The thermal stability of nanocomposites was investigated by thermogravimetric and differential thermal analysis (TGA-DTA) while changes in surface chemistry of GO and structural properties of WPA were investigated by Fourier transform infrared spectroscopy (FTIR) and temperature programmed desorption (TPD) method. The TGA-DTA measurements of composites have shown that the major mass loss, due to carbon combustion, is shifted to higher temperatures (~500 °C vs. 380 °C of pure GO). Furthermore, when the amount of WPA is higher than 25 mass percent the nanocomposites start to act like individual components, which was also confirmed by FTIR analysis. The amount of surface oxygen groups, monitored by both TPD and FTIR methods, showed ˝V˝ shaped dependence from the quantity of WPA with minimum at about 12 mass percent of WPA. At the same time, the FTIR spectra revealed the structural changes of WPA, displayed as shifting and splitting of characteristic bands of Keggin anion structure

Study of the interaction between graphene oxide and 12-tungstophosphoric acid in their nanocomposite

The rich surface chemistry and large surface area of graphene oxide (GO) provide a platform for various functional materials that synergistically enhance charge storage properties of the composite. In present work we have investigated interaction between GO and 12- thungstophosphoric acid (WPA) in their nanocomposites as a function of different mass ratio of constituents. For this purpose, the Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectrometry (XPS), temperature programmed desorption method (TPD) and thermogravimetric/differential thermal analysis (TGA-DTA) methods were used. FTIR spectra have shown shifts and splitting of characteristic bands of WPA as a result of interactions with GO. Both XPS and TPD methods have shown an initial decrease of the total amount of surface oxygen groups of GO, with a minimum at around 10 wt.% of WPA, above which a restoration of the amount of surface oxygen groups was noticed. TGA-DTA analysis revealed an improved thermal stability of the material up to 25 wt.% of WPA; at higher loading of WPA the thermal properties of nanocomposite became alike to the ones of individual components. The obtained results suggest optimal conditions for preparation of GO-WPA nanocomposites for electrochemical charge storage applications

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

Hydrogen storage properties of MgH2-Ni system

The effect of pure Ni addition (5 wt.%) in MgH2 powder was investigated mechanochemically for short milling times (15, 30, and 45 min). Obtained MgH2-Ni system was characterized by XRD, SEM-EDS, PSD, DSC, and TPD. Compared to pure MgH2, uniform distribution of nickel reduces the temperature of H2 desorption by more than 100 °C. It is shown that influence of two important processes, grinding and catalysis, may be followed separately. We can conclude that the catalysis of H2 desorption by Ni particles on MgH2 matrix is the dominant effect for the investigated short milling times.Twenty-First Young Researchers’ Conference - Materials Science and Engineering: Program and the Book of Abstracts; November 29 – December 1, 2023, Belgrade, Serbi

Graphene oxide/12 tungstophosphoric acid nanocomposites – achieving favorable properties with ion beams for electrochemical supercapacitors

In recent years graphene oxide (GO)/12-tungstophosphoric acid (WPA) nanocomposites have demonstrated promising potential for electrochemical supercapacitors. However, to enhance their performance, it is necessary to modify the surface chemistry of GO to minimize the influence of basal plane oxygen groups, which hinder the material's conductivity. Additionally, some degree of structural modification of WPA is desired. In this regard, ion beam irradiation presents a promising method to simultaneously optimize surface chemistry of GO and structurally modify WPA. To accomplish this, ion beam irradiation is employed for modification of individual components as well as their nanocomposites with varying mass ratios. Different ion species, fluences and energies were utilized depending on the sample type, ranging from 10 keV C to 710 MeV Bi. Spectroscopy methods were employed to gain insight into the type and degree of structural modification in WPA. A direct correlation is observed between the parameters of the ion beams and the resulting structural changes. As the disordering increases, the structure transitions from partially modified to increased bond breaking, ultimately leading to reconnected bronze-like structures. By increasing the fluence, a gradual modification of the structure and surface chemistry of GO was possible. The effects of irradiation on GO and WPA are particularly pronounced in irradiated composites, where higher capacitance is measured

Ion-beam irradiated graphene oxide, 12-tungstophosphoric acid and their nanocomposites for electrochemical supercapacitors

Ion beam modification of materials is notable method for achieving their unique structural, electronic, and other physicochemical properties. In the case of graphene oxide (GO) such modification of structure and surface chemistry is known to yield properties interesting for electrochemical supercapacitors. The performance of GO supercapacitors can be additionally improved by incorporating components with attractive redox properties. In this work, the influence of ion beam irradiation on synergy of GO and 12-tungstophosphoric acid (WPA) in their nanocomposite was investigated. For that, both components and their composites with different mass ratios were irradiated using different ion species, fluences and energies (from 10 keV C to 710 MeV Bi). For the irradiated WPA, results showed clear correlation between ion beam parameters, degree of structural modification and electrochemical properties. With increasing structural modification, bond breaking is first induced giving higher catalytic activity toward HER. Further irradiation resulted in an increased interconnection of polytungstate species producing lower catalytic activity and lower lithiation capacity. Irradiated GO showed modified surface chemistry, with preferable reduction of alkoxy and epoxy groups, changes in morphology and electric properties due to increased number of defects with increasing fluence, synergic effect of ion beam irradiated GO and WPA resulted in higher capacitance of irradiated composites compared to GO presumably because of interaction of structurally modified WPA with defect sites on GO thus reducing electrolyte flow along ion tracks

Ion-beam irradiated graphene oxide, 12-tungstophosphoric acid and their nanocomposites for electrochemical supercapacitors

Ion beam modification of materials is notable method for achieving their unique structural, electronic, and other physicochemical properties. In the case of graphene oxide (GO) such modification of structure and surface chemistry is known to yield properties interesting for electrochemical supercapacitors. The performance of GO supercapacitors can be additionally improved by incorporating components with attractive redox properties. In this work, the influence of ion beam irradiation on synergy of GO and 12-tungstophosphoric acid (WPA) in their nanocomposite was investigated. For that, both components and their composites with different mass ratios were irradiated using different ion species, fluences and energies (from 10 keV C to 710 MeV Bi). For the irradiated WPA, results showed clear correlation between ion beam parameters, degree of structural modification and electrochemical properties. With increasing structural modification, bond breaking is first induced giving higher catalytic activity toward HER. Further irradiation resulted in an increased interconnection of polytungstate species producing lower catalytic activity and lower lithiation capacity. Irradiated GO showed modified surface chemistry, with preferable reduction of alkoxy and epoxy groups, changes in morphology and electric properties due to increased number of defects with increasing fluence, synergic effect of ion beam irradiated GO and WPA resulted in higher capacitance of irradiated composites compared to GO presumably because of interaction of structurally modified WPA with defect sites on GO thus reducing electrolyte flow along ion tracks