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1.
Describing protein conformations with Potts spins: Hamiltonian foundations of Zimm-Bragg model in water
Artem Badasyan, 2023, invited lecture at foreign university

Published: 07.02.2023; Views: 1; Downloads: 0
.pdf Fulltext (1,32 MB)

2.
Iron phosphide as an efficient electrocatalysts for hydrogen evolution
Saim Emin, Manel Machreki, Takwa Chouki, 2020, published scientific conference contribution abstract

Abstract: We report the solvothermal synthesis of iron phosphide electrocatalysts using a low-cost phosphorus precursor. The synthetic protocol allows for the preparation of a Fe2P phase at 300°C and FeP phase at 350°C. To enhance the catalytic activities of obtained iron phosphide particles, heat-treatments were carried out at elevated temperatures. Annealing at 500°C induced structural changes in the samples: (i) Fe2P provided a pure Fe3P phase (Fe3P−500°C) and (ii) FeP transformed into a mixture of iron phosphide phases (Fe2P/FeP−500°C). The electrocatalytic activities of heat-treated Fe2P−450°C, Fe3P−500°C, and Fe2P/FeP−500°C catalysts were studied for hydrogen evolution reaction (HER) in 0.5 M sulfuric acid (H2SO4). The lowest recorded overpotential of 110 mV at 10 mA cm−2 vs. a reversible hydrogen electrode was achieved with Fe2P/FeP−500°C catalyst. The present approach allows preparation of immobilized iron phsphide catalyst onto carbon support which is essential for application purpose. The procedure developed by us is an elegant approach to tune the composition of iron phosphide catalyst and control the morphology of particles
Keywords: solvothermal synthesis iron phosphide electrocatalysis HER
Published: 06.02.2023; Views: 22; Downloads: 0
.pdf Fulltext (2,67 MB)

3.
Iron phosphides as efficient electrocatalyst for hydrogen evolution and energy conversion
Takwa Chouki, Saim Emin, 2021, published scientific conference contribution abstract

Abstract: Transition metal phosphides have been demonstrated as outstanding multifunctional catalysts in a broad range of energy conversion technologies. We developed a solvothermal synthesis approach for iron phosphide electrocatalystsusing a low-cost phosphorus precursor.The synthetic protocol allows for the preparation of a Fe2P phase at 300°C and FeP phase at 350°C. The obtained compounds were coated on conductive substrates to prepare catalysts thin films. Here, we exploited different phases of iron phosphide as counter electrodes (CEs) in dye-sensitized solar cells (DSSCs) with an I−/I3− based electrolyte [2]. The solar-to-current conversion efficiency of the solar cells assembled with the Fe2P material reached 3.96±0.06%,which is comparable to the device assembled with a platinum (Pt) CE. In addition to DSSC applications, the iron phosphides were used as electrocatalyst for H2 evolution (Fig. 1). To enhance the catalytic activities of obtained iron phosphide particles, heat-treatments were carried out at elevated temperatures.Annealing at 500°C induced structural changes in the samples: (i) Fe2P provided a pure Fe3P phase (Fe3P−500°C) and (ii) FeP transformed into a mixture of iron phosphide phases (Fe2P/FeP−500°C). The electrocatalytic activities for H2 evolution of heat-treated catalysts were studied in 0.5 M sulfuric acid (H2SO4). The HER activities of the iron phosphide catalyst were found to be phase dependent. The lowest recorded overpotential of 110 mV at 10 mA cm−2 vs. a reversible hydrogen electrode was achieved with Fe2P/FeP−500°C catalyst. The developed procedure is an elegant approach to tune the composition of iron phosphide catalyst and control the morphology of particles.
Keywords: Iron phosphides electrocatalyst hydrogen evolution energy conversion
Published: 06.02.2023; Views: 25; Downloads: 0
.pdf Fulltext (649,13 KB)
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4.
Electrocatalytic Hydrogen Evolution with Transition Metal Based Compounds
Manel Machreki, Takwa Chouki, Saim Emin, 2021, published scientific conference contribution abstract

Abstract: Electrocatalytic water splitting is one of the cleanest and sustainable way to generate hydrogen. Transition metal based electrocatalysts like iron phosphides (Fe2P, FeP), molybdenum diselenides (MoSe2), and tungsten carbides (W2C, WC) have unique advantages including competitive cost compared to platinum, controllable active sites, and electronic structures that could significantly enhance the hydrogen evolution reaction (HER). Here, we present a combination of approaches for preparing catalyst materials. As an elegant technique, colloidal synthesis was used to synthesize Mo and W nanoparticles. Combined with selenization and carbidation approaches at elevated temperature, it allowed to synthesize MoSe2, W2C, and WC thin films. The syntheses of Fe2P and FeP catalyst were achieved in one-stage using triphenylphosphine precursor. The obtained catalysts were applied in electrocatalytic HER studies.
Keywords: iron phosphides molybdenum diselenide tungtsen carbides electrocatalysis hydrogen evolution
Published: 06.02.2023; Views: 28; Downloads: 0
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5.
Growth of MoSe2 thin films and use in electrochemical hydrogen evolution
Saim Emin, Plamen Stefanov, Burhan can Aktarla, Borjana Donkova, Takwa Chouki, 2020, published scientific conference contribution abstract

Abstract: We present the chemical vapor deposition (CVD) approach to grow MoSe2 thin films using colloidal molybdenum nanoparticles (Mo NPs). The synthetic protocol of Mo NPs was achieved using a wet-chemical method. The obtained Mo NPs were spin-coated on graphite substrates and heat-treated in the presence of selenium vapors at several temperatures (≥750 °C). The electrocatalytic activities of heat-treated MoSe2 thin films were studied for hydrogen evolution reaction (HER) in 0.5 M sulfuric acid (H2SO4). The lowest recorded overpotential of 218 mV at 10 mA cm−2 vs. a reversible hydrogen electrode was achieved with MoSe2−800°C catalyst. In addition, electrochemical impedance spectroscopy (EIS) was performed to access the chargetransfer resistance of the MoSe2 films. The colloidal approach combined with CVD is a promising route to produce carbon supported MoSe2 electrocatalyst for HER.
Keywords: MoSe2 thin films CVD HER
Published: 06.02.2023; Views: 25; Downloads: 0
.pdf Fulltext (109,58 KB)

6.
Electroreduction of Nitrogen to Ammonia at Iron Catalytic Sites Generated at Interfaces Utilizing Iron Phosphides and Heme-Type Complexes
2022, original scientific article

Abstract: There has been growing interest in the development of durable, specific and reasonably efficient low-cost catalysts for nitrogen (N2) electroreduction reaction, or nitrogen fixation, particularly in aqueous solutions capable of producing ammonia under ambient, or near ambient, conditions. The successful electrocatalytic reduction of nitrogen (N2) and formation of NH3 in alkaline an medium has been reported here using the Fe3P phase of iron phosphide. Detection of in-situ formed product has been achieved by probing the electrooxidation of NH3 to nitrogen (N2) using the additional working electrode modified with Pt nanoparticles. On mechanistic grounds, the iron (Fe0) sites seem to be electrocatalytic active during the reduction of nitrogen. The iron sites can also be generated within the phtalocyanine ring binding metal ions through four inwardly projecting nitrogen centers. Furthermore, horseradish peroxidase metalloenzyme, in which a large alpha- helical protein binds heme as a redox cofactor, is capable of inducing electroduction of N2.
Keywords: Electroreduction of Nitrogen to Ammonia Iron Catalytic Sites Iron Phosphides
Published: 06.02.2023; Views: 16; Downloads: 0
.pdf Fulltext (712,59 KB)

7.
Efficient Iron Phosphide Catalyst as a Counter Electrode in Dye-Sensitized Solar Cells
Sammy W Verbruggen, Rajeshreddy Ninakanti, Saim Emin, Aycan Atli, Moussab Harb, Takwa Chouki, Abdullah Yildiz, 2021, original scientific article

Abstract: Developing an efficient material as a counter electrode (CE) with excellent catalytic activity, intrinsic stability, and low cost is essential for the commercial application of dye-sensitized solar cells (DSSCs). Transition metal phosphides have been demonstrated as outstanding multifunctional catalysts in a broad range of energy conversion technologies. Here, we exploited different phases of iron phosphide as CEs in DSSCs with an I–/I3–-based electrolyte. Solvothermal synthesis using a triphenylphosphine precursor as a phosphorus source allows to grow a Fe2P phase at 300 °C and a FeP phase at 350 °C. The obtained iron phosphide catalysts were coated on fluorine-doped tin oxide substrates and heat-treated at 450 °C under an inert gas atmosphere. The solar-to-current conversion efficiency of the solar cells assembled with the Fe2P material reached 3.96 ± 0.06%, which is comparable to the device assembled with a platinum (Pt) CE. DFT calculations support the experimental observations and explain the fundamental origin behind the improved performance of Fe2P compared to FeP. These results indicate that the Fe2P catalyst exhibits excellent performance along with desired stability to be deployed as an efficient Pt-free alternative in DSSCs.
Keywords: Iron phosphide, catalyst, counter electrode, dye-sensitized solar cell, solvothermal synthesis
Published: 06.02.2023; Views: 23; Downloads: 0
.pdf Fulltext (4,96 MB)

8.
Highly active iron phosphide catalysts for selective electrochemical nitrate reduction to ammonia
Saim Emin, Luis Miguel Azofra, Moussab Harb, Georgi Tyuliev, Pawel J. Kulesza, Iwona Rutkowska, Beata Rytelewska, Manel Machreki, Takwa Chouki, 2023, original scientific article

Abstract: The electrochemical reduction reaction of the nitrate ion (NO3−), a widespread water pollutant, to valuable ammonia (NH3) is a promising approach for environmental remediation and green energy conservation. The development of high-performance electrocatalysts to selectively reduce NO3− wastes into value-added NH3 will open up a different route of NO3− treatment, and impose both environmental and economic impacts on sustainable NH3 synthesis. Transition metal phosphides represent one of the most promising earth-abundant catalysts with impressive electrocatalytic activities. Herein, we report for the first time the electrocatalytic reduction of NO3− using different phases of iron phosphide. Particularly, FeP and Fe2P phases were successfully demonstrated as efficient catalysts for NH3 generation. Detection of the in-situ formed product was achieved using electrooxidation of NH3 to nitrogen (N2) on a Pt electrode. The Fe2P catalyst exhibits the highest Faradaic efficiency (96 %) for NH3 generation with a yield (0.25 mmol h−1 cm-−2 or 2.10 mg h−1 cm−2) at − 0.55 V vs. reversible hydrogen electrode (RHE). The recycling tests confirmed that Fe2P and FeP catalysts exhibit excellent stability during the NO3− reduction at − 0.37 V vs. RHE. To get relevant information about the reaction mechanisms and the fundamental origins behind the better performance of Fe2P, density functional theory (DFT) calculations were performed. These results indicate that the Fe2P phase exhibits excellent performance to be deployed as an efficient noble metal-free catalyst for NH3 generation.
Keywords: Iron phosphide, Electrocatalysts, Nitrates reduction Ammonia, DFT calculations
Published: 02.02.2023; Views: 70; Downloads: 0
.pdf Fulltext (7,95 MB)

9.
Pisma
2022

Keywords: pisma, korespondenca, digitalizacija, kulturna dediščina
Published: 27.01.2023; Views: 107; Downloads: 2
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10.
MINOT: Modeling the intracluster medium (non-)thermal content and observable prediction tools
Rémi Adam, Hazal Gosku, A. Leingärtner-Goth, Steffano Ettori, R. Gnatyk, B. Hnatyk, Moritz Hütten, Judit Pérez-Romero, Miguel Sánchez-Conde, Olga Sergijenko, original scientific article

Abstract: In the past decade, the observations of diffuse radio synchrotron emission toward galaxy clusters revealed cosmic-ray (CR) electrons and magnetic fields on megaparsec scales. However, their origin remains poorly understood to date, and several models have been discussed in the literature. CR protons are also expected to accumulate during the formation of clusters and probably contribute to the production of these high-energy electrons. In order to understand the physics of CRs in clusters, combining of observations at various wavelengths is particularly relevant. The exploitation of such data requires using a self-consistent approach including both the thermal and the nonthermal components, so that it is capable of predicting observables associated with the multiwavelength probes at play, in particular in the radio, millimeter, X-ray, and γ-ray bands. We develop and describe such a self-consistent modeling framework, called MINOT (modeling the intracluster medium (non-)thermal content and observable prediction tools) and make this tool available to the community. MINOT models the intracluster diffuse components of a cluster (thermal and nonthermal) as spherically symmetric. It therefore focuses on CRs associated with radio halos. The spectral properties of the cluster CRs are also modeled using various possible approaches. All the thermodynamic properties of a cluster can be computed self-consistently, and the particle physics interactions at play are processed using a framework based on the Naima software. The multiwavelength observables (spectra, profiles, flux, and images) are computed based on the relevant physical process, according to the cluster location (sky and redshift), and based on the sampling defined by the user. With a standard personal computer, the computing time for most cases is far shorter than one second and it can reach about one second for the most complex models. This makes MINOT suitable for instance for Monte Carlo analyses. We describe the implementation of MINOT and how to use it. We also discuss the different assumptions and approximations that are involved and provide various examples regarding the production of output products at different wavelengths. As an illustration, we model the clusters Abell 1795, Abell 2142, and Abell 2255 and compare the MINOT predictions to literature data. While MINOT was originally build to simulate and model data in the γ-ray band, it can be used to model the cluster thermal and nonthermal physical processes for a wide variety of datasets in the radio, millimeter, X-ray, and γ-ray bands, as well as the neutrino emission.
Keywords: galaxy clusters, intracluster medium, cosmic rays, radiation mechanisms, numerical methods
Published: 27.01.2023; Views: 104; Downloads: 0
.pdf Fulltext (1,67 MB)

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