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1.
Photoelectrochemical activation of peroxymonosulfate using Sn-doped ▫$α-Fe_2O_3$▫ thin film for degradation of anti-inflammatory pharmaceutical drug
Manel Machreki, Georgi Tyuliev, Dušan Žigon, Qian Guo, Takwa Chouki, Ana Belén Jorge Sobrido, Stoichko Dimitrov, Saim Emin, 2024, izvirni znanstveni članek

Opis: Introduction of oxygen vacancies (OVs) has been investigated as a promising way to improve the electrical and catalytic characteristics of a hematite (α-Fe2O3) based photoelectrode. In this work, we develop a novel method for preparing porous Sn-doped α-Fe2O3 (Sn:Fe2O3) thin films with intrinsic OVs. The procedure included spin- coating an iron precursor onto a fluorine-doped tin oxide (FTO) substrate, followed by thermal treatment at elevated temperatures. The influence of Sn dopant on the optoelectronic properties of α-Fe2O3 was demonstrated by X-ray photoelectron spectroscopy and photoelectrochemical (PEC) measurements. The combined effect of OVs and Sn doping was found to play a synergistic role in reducing the charge recombination’s. The Sn:Fe2O3 photoanodes were used as a dual catalyst to oxidise water and break down an anti-inflammatory drug called 2-(4- isobutylphenyl)propanoic acid (IBPA). The Sn:Fe2O3 thin film with a 30-minute heat treatment time displayed the highest incident photon-to-current efficiency. For the first time, Sn:Fe2O3 thin films were utilised in the effective PEC degradation of IBPA employing peroxymonosulfate (PMS) under visible light illumination. The hydroxyl radicals (•OH), singlet oxygen (1O2), photogenerated holes (h+), and sulfate radicals (SO4 • ) were discovered to be the main reactive species during PEC degradation. IBPA degradation and the formation of new compounds were verified using liquid chromatography-mass spectrometry. The Lepidium sativum L phytotoxicity test reveals that PEC-treated wastewater with IBPA exhibits decreased toxicity.
Ključne besede: Sn-doped Fe2O3, oxygen vacancies, photoelectrochemical degradation, 2-(4-isobutylphenyl)propanoic acid, peroxymonosulfate
Objavljeno v RUNG: 10.01.2024; Ogledov: 834; Prenosov: 41
.pdf Celotno besedilo (2,44 MB)
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2.
Materials for sustainable electrochemical energy conversion
Saim Emin, Takwa Chouki, Manel Machreki, 2023, objavljeni povzetek znanstvenega prispevka na konferenci (vabljeno predavanje)

Opis: The process of hydrogen evolution reaction (HER) through water electrolysis is an important technology for establishing the so called "hydrogen economy". Here we will cover different systems for electrocatalytic HER. Transition metal carbides and metal phosphides are alternative to platinum (Pt) and offer excellent electrocatalytic activity for HER. Pyrolysis of hexacarbonyl tungsten, W(CO)6, in 1-octadecene has been used to prepare colloidal tungsten, W, nanoparticles (NPs) [1]. The obtained W NPs has been spin-coated on graphite (C) electrodes. Heat treatment of the W/C electrodes at elevated temperatures (≥ 900°C) allows the preparation of metallic W and tungsten carbide (W2C@WC) thin films. The obtained W2C@WC electrodes were used for hydrogen evolution studies (HER) in 0.5M H2SO4. Cyclic voltammetry tests for 1000 cycles showed that W2C@WC exhibit long term stability without significant drop in current density. The overpotential defined at 10 mA/cm2 is 310 mV vs. RHE giving an excellent catalytic activity for HER. Iron phosphide electrocatalysts were synthesized using a triphenylphosphine (TPP) precursor. Different iron phosphide phases were synthesized at 300°C (Fe2P) and at 350°C ( FeP ) [2]. To enhance the catalytic activities of obtained iron phosphide particles heat-treatments were carried out at elevated temperatures. Annealing at 500°C under reductive atmosphere 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 lowest electrode potential of 110 mV vs. a reversible hydrogen electrode (RHE) at 10 mA cm−2 was achieved with Fe2P/FeP−500°C catalyst
Ključne besede: Fe2P, electrocatalysis, hydrogen, ammonia
Objavljeno v RUNG: 13.12.2023; Ogledov: 919; Prenosov: 3
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3.
The role of lattice defects on the optical properties of TiO[sub]2 nanotube arrays for synergistic water splitting
Manel Machreki, Takwa Chouki, Georgi Tyuliev, Mattia Fanetti, Matjaž Valant, Denis Arčon, Matej Pregelj, Saim Emin, 2023, izvirni znanstveni članek

Opis: In this study, we report a facile one-step chemical method to synthesize reduced titanium dioxide (TiO2) nanotube arrays (NTAs) with point defects. Treatment with NaBH4 introduces oxygen vacancies (OVs) in the TiO2 lattice. Chemical analysis and optical studies indicate that the OV density can be significantly increased by changing reduction time treatment, leading to higher optical transmission of the TiO2 NTAs and retarded carrier recombination in the photoelectrochemical process. A cathodoluminescence (CL) study of reduced TiO2 (TiO2–x) NTAs revealed that OVs contribute significantly to the emission bands in the visible range. It was found that the TiO2 NTAs reduced for a longer duration exhibited a higher concentration of OVs. A typical CL spectrum of TiO2 was deconvoluted to four Gaussian components, assigned to F, F+, and Ti3+ centers.
Ključne besede: TiO2 nanotubes, defects, cathodoluminescence
Objavljeno v RUNG: 13.12.2023; Ogledov: 656; Prenosov: 7
.pdf Celotno besedilo (5,75 MB)
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4.
Tuning the activity of iron phosphide electrocatalysts for sustainable energy conversion
Saim Emin, Takwa Chouki, Manel Machreki, 2023, objavljeni povzetek znanstvenega prispevka na konferenci (vabljeno predavanje)

Opis: Electrocatalysis is a promising approach for the sustainable conversion of renewable energy sources, such as solar and wind power, into chemical energy that can be stored and used on demand. By harnessing renewable electricity to drive electrochemical reactions, we can produce fuels and chemicals in a way that is both clean and cost-effective. As we continue to develop new electrocatalytic materials and improve the efficiency of existing processes, the potential for electrocatalysis to transform our energy system will only continue to grow. We report the use of iron phosphide (Fe2P, FeP) in several electrocatalytic applications, such as reduction of nitrate ions (NO3), hydrogen and oxygen evolution studies. The electrochemical reduction of the nitrate ion (NO3), a widespread water pollutant, to valuable ammonia (NH3) is a promising approach to achieving green energy conservation. Particularly, FeP and Fe2P phases were successfully demonstrated as efficient catalysts for NH3 generation. Detection of the in-situ formed product using a bi-potentiostat was achieved by 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). 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.
Ključne besede: Fe2P, FeP, electrocatalysis, NH3 reduction, counter electrode
Objavljeno v RUNG: 04.12.2023; Ogledov: 834; Prenosov: 4
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5.
Defective ▫$TiO_2$▫ nanotube arrays for efficient photoelectrochemical degradation of organic pollutants
Manel Machreki, Takwa Chouki, Georgi Tyuliev, Dušan Žigon, Bunsho Ohtani, Alexandre Loukanov, Plamen Stefanov, Saim Emin, 2023, izvirni znanstveni članek

Opis: Oxygen vacancies (OVs) are one of the most critical factors that enhance the electrical and catalytic characteristics of metal oxide-based photo-electrodes. In this work, a simple procedure was applied to prepare reduced TiO 2 nanotube arrays (NTAs) (TiO 2−x) via a one-step reduction method using NaBH 4. A series of characterization techniques were used to study the structural, optical, and electronic properties of TiO 2−x NTAs. X-ray photoelectron spectroscopy confirmed the presence of defects in TiO 2−x NTAs. Photoacoustic measurements were used to estimate the electron-trap density in the NTAs. Photoelectrochemical studies show that the photocurrent density of TiO 2−x NTAs was nearly 3 times higher than that of pristine TiO 2. It was found that increasing OVs in TiO 2 affects the surface recombination centers, enhances electrical conductivity, and improves charge transport. For the first time, a TiO 2−x photoanode was used in the photo-electrochemical (PEC) degradation of a textile dye (basic blue 41, B41) and ibuprofen (IBF) pharmaceutical using in situ generated reactive chlorine species (RCS). Liquid chromatography coupled with mass spectrometry was used to study the mechanisms for the degradation of B41 and IBF. Phytotoxicity tests of B41 and IBF solutions were performed using Lepidium sativum L. to evaluate the potential acute toxicity before and after the PEC treatment. The present work provides efficient PEC degradation of the B41 dye and IBF in the presence of RCS without generating harmful products.
Ključne besede: TiO2, nanotube arrays, photoelectrochemical degradation, organic pollutants
Objavljeno v RUNG: 12.06.2023; Ogledov: 1262; Prenosov: 7
.pdf Celotno besedilo (4,22 MB)
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6.
7.
Colloidal nanoparticles for photo(electro)catalytic water splitting studies
Saim Emin, Manel Machreki, Takwa Chouki, 2022, objavljeni povzetek znanstvenega prispevka na konferenci

Ključne besede: nanoparticles, electrocatalysis, water splitting
Objavljeno v RUNG: 10.02.2023; Ogledov: 1579; Prenosov: 0
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8.
9.
Reduced TiO2 nanotube arrays for photoelectrochemical degradation of pharmaceutical
Manel Machreki, Takwa Chouki, Georgi Tyuliev, Dušan Žigon, Bunsho Ohtani, Alexandre Loukanov, Plamen Stefanov, Saim Emin, 2022, objavljeni povzetek znanstvenega prispevka na konferenci

Ključne besede: TiO2, nanotube arrays, photoelectrochemical degradation, pharmaceuticals
Objavljeno v RUNG: 10.02.2023; Ogledov: 1261; Prenosov: 0
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10.
Iron phosphide as an efficient electrocatalysts for hydrogen evolution : abstract
Takwa Chouki, Manel Machreki, Saim Emin, 2020, objavljeni povzetek znanstvenega prispevka na konferenci

Opis: 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
Ključne besede: solvothermal synthesis iron phosphide electrocatalysis HER
Objavljeno v RUNG: 06.02.2023; Ogledov: 1332; Prenosov: 0
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