1. Photoelectrochemical conversion of biomass alcohols using in-situ Sn-doped ▫$\alpha-Fe_2O_3$▫ thin filmsManel Machreki, Artem Badasyan, Dušan Žigon, Georgi Tyuliev, Saim Emin, 2025, original scientific article Abstract: Transformation of biomass into value-added chemicals and fuels is considered an upcycling process that is beneficial to resource utilization. In this study, we used a photoelectrochemical (PEC) approach for selective oxidation of propane-1,2,3-triol to dihydroxyacetone (DHA) with high efficiency and selectivity (99%) using Sn-doped -Fe2O3 (Sn:-Fe2O3) thin films with intrinsic oxygen vacancies (OVs). DHA is an essential compound utilized in the cosmetic industry. In a similar manner, we conducted the first study of the PEC oxidation of 4-hydroxy-3-methoxybenzyl alcohol under visible light. A kinetic model has been formulated and solved to find the time-dependent generation of the products. Electrochemical impedance analyses and PEC experiments demonstrated a correlation between the concentration of molecules and the catalytic performance of Sn:-Fe2O3. Studies using scavengers indicate that the photogenerated holes (h+), singlet oxygen (1O2), hydroxyl radicals (•OH), and superoxide radicals (•O2–) play key roles in achieving high PEC activity. This work provided a new perspective on designing efficient PEC systems for biomass conversion into energy and value-added chemicals.
Keywords: Sn-doped alpha-Fe2O3, oxygen vacancies, photoelectrochemical oxidation, propane-1, 2, 3-triol, 4-hydroxy-3-methoxybenzyl alcohol
Published in RUNG: 08.01.2025; Views: 710; Downloads: 6
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3. Photoelectrochemical activation of peroxymonosulfate using Sn-doped ▫$α-Fe_2O_3$▫ thin film for degradation of anti-inflammatory pharmaceutical drugManel Machreki, Georgi Tyuliev, Dušan Žigon, Qian Guo, Takwa Chouki, Ana Belén Jorge Sobrido, Stoichko Dimitrov, Saim Emin, 2024, original scientific article Abstract: 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.
Keywords: Sn-doped Fe2O3, oxygen vacancies, photoelectrochemical degradation, 2-(4-isobutylphenyl)propanoic acid, peroxymonosulfate
Published in RUNG: 10.01.2024; Views: 2286; Downloads: 42
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4. Defective ▫$TiO_2$▫ nanotube arrays for efficient photoelectrochemical degradation of organic pollutantsManel Machreki, Takwa Chouki, Georgi Tyuliev, Dušan Žigon, Bunsho Ohtani, Alexandre Loukanov, Plamen Stefanov, Saim Emin, 2023, original scientific article Abstract: 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.
Keywords: TiO2, nanotube arrays, photoelectrochemical degradation, organic pollutants
Published in RUNG: 12.06.2023; Views: 2593; Downloads: 12
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5. Reduced TiO2 nanotube arrays for photoelectrochemical degradation of pharmaceuticalManel Machreki, Takwa Chouki, Georgi Tyuliev, Dušan Žigon, Bunsho Ohtani, Alexandre Loukanov, Plamen Stefanov, Saim Emin, 2022, published scientific conference contribution abstract Keywords: TiO2, nanotube arrays, photoelectrochemical degradation, pharmaceuticals
Published in RUNG: 10.02.2023; Views: 2483; Downloads: 0
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