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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: 33; Prenosov: 2
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A novel multi-functional thiophene-based organic cation as passivation, crystalline orientation, and organic spacer agent for low-dimensional 3D/1D perovskite solar cells
Ali Semerci, Ali Buyruk, Saim Emin, Rik Hooijer, Daniela Kovacheva, Peter Mayer, Manuel A. Reus, Dominic Blätte, Marcella Günther, Nicolai F. Hartmann, 2023, izvirni znanstveni članek

Opis: Recently, the mixed-dimensional (3D/2D or 3D/1D) perovskite solar cellsusing small organic spacers have attracted interest due to their outstandinglong-term stability. Here, a new type of thiophene-based organic cation2-(thiophene-2yl-)pyridine-1-ium iodide (ThPyI), which is used to fabricatemixed-dimensional 3D/1D perovskite solar cells, is presented. TheThPyI-based 1D perovskitoid is applied as a passivator on top of a 3D methylammonium lead iodide (MAPI) to fabricate surface-passivated 3D/1Dperovskite films or added alone into the 3D perovskite precursor to generatebulk-passivated 3D MAPI. The 1D perovskitoid acts as a passivating agent atthe grain boundaries of surface-passivated 3D/1D, which improves the powerconversion efficiency (PCE) of the solar cells. Grazing incidence wide-angleX-ray scattering (GIWAXS) studies confirm that ThPyI triggers the preferentialorientation of the bulk MAPI slabs, which is essential to enhance chargetransport. Champion bulk-passivated 3D and surface-passivated 3D/1Ddevices yield 14.10% and 19.60% PCE, respectively. The bulk-passivated 3Doffers favorable stability, with 84% PCE retained after 2000 h withoutencapsulation. This study brings a new perspective to the design of organicspacers having a different binding motif and a passivation strategy to mitigatethe impact of defects in hybrid 3D/1D perovskite solar cells.A. Semerci, A. Buyruk, R. Hooijer, P. Mayer, D. Blätte, M. Günther, T. Bein,T. AmeriDepartment of Chemistry and Center for NanoScience (CeNS)Ludwig-Maximilians-Universität MünchenButenandtstrasse 5–13 (E), 81377 Munich,,Ajdovšˇcina5270,SloveniaThe ORCID identification number(s) for the author(s) of this articlecan be found under© 2023 The Authors. Advanced Optical Materials published byWiley-VCH GmbH. This is an open access article under the terms of theCreative Commons Attribution-NonCommercial License, which permitsuse, distribution and reproduction in any medium, provided the originalwork is properly cited and is not used for commercial purposes.DOI: 10.1002/adom.2023002671. IntroductionDuring the last decade, 3D organic–inorganic halide perovskites (OIHPs) haveemerged as promising absorber materialsfor photovoltaic applications due to theirsuperior properties such as high absorp-tion coefficient, long diffusion length ofthe charge carriers, fast charge transport,and tunable bandgap. The 3D OIHPs havedemonstrated rapid increase in powerconversion efficiency (PCE) from 3.8% to25.2%.[1–9]On the other hand, their mod-erate intrinsic stability against moistureand heat still has been a concern with aview on possible commercialization.[10–14]Instability of the 3D methyl ammoniumlead iodide (MAPI) perovskite is assumedto be due to its crystalline structure. Ionicmigration is now well recognized to affectthe photovoltaic properties of perovskitesolar cells. Especially, the ionic migrationcauses the generation and displacement ofvacancies in perovskite materials. OIHPsare mixed ionic–electronic conductors withiodide ions as the majority of ionic carriers.D. KovachevaInstitute of General and Inorganic ChemistryBulgarian Academy of SciencesSofia 1113, BulgariaM. A. Reus, P. Müller-BuschbaumTUM School of Natural SciencesDepartment of PhysicsChair for Functional MaterialsTechnical University of MunichJames-Franck-Str. 1, 85748 Garching, GermanyN. F. HartmannAttocube systems AGNanoscale AnalyticsneaspecEglfinger Weg 2, 85540 Haar, GermanyS. Lotfi, J. P. HofmannSurface Science LaboratoryDepartment of Materials and Earth SciencesTechnical University of DarmstadtOtto-Berndt-Str. 3, 64287 Darmstadt, GermanyAdv. Optical Mater.2023,11, 23002672300267 (1 of 13)© 2023 The Authors. Advanced Optical Materials published by Wiley-VCH GmbH
Ključne besede: perovskites, solar cells, passivation
Objavljeno v RUNG: 04.12.2023; Ogledov: 38; Prenosov: 0
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Efficient electrochemical nitrogen fixation at iron phosphide (Fe2P) catalyst in alkaline medium
Beata Rytelewska, Anna Chmielnicka, Takwa Chouki, Magdalena Skunik-Nuckowka, Shaghayegh Naghdi, Dominik Eder, Aleksandra Michalowska, Tomasz Ratajczyk, Egon Pavlica, Saim Emin, Yongsheng Fu, Iwona A. Rutkowska, Pawel J. Kulesza, 2023, izvirni znanstveni članek

Opis: A catalytic system based on iron phosphide (Fe2P) has exhibited electrocatalytic activity toward N2-reduction reaction in alkaline medium (0.5 mol dm−3 NaOH). Based on voltammetric stripping-type electroanalytical measurements, Raman spectroscopic and spectrophotometric data, it can be stated that the Fe2P catalyst facilitates conversion of N2 to NH3, and the process is fairly selective with respect to the competing hydrogen evolution. A series of diagnostic electrocatalytic experiments (utilizing platinum nanoparticles and HKUST-1) have been proposed and performed to control purity of nitrogen gas and to probe presence of potential contaminants such as ammonia, nitrogen oxo-species and oxygen. On the whole, the results are consistent with the view that the interfacial reduced-iron (Fe0) centers, while existing within the network of P sites, induce activation and reduction of nitrogen, parallel to the water splitting (reduction) to hydrogen. It is apparent from Tafel plots and impedance measurements that mechanism and dynamics of nitrogen reduction depends on the applied electroreduction potential. The catalytic system exhibits certain tolerance with respect to the competitive hydrogen evolution and gives (during electrolysis at -0.4 V vs. RHE) the Faradaic efficiency, namely, the selectivity (molar) efficiency, toward production of NH3 on the level of 60%. Under such conditions, the NH3-yield rate has been found to be equal to 7.5 µmol cm−2 h−1 (21 µmol m−2 s−1). By referring to classic concepts of electrochemical kinetic analysis, the rate constant in heterogeneous units has been found to be on the moderate level of 1-2*10−4 cm s−1 (at -0.4 V). The above mentioned iron-phosphorous active sites, which are generated on surfaces of Fe2P particles, have also been demonstrated to exhibit strong catalytic properties during reductions of other electrochemically inert reactants, such as oxygen, nitrites and nitrates.
Ključne besede: Nitrogen reduction, Alkaline medium, Iron phosphide catalyst, Ammonia, Electrochemical determinations
Objavljeno v RUNG: 30.11.2023; Ogledov: 116; Prenosov: 0
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Defective TiO2 Nanotube Arrays for Efficient PhotoelectrochemicalDegradation 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, PhotoelectrochemicalDegradation of Organic Pollutants
Objavljeno v RUNG: 12.06.2023; Ogledov: 608; Prenosov: 3
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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: 745; Prenosov: 0
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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: 662; Prenosov: 0
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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: 724; Prenosov: 0
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