Researcher:
Sadeghi, Ebrahim

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PhD Student

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Ebrahim

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Sadeghi

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Sadeghi, Ebrahim

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Now showing 1 - 9 of 9
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    Publication
    Metal-substituted zirconium diboride (Zr= Ni, Co, and Fe) as low-cost and high-performance bifunctional electrocatalyst for water splitting
    (Elsevier, 2021) N/A; N/A; N/A; N/A; Department of Chemistry; Department of Chemistry; Mete, Büşra; Peighambardoust, Naeimeh Sadat; Aydın, Samet; Sadeghi, Ebrahim; Aydemir, Umut; Master Student; Researcher; Other; PhD Student; Faculty Member; Koç University Boron and Advanced Materials Application and Research Center (KUBAM) / Koç Üniversitesi Bor ve İleri Malzemeler Uygulama ve Araştırma Merkezi (KUBAM); Graduate School of Sciences and Engineering; N/A; N/A; Graduate School of Sciences and Engineering; College of Sciences; N/A; N/A; N/A; 58403
    Recent years have witnessed an unprecedented surge in research on earth-abundant and efficient electrocatalysts for the water splitting process. Among those, the development of boron-based advanced catalysts is subject to designing the active and durable compounds, working as bifunctional materials under alkaline medium. In this study, a series of ZrB2-based catalysts with a general formula of Zr(1-x)TMxB2 (x = 0.05, 0.1, and 0.2) (TM = Fe, Co, and Ni) were prepared through a straightforward route and employed as bifunctional electrocatalysts in hydrogen and oxygen evolution reactions (HER and OER). The electrochemical measurements confirmed that the incorporation of Ni into the crystal structure of ZrB2 in the Zr0.8Ni0.2B2 sample led to an onset potential of 1.58 V in OER at a current density of 10 mA cm(-2), indicating a remarkable performance with a very low overpotential of 350 mV. Besides, Zr0.8Ni0.2B2 displayed an infinitesimal value of 56.6 mV dec(-1) regarding the Tafel slope, which was lesser as compared to the commercial RuO2 (66.2 mV dec(-1)). For the case of HER, Zr0.8Co0.2B2 showed the best performance compared to other samples with an overpotential of 420 mV and a Tafel slope of 101.6 mV dec(-1), following the Volmer mechanism. Both catalysts were examined for their long-term stability, manifesting excellent catalytic durability even after 12 h. Surprisingly, Zr0.8Co0.2B2 exhibited a drop from 420 to 380 mV in the overpotential value after 1000 CV sweeps, providing a promising performance in terms of HER. As-prepared metal-substituted ZrB2 electrocatalysts have great potential to be implemented in various green energy system applications. (C) 2021 Elsevier Ltd. All rights reserved.
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    Design of metal-substituted tungsten diboride as an efficient bifunctional electrocatalyst for hydrogen and oxygen evolution
    (Wiley, 2022) N/A; N/A; N/A; N/A; Department of Chemistry; Department of Chemistry; Hatipoğlu, Ezgi; Peighambardoust, Naeimeh Sadat; Sadeghi, Ebrahim; Aydemir, Umut; Master Student; Researcher; PhD Student; Faculty Member; Koç University Boron and Advanced Materials Application and Research Center (KUBAM) / Koç Üniversitesi Bor ve İleri Malzemeler Uygulama ve Araştırma Merkezi (KUBAM); Graduate School of Sciences and Engineering; N/A; Graduate School of Sciences and Engineering; College of Sciences; N/A; N/A; N/A; 58403
    Transition metal diborides (TMDbs) have recently attracted the scientific community's attention because of their remarkable attributes as bifunctional catalysts for both oxygen and hydrogen evolution reactions (OER/HER). Herein, we present the electrocatalytic OER/HER of Co- and Ni-incorporated WB2 (W(1-x)TMxB2: TM = Ni and Co; x = 0, 0.1, 0.2, and 0.3) under alkaline media. Metal-substituted WB2 was constructed with two different synthetic approaches, molten salt (ms) and carbothermal (ct) reduction, to explore the influence of morphology on electrochemical properties to drive OER/HER in 1 M KOH. In general, materials synthesized by the ms technique are relatively better catalysts toward OER/HER. Among the samples, W0.8Co0.2B2/ms demanded the lowest respective overpotential of 340 and 363 mV to generate the current density of 10 mA cm(-2) for OER/HER and exhibited favorable stability at 10 mA cm(-2) for 12 h which were ascribed to high double-layer capacitance (0.247 mF cm(-2)) and low charge-transfer resistance.
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    PublicationOpen Access
    Designing in situ grown ternary oxide/2D Ni-BDC MOF nanocomposites on Nickel foam as efficient electrocatalysts for electrochemical water splitting
    (American Chemical Society, 2022) Department of Chemistry; N/A; N/A; N/A; Department of Chemistry; Aydemir, Umut; Peighambardoust, Naeimeh Sadat; Sadeghi, Ebrahim; Chamani, Sanaz; Faculty Member; Researcher; PhD Student; Researcher; N/A; Koç University Boron and Advanced Materials Application and Research Center (KUBAM) / Koç Üniversitesi Bor ve İleri Malzemeler Uygulama ve Araştırma Merkezi (KUBAM); N/A; N/A; College of Sciences; N/A; Graduate School of Sciences and Engineering; N/A; 58403; N/A; N/A; N/A
    The security of future energy, hydrogen, is subject to designing high-performance, stable, and low-cost electrocatalysts for hydrogen and oxygen evolution reactions (HERs and OERs), for the realization of efficient overall water splitting. Two-dimensional (2D) metal-organic frameworks (MOFs) introduce a large family of materials with versatile chemical and structural features for a variety of applications, such as supercapacitors, gas storage, and water splitting. Herein, a series of nanocomposites based on NCM/Ni-BDC@NF (N-Ni, C-Co, M:F-Fe, C-Cu, and Z-Zn, BDC: benzene dicarboxylic acid, NF: nickel foam) were directly developed on NF using a facile yet scalable solvothermal method. After coupling, the electronic structure of metallic atoms was well-modulated. Based on the XPS results, for the NCF/Ni-BDC, cationic atoms shifted to higher oxidation states, favorable for the OER. Conversely, for the NCZ/Ni-BDC and NCC/Ni-BDC nanocomposites, cationic atoms shifted to lower oxidation states, advantageous for the HER. The as-prepared NCF/Ni-BDC demonstrated prominent OER performance, requiring only 1.35 and 1.68 V versus a reversible hydrogen electrode to afford 10 and 50 mA cm-2 current densities, respectively. On the cathodic side, NCZ/Ni-BDC exhibited the best HER activity with an overpotential of 170 and 350 mV to generate 10 and 50 mA cm-2, respectively, under 1.0 M KOH medium. In a two-electrode alkaline electrolyzer, the assembled NCZ/Ni-BDC (cathode) ∥ NCF/Ni-BDC (anode) couple demanded a cell voltage of only 1.58 V to produce 10 mA cm-2. The stability of NCF/Ni-BDC toward OER was also exemplary, experiencing a continuous operation at 10, 20, and 50 mA cm-2 for nearly 45 h. Surprisingly, the overpotential after OER stability at 50 mA cm-2 dropped drastically from 450 to 200 mV. Finally, the faradaic efficiencies for the overall water splitting revealed the respective values of 100 and 85% for the H2 and O2 production at a constant current density of 20 mA cm-2.
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    Facile synthesis of graphene quantum dots/ZSM-5 type metalosilicate composites and evaluating their performance in photocatalytic degradation of methylene blue and electrochemical water splitting
    (Elsevier B.V., 2023) Mokhtari, Azam; Yavari, Azin; Khatamian, Maasoumeh; N/A; N/A; Department of Chemistry; Department of Chemistry; Sadeghi, Ebrahim; Peighambardoust, Naeimeh Sadat; Aydemir, Umut; PhD Student; Researcher; Faculty Member; Koç University Boron and Advanced Materials Application and Research Center (KUBAM) / Koç Üniversitesi Bor ve İleri Malzemeler Uygulama ve Araştırma Merkezi (KUBAM); Graduate School of Sciences and Engineering; N/A; College of Sciences; N/A; N/A; 58403
    Graphene quantum dots (GQDs)/ZSM-5 type cobaltosilicate and GQDs/ZSM-5 type chromosilicate composites were prepared by two methods; direct and solid state dispersion (SSD) method. The composites were characterized using XRD, FT-IR, UV–vis absorption, and SEM techniques. The photocatalytic activities of composites were evaluated by degradation of methylene blue (MB) under both UV and vis light irradiation. The composites prepared by direct method showed better photocatalytic activity and the GQDs/chromosilicate composite had a superior performance. This composite could remove about 96 % and 87 % of MB at first 30 min under UV and vis light, respectively. The results of photocatalytic degradation kinetic studies revealed that the composites follow the pseudo-second-order kinetic model (R2 = 0.99) with rate constants ranging from 0.295 to 0.581 g mg−1 min−1 for different composites prepared by direct method. The GQDs/metalosilicate composites were also examined for the electrochemical water splitting. The GQDs/cobaltosilicate composites required lower overpotentials for HER and OER in comparison to the pure GDQs and cobaltosilicate. Moreover, the charge transfer resistance and Warburg impedance was lower than the corresponding values obtained for the pure cobaltosilicate and GQDs. These new GQDs-based composites are expected to open new windows in materials science and electrocatalytic-related processes.
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    Evaluating electrocatalytic activity of metal-substituted hafnium diboride (Hf1-xtmxb2; TM = Ni and Co) toward water splitting
    (Elsevier Science Sa, 2022) N/A; N/A; N/A; N/A; N/A; Department of Chemistry; Department of Chemistry; Peighambardoust, Naeimeh Sadat; Sadeghi, Ebrahim; Mete, Büşra; Yağcı, Mustafa Barış; Aydemir, Umut; Researcher; PhD Student; Master Student; Researcher; Faculty Member; Koç University Boron and Advanced Materials Application and Research Center (KUBAM) / Koç Üniversitesi Bor ve İleri Malzemeler Uygulama ve Araştırma Merkezi (KUBAM); Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); N/A; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; N/A; College of Sciences; N/A; N/A; N/A; N/A; 58403
    Developing non-precious, competent, and environmentally benign electrocatalysts to efficiently drive water electrolysis is critical but at the same time demanding. Layered metal diborides (MDbs) holding attractive features mainly due to the presence of borophene subunits in its crystal structure have lately sparked a great deal of attention for electrocatalytic applications. Here, we highlight the synthesis and electrocatalytic properties of HfB2-based electrocatalysts as Hf1-xTMxB2 (TM = Ni and Co; x = 0.1, 0.2, and 0.3) for both hydrogen and oxygen evolution reactions (HER/OER) under 1 M KOH. Amidst as-prepared samples, Hf0.8Ni0.2B2 and Hf0.8Co0.2B2 appeared to be the best OER and HER catalysts, generating the current density of 10 mA cm(-2) at overpotentials of 320 and 430 mV, individually. Concerning the OER, Hf0.8Ni0.2B2 performed an oxygen-evolving process similar to benchmarking RuO2 (an overpotential of 290 mV at 10 mA cm(-2)) and even more facile kinetics compared to RuO2 with Tafel slopes of 39.5 mV dec(-1) vs. 66.2 mV dec(-1). In addition, regarding HER, Hf0.8Co0.2B2 displayed an enhanced performance relative to pristine HfB2 (an overpotential of 620 mV at 10 mA cm(-2)), still inferior to noble metal 10% Pt/C (an overpotential of 198 mV at 10 mA cm(-2)). Furthermore, the interpretation of Tafel slopes unveils that all samples follow the Volmer path as HER mechanism. Finally, both best-performing electrocatalysts tolerated the current density of 10 mA cm(-2) for 20 h, manifesting stable bifunctional catalysts.
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    Photocatalytic hydrogen evolution performance of metal ferrites/polypyrrole nanocomposites
    (Pergamon-Elsevier Science Ltd, 2022) Chamani, Sanaz; Doğanay, Fatmanur; Yanalak, Gizem; Aslan, Emre; Asghari, Elnaz; Patir, İmren Hatay; Khatamian, Maasoumeh; N/A; N/A; N/A; Department of Chemistry; Department of Chemistry; Department of Chemistry; Sadeghi, Ebrahim; Peighambardoust, Naeimeh Sadat; Eroğlu, Zafer; Metin, Önder; Aydemir, Umut; PhD Student; Researcher; Researcher; Faculty Member; Faculty Member; Koç University Boron and Advanced Materials Application and Research Center (KUBAM) / Koç Üniversitesi Bor ve İleri Malzemeler Uygulama ve Araştırma Merkezi (KUBAM); Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); Graduate School of Sciences and Engineering; N/A; N/A; College of Sciences; College of Sciences; N/A; N/A; N/A; 46962; 58403
    The combination of inorganic (e.g., ferrite nanoparticles) and organic (e.g., conducting polymers) materials in the fabrication of heterojunctions or composites is an attractive scheme in the field of photocatalysis. We took the advantage of this phenomenon by fabricating MFerrite (M = Co, Ni, and Zn) @polypyrrole (MFerrite@Ppy) nanocomposites with a varying weight percentage of Ppy for the hydrogen production through photo -catalytic water splitting under visible light irradiation. The structural, spectral, morpho-logical, compositional, and optical features of the as-prepared nanocomposites were analyzed in full depth. The average crystallite sizes were estimated to be 30-40 nm from the XRD patterns which were further validated by TEM images from which a core-shell structure of the composites can be inferred. Likewise, the SEM images revealed spherical Ppy particles with a diameter in the range of 100-300 nm. From a photocatalytic viewpoint, CoFerrite@30Ppy is endowed with some peculiar characteristics including but not limited to strong light-harvesting ability (ranging between 300 and 650 nm), narrow optical band gap (as low as 1.6 eV), and higher photoluminescence (PL) lifetime (6.41 ns) which justify why it stands out among all composites in terms of photocatalysis. Under 8 h illumination of simulated visible light and using triethanolamine (TEOA) as a hole scavenger and Eosin -Y (EY) as a dye sensitizer, the photocatalytic hydrogen evolution (HER) amount for CoFerrite@30Ppy was found to be 10.44 mmol g-1, far greater than any other composite catalysts in this study. From the PL spectra, it can be pointed out that sensitization of CoFerrite with 30 wt % Ppy conduces to simultaneous deceleration of the electron-hole recombination process and acceleration of the transference of excitons within the system.
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    Tailoring the morphology of cost-effective vanadium diboride through cobalt substitution for highly efficient alkaline water oxidation
    (American Chemical Society (ACS), 2021) N/A; N/A; Department of Chemistry; Department of Chemistry; Sadeghi, Ebrahim; Peighambardoust, Naeimeh Sadat; Aydemir, Umut; PhD Student; Researcher; Faculty Member; Koç University Boron and Advanced Materials Application and Research Center (KUBAM) / Koç Üniversitesi Bor ve İleri Malzemeler Uygulama ve Araştırma Merkezi (KUBAM); Graduate School of Sciences and Engineering, N/A; College of Sciences; N/A; N/A; 58403
    Design and development of efficient, economical, and durable electrocatalysts for oxygen evolution reaction (OER) are of key importance for the realization of electrocatalytic water splitting. To date, VB 2 and its derivatives have not been considered as electrocatalysts for water oxidation. Herein, we developed a series of electrocatalysts with a formal composition of V1-xCoxB2 (x = 0, 0.05, 0.1, and 0.2) and employed them in an oxygen-evolving reaction. The incorporation of Co into the VB2 structure caused a dramatic transformation in the morphology, resulting in a super low overpotential of 200 mV at 10 mA cm(-2) for V0.9Co0.1B2 and displaying much greater performance compared to the noble-metal catalyst RuO2 (290 mV). The longevity of the best-performing sample was assessed through the exposure to the current density of 10 mA cm(-2), showing relative durability after 12 h under 1 M KOH conditions. The Faradaic efficiency tests corroborated the initiation of OER at 1.45 V (vs RHE) and suggested a potential region of 1.50-1.55 V (vs RHE) as the practical OER region. The facile electron transfer between metal(s)metalloid, high specific surface area, and availability of active oxy-hydroxy species on the surface were identified as the major contributors to this superior OER performance.
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    PublicationOpen Access
    Lead halide perovskite quantum dots for photovoltaics and photocatalysis: a review
    (American Chemical Society (ACS), 2022) Department of Chemistry; Department of Chemistry; Peighambardoust, Naeimeh Sadat; Sadeghi, Ebrahim; Aydemir, Umut; Researcher; PhD Student; Faculty Member; Koç University AKKİM Boron-Based Materials _ High-technology Chemicals Research _ Application Center (KABAM) / Koç Üniversitesi AKKİM Bor Tabanlı Malzemeler ve İleri Teknoloji Kimyasallar Uygulama ve Araştırma Merkezi (KABAM); College of Sciences; Graduate School of Sciences and Engineering; N/A; N/A; 58403
    Lead halide-based perovskite quantum dots (PQDs) have recently emerged as an important class of nanocrystal (NC) materials for optoelectronic and photoelec-trochemical applications. Thanks to their intriguing features including tunable band gap, narrow emission, high charge carrier mobility, remarkable light-absorbing factors, and long charge diffusion length, there has been a surge in research on lead halide-based PQDs and their applications. In this review, we showcase the fundamentals of PQDs and two principal applications including PQD solar cells (PQDSCs) and photocatalytic conversion. First, a thorough discussion on PQDSCs, their structure, surface treat-ment, and interface engineering along with their recent progress are presented. It is highlighted that the improvement of the efficiency of PQDSCs from below 10% to beyond 16% in a matter of a few years has turned them into promising candidates for future SC applications. Subsequently, the application of PQDs in photocatalytic reactions such as hydrogen production, CO2 reduction, and organic compounds' degradation is summarized. Not to mention that, despite the remarkable properties of PQDs in SCs and photocatalysis, the inferior stability of PV devices based thereon under operation as well as their poor tolerance under air, water, light, and heat impede their widespread application. For this, the practical efforts and possible solutions are extensively addressed. Finally, an outlook is provided, addressing further merits, and demerits of each application as well as prospective opportunities.
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    PublicationOpen Access
    Metal doped layered MgB2 nanoparticles as novel electrocatalysts for water splitting
    (Nature Publishing Group (NPG), 2021) Khatamian, Masoumeh; N/A; Department of Chemistry; Department of Chemistry; Sadeghi, Ebrahim; Peighambardoust, Naeimeh Sadat; Ünal, Uğur; Aydemir, Umut; PhD Student; Researcher; Faculty Member; Faculty Member; Koç University AKKİM Boron-Based Materials _ High-technology Chemicals Research _ Application Center (KABAM) / Koç Üniversitesi AKKİM Bor Tabanlı Malzemeler ve İleri Teknoloji Kimyasallar Uygulama ve Araştırma Merkezi (KABAM); Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); Graduate School of Sciences and Engineering; College of Sciences; N/A; N/A; 42079; 58403
    Growing environmental problems along with the galloping rate of population growth have raised an unprecedented challenge to look for an ever-lasting alternative source of energy for fossil fuels. The eternal quest for sustainable energy production strategies has culminated in the electrocatalytic water splitting process integrated with renewable energy resources. The successful accomplishment of this process is thoroughly subject to competent, earth-abundant, and low-cost electrocatalysts to drive the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), preferably, in the same electrolyte. The present contribution has been dedicated to studying the synthesis, characterization, and electrochemical properties of newfangled electrocatalysts with the formal composition of Mg1-xTMxB2 (x=0.025, 0.05, and 0.1; TM (transition metal)=Fe and Co) primarily in HER as well as OER under 1 M KOH medium. The electrochemical tests revealed that among all the metal-doped MgB2 catalysts, Mg0.95Co0.05B2 has the best HER performance showing an overpotential of 470 mV at-10 mA cm(-2) and a Tafel slope of 80 mV dec(-1) on account of its high purity and fast electron transport. Further investigation shed some light on the fact that Fe concentration and overpotential for HER have adverse relation meaning that the highest amount of Fe doping (x=0.1) displayed the lowest overpotential. This contribution introduces not only highly competent electrocatalysts composed of low-cost precursors for the water-splitting process but also a facile scalable method for the assembly of highly porous electrodes paving the way for further stunning developments in the field.