| 1. |
- Abdi, Zahra, et al.
(författare)
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In Situ Synthesis of Manganese Oxide as an Oxygen-Evolving Catalyst : A New Strategy
- 2021
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Ingår i: Chemistry - A European Journal. - : John Wiley & Sons. - 0947-6539 .- 1521-3765. ; 27:4, s. 1330-1336
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Tidskriftsartikel (refereegranskat)abstract
- All studies on oxygen-evolution reaction by Mn oxides in the presence of cerium(IV) ammonium nitrate (CAN) have been so far carried out by synthesizing Mn oxides in the first step. And then, followed by the investigation of the Mn oxides in the presence of oxidants for oxygen-evolution reaction (OER). This paper presents a case study of a new and promising strategy for in situ catalyst synthesis by the adding Mn-II to either CAN or KMnO4/CAN solution, resulting in the formation of Mn-based catalysts for OER. The catalysts were characterized by scanning electron microscopy, energy-dispersive spectroscopy, transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, X-ray absorption spectroscopy, and X-ray photoelectron spectroscopy. Both compounds contained nano-sized particles that catalyzed OER in the presence of CAN. The turnover frequencies for both catalysts were 0.02 (mmolO2 /mol(Mn).
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| 2. |
- Behrouzi, Leila, et al.
(författare)
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Electrochemical alcohols oxidation mediated by N-hydroxyphthalimide on nickel foam surface
- 2020
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 10:1
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Tidskriftsartikel (refereegranskat)abstract
- Alcohol to aldehyde conversion is a critical reaction in the industry. Herein, a new electrochemical method is introduced that converts 1 mmol of alcohols to aldehydes and ketones in the presence of N-hydroxyphthalimide (NHPI, 20 mol%) as a mediator; this conversion is achieved after 8.5 h at room temperature using a piece of Ni foam (1.0 cm2) and without adding an extra-base or a need for high temperature. Using this method, 10 mmol (1.08 g) of benzyl alcohol was also successfully oxidized to benzaldehyde (91%) without any by-products. This method was also used to oxidize other alcohols with high yield and selectivity. In the absence of a mediator, the surface of the nickel foam provided oxidation products at the lower yield. After the reaction was complete, nickel foam (anode) was characterized by a combination of scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), X-ray absorption spectroscopy (XAS), X-ray photoelectron spectroscopy (XPS), and spectroelectrochemistry, which pointed to the formation of nickel oxide on the surface of the electrode. On the other hand, using other electrodes such as Pt, Cu, Fe, and graphite resulted in a low yield for the alcohol to aldehyde conversion.
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| 3. |
- Khan, M. Ajmal, et al.
(författare)
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Synthesize and characterization of ceria based nano-composite materials for low temperature solid oxide fuel cell
- 2018
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Ingår i: International journal of hydrogen energy. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0360-3199 .- 1879-3487. ; 43:12, s. 6310-6317
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Tidskriftsartikel (refereegranskat)abstract
- The present study is focused on ceria based mixed (ionic and electronic conductor) composite Al0.05Ni0.1Ti0.05Zn0.80-SDC (ATZN-SDC) oxide material was prepared by solid state reaction, which can be used as anode materials for solid oxide fuel cell. The effect of Ti and Al oxides were analyzed on the NiZn-SDC composite with respect to its conductivity and catalytic activity in hydrogen atmosphere. The average crystallite size of the composite was found to be 40-100 nm by XRD and SEM. The DC conductivity was determined by 4-probe technique. The electrochemical impedance spectrum (EIS) was also examined in hydrogen atmosphere within a temperature range of 350-550 degrees C. The maximum power density 370 mW/cm(2) was achieved at 650 degrees C.
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| 4. |
- Moghaddam, Navid Jameei, et al.
(författare)
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A Chemical Evolution-Like Method to Synthesize a Water-Oxidizing Catalyst
- 2021
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Ingår i: ChemElectroChem. - : John Wiley & Sons. - 2196-0216. ; 8:23, s. 4612-4617
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Tidskriftsartikel (refereegranskat)abstract
- The development of new procedures for synthesizing new, low-cost, and stable metal oxides for the oxygen-evolution reaction (OER) by water oxidation is critical. Since the 2000s, there has been a rapid rise in the use of first-row transition metal (hydr)oxides for the OER. However, there is still a need to design and synthesize an efficient and stable catalyst for the OER. The present paper aims to design and synthesize an OER catalyst based on "a look at nature" strategy. In a simple and chemical evolution-like experiment, for the first time, a solution composed of various perchlorate cations, namely, Li(I), Mg(II), Ca(II), Al(III), Mn(II), Fe(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II), Ba(II), and Na2SiO3, at a concentration of 1.0 mM at pH=4 and a potential of 1.40 V vs. NHE, which was under stirring for 15 days, was investigated. The stable OER catalyst on the electrode was characterized by X-ray absorption spectroscopy, scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. Based on the extrapolation of the Tafel plot, the onset of the OER in the presence of this catalyst was 130 mV lower than a bare electrode without it. This approach could be a roadmap to design and synthesize new and stable catalysts.
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| 5. |
- Mousazade, Younes, et al.
(författare)
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A synthetic manganese-calcium cluster similar to the catalyst of Photosystem II : challenges for biomimetic water oxidation
- 2020
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Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 49:17, s. 5597-5605
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Tidskriftsartikel (refereegranskat)abstract
- Herein, we report the synthesis, characterization, crystal structure, density functional theory calculations, and water-oxidizing activity of a pivalate Mn-Ca cluster. All of the manganese atoms in the cluster are Mn(iv) ions and have a distorted MnO6 octahedral geometry. Three Mn(iv) ions together with a Ca(ii) ion and four-oxido groups form a cubic Mn3CaO4 unit which is similar to the Mn3CaO4 cluster in the water-oxidizing complex of Photosystem II. Using scanning electron microscopy, transmission electron microscopy, energy dispersive spectrometry, extended X-ray absorption spectroscopy, chronoamperometry, and electrochemical methods, a conversion into nano-sized Mn-oxide is observed for the cluster in the water-oxidation reaction.
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| 6. |
- Mousazade, Younes, et al.
(författare)
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Revisiting Metal-Organic Frameworks for Oxygen Evolution : A Case Study
- 2020
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Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 59:20, s. 15335-15342
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Tidskriftsartikel (refereegranskat)abstract
- Water splitting is a promising reaction for storing sustainable but intermittent energies. In water splitting, water oxidation is a bottleneck, and thus different catalysts have been synthesized for water oxidation. Metal-organic frameworks (MOFs) are among the highly efficient catalysts for water oxidation, and so far, MOF-based catalysts have been divided into two categories: MOF-derived catalysts and direct MOF catalysts. In particular, a nickel/cobalt MOF is reported to be one of the best direct catalysts for water oxidation. For the first-row transition MOF structures in general, a hypothesis is that the harsh conditions of OER could cause the decomposition of organic ligands and the formation of water-oxidizing oxide-based structures. By electrochemical methods, scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, and X-ray absorption spectroscopy, a nickel/cobalt MOF known to be a highly efficient catalyst for water oxidation is shown to form Ni/Co oxide, making it a candidate catalyst for oxygen evolution. MOFs are interesting precatalysts for metal oxide water-oxidizing catalysts, but control experiments are necessary for determining whether a certain MOF or other MOFs are true catalysts for OER. Thus, finding a true and direct MOF electrocatalyst for OER is a challenge.
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| 7. |
- Mousazade, Younes, et al.
(författare)
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Water oxidation by a manganese-potassium cluster : Mn oxide as a kinetically dominant "true" catalyst for water oxidation
- 2018
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Ingår i: Catalysis Science & Technology. - : Royal Society of Chemistry (RSC). - 2044-4753 .- 2044-4761. ; 8:17, s. 4390-4398
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Tidskriftsartikel (refereegranskat)abstract
- Nature uses an Mn cluster for water oxidation, and thus, water oxidation using Mn clusters is interesting when used in artificial water-splitting systems. An important question is whether an Mn cluster is a true catalyst for water oxidation or not. Herein, an Mn-K cluster was investigated for electrochemical water oxidation to find the true and the kinetically dominant catalyst using X-ray absorption spectroscopy, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, and electrochemical methods. The experiments showed that conversion into nanosized Mn oxide occurred for the cluster, and the nanosized Mn oxides are the true catalyst for water oxidation.
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| 8. |
- Zand, Zahra, et al.
(författare)
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Nickel-Vanadium Layered Double Hydroxide under Water-Oxidation Reaction : New Findings and Challenges
- 2019
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Ingår i: ACS Sustainable Chemistry and Engineering. - : AMER CHEMICAL SOC. - 2168-0485. ; 7:20, s. 17252-17262
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Tidskriftsartikel (refereegranskat)abstract
- Nickel-vanadium layered double hydroxide has recently been considered as a highly active, low-cost electrocatalyst and as a benchmark non-noble metal-based electrocatalyst for water oxidation. The material showed a current density of 27 mA/cm(2) at an overpotential of 350 mV, which is comparable to the best-performing nickel-iron-layered double hydroxides for water oxidation in alkaline media. The enhanced conductivity and facile electron transfer were suggested among important factors for the high activity of nickel-vanadium layered double hydroxide. In the present study, the stability of an Ni-V catalyst was investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), X-ray absorption near edge structure (XANES), extended X-ray absorption fine structure (EXAFS), and electrochemical characterization methods. These methods show that the initial Ni-V catalyst during water oxidation in alkaline conditions is converted from an initial alpha-Ni(OH)(2) phase to a partially oxidized alpha-Ni(OH)(2/)NiOOH phase and VO(4)(3-)ions. We carefully evaluate the stability of the catalysts and analyze the compositional changes during prolonged water-oxidation conditions using inductively coupled plasma-optical emission spectroscopy (ICP-OES). The experiments using both Fe-free electrolyte and Fe-free nickel-vanadium layered double hydroxide reveal that vanadium do not affect the water-oxidizing activity of alpha-Ni(OH)(2).
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| 9. |
- Zand, Zahra, et al.
(författare)
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Role of decomposition products in the oxidation of cyclohexene using a manganese(III) complex
- 2023
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Ingår i: Communications Chemistry. - : Springer Nature. - 2399-3669. ; 6:1
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Tidskriftsartikel (refereegranskat)abstract
- Metal complexes are extensively explored as catalysts for oxidation reactions; molecular-based mechanisms are usually proposed for such reactions. However, the roles of the decomposition products of these materials in the catalytic process have yet to be considered for these reactions. Herein, the cyclohexene oxidation in the presence of manganese(III) 5,10,15,20-tetra(4-pyridyl)-21H,23H-porphine chloride tetrakis(methochloride) (1) in a heterogeneous system via loading the complex on an SBA-15 substrate is performed as a study case. A molecular-based mechanism is usually suggested for such a metal complex. Herein, 1 was selected and investigated under the oxidation reaction by iodosylbenzene or (diacetoxyiodo)benzene (PhI(OAc)(2)). In addition to 1, at least one of the decomposition products of 1 formed during the oxidation reaction could be considered a candidate to catalyze the reaction. First-principles calculations show that Mn dissolution is energetically feasible in the presence of iodosylbenzene and trace amounts of water. Metal complexes are often used as catalysts for oxidation reactions, however, there are open questions about the role of the decomposition products in the catalytic process. Here, the authors explore the potential role of decomposition products in the oxidation of cyclohexene using a manganese(III) complex catalyst adsorbed on an SBA-15 substrate.
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