Scholarly Publications - Chemistry

Permanent URI for this collectionhttps://hdl.handle.net/11693/115489

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Open Access
Origins of the photocatalytic NOx oxidation and storage selectivity of mixed metal oxide photocatalysts: prevalence of electron-mediated routes, surface area, and basicity
(American Chemical Society, 2024-01-23) Ebrahimi, Elnaz; Irfan, Muhammad; Koçak, Yusuf; Rostas, A. M.; Erdem, E.; Özensoy, Emrah
MgO, CaO, SrO, or BaO-promoted TiO2/Al2O3 was utilized in the photocatalytic NOx oxidation and storage reaction. Photocatalytic performance was investigated as a function of catalyst formulation, calcination temperature, and relative humidity. Onset of the photocatalytic activity in TiO2/Al2O3 coincides with the transition from the anatase to rutile phase and increasing number of paramagnetic active centers and oxygen vacancies. Disordered AlOx domains enable the formation of oxygen vacancies and paramagnetic centers on titania domains, hindering the nucleation and growth of titania particles, as well as increasing specific surface area (SSA) to store oxidized NOx species away from titania active sites. Both e-- and h+-mediated pathways contribute to photocatalytic NO conversion. Experiments performed using an e- scavenger (i.e., H2O2), suppressing the e--mediated route, attenuated the photocatalytic selectivity by triggering NO2(g) release. Superior NOx storage selectivity of 7.0Ti/Al-700 as compared to other TiO2/Al2O3 systems in the literature was attributed to an interplay between the presence of electrons trapped at oxygen vacancies and superoxide species allowing a direct pathway for the complete NO oxidation to HNO3/NO3- species, and the relatively large SSA of the photocatalyst prevents the rapid saturation of the photocatalyst with oxidation products. Longevity of the 7.0Ti/Al-700 was improved by the incorporation of CaO, emphasizing the importance of the surface basicity of the NOx storage sites.
Open Access
Tunable photocatalytic activity of CoFe Prussian blue analogue modified SrTiO3 core–shell structures for solar-driven water oxidation
(American Chemical Society, 2023-12-18) Peighambardoust, N. S.; Sadigh Akbari, Sina; Lomlu, Rana; Aydemir, U.; Karadaş, Ferdi
This study presents a pioneering semiconductor-catalyst core–shell architecture designed to enhance photocatalytic water oxidation activity significantly. This innovative assembly involves the in situ deposition of CoFe Prussian blue analogue (PBA) particles onto SrTiO3 (STO) and blue SrTiO3 (bSTO) nanocubes, effectively establishing a robust p–n junction, as demonstrated by Mott–Schottky analysis. Of notable significance, the STO/PB core–shell catalyst displayed remarkable photocatalytic performance, achieving an oxygen evolution rate of 129.6 μmol g–1 h–1, with stability over an extended 9-h in the presence of S2O82– as an electron scavenger. Thorough characterization unequivocally verified the precise alignment of the band energies within the STO/PB core–shell assembly. Our research underscores the critical role of tailored semiconductor-catalyst interfaces in advancing the realm of photocatalysis and its broader applications in renewable energy technologies.
Open Access
Nanoarchitectonics of mesoporous M2P2O7 (M = Mn(II), Co(II), and Ni(II)) and M2–xCoxP2O7 and transformation to their metal hydroxides with decent charge capacity in alkali media
(American Chemical Society, 2024-10-02) Ulu, Işıl; Ulgut, Burak; Dağ, Ömer
A general synthetic method has been developed to synthesize spherical mesoporous metal pyrophosphate (m-M2P2O7) particles and to fabricate graphite rod-coated (GR-M2P2O7) electrodes, which are important as energy storage materials. The clear aqueous solution of the ingredients (namely, [M(H2O)6](NO3)2, H4P2O7, water, and P123) assembles, upon excess water evaporation, into a mesostructured M2HxP2O7(NO3)x·nH2O–P123 semisolid that is calcined to produce the spherical m-M2P2O7 (where M is Ni, Co, Mn, Ni/Co, or Mn/Co) particles, coated over GR, and calcined to fabricate the GR-M2P2O7 electrodes. The mesostructured and mesoporous materials are characterized using diffraction (XRD), spectroscopy (ATR-FTIR, XPS, and EDX), N2 adsorption–desorption, and imaging (SEM and TEM) techniques. The electrochemical/chemical investigations showed that the GR-M2P2O7 electrodes transform to β-M(OH)2 in alkali media. The spherical m-Ni2P2O7 particles transform into spherical ultrathin nanoflakes of β-Ni(OH)2. However, the m-Mn2P2O7 and m-Co2P2O7 particles transform to much thicker β-Mn(OH)2 and β-Co(OH)2 plate-like nanoparticles, respectively. The size and morphology of the β-M(OH)2 particle depend on the Ksp of the M2P2O7 and determine the charge capacity (CC) and specific capacitance (SC) of the electrodes. The β-Ni(OH)2 and β-Ni0.67Co0.33(OH)2 electrodes display high CC (129 and 170 mC/cm2, respectively) and SC (234.5 and 309 mF/cm2, respectively) values. However, these values are almost 10× smaller in β-Mn(OH)2, β-Co(OH)2, β-Mn1–xCox(OH)2, and cobalt-rich β-Ni1–xCox(OH)2 electrodes.
Open Access
Bioaromatic-associated multifunctionality in lignin-containing reversible elastomers
(American Chemical Society, 2023-07-12) Thys, Marlies; Kaya, Görkem Eylül; Soetemans, Lise; Van Assche, Guy; Bourbigot, Serge; Baytekin, Bilge; Vendamme, Richard; Van den Brande, Niko
The unique molecular structure of lignin, intrinsically rich in bioaromatic groups (phenolic hydroxyls), gives it, e.g., antioxidant, antistatic, antimicrobial, UV-blocking, hydrophobic, or even flame-retardant properties, which are highly interesting. An attractive strategy to use lignin as a macro-monomer for the design of functional materials that retain certain of these lignin-specific properties is to partially preserve some phenolic groups during the synthesis. In this work, we explore the properties of reversible elastomers containing a lignin fraction whose phenolic groups have only been partially modified. To do so, Kraft lignin was first fractionated and partially (89%) modified with furan groups, allowing its homogeneous incorporation in Diels-Alder formulations. The effect of the residual phenolic groups embedded in the polymer matrix was then systematically studied, focusing on the specific material properties associated with lignin. The obtained lignin-containing networks notably showed increased radical scavenging activity (which directly resulted in improved antistatic and antioxidant properties), displayed improved UV absorbance due to the presence of multiple lignin chromophores, and were even able to inhibit the growth of bacteria. This article demonstrates that tailored and partially modified lignin fractions could be used as multi-functional building blocks for the design of complex (and reversible) polymer architectures, mimicking some of the unique lignin functionalities found in nature, and this without the need to add specific additives.
Open Access
Core-shell quantum dot-embedded polymers for antistatic applications
(American Chemical Society, 2023-12-07) Ekim, Sunay Dilara; Aydın, Firdevs; Kaya, Görkem Eylül; Baytekin, H. Tarık; Asil, Demet; Baytekin, Bilge
Electrical charges develop on the surfaces of two insulator materials when they are in contact and separated. The retention of charges on insulator polymers causes material losses and hazards in industries using these polymers. Here, we show that a set of core-shell quantum dots embedded into a common polymer can destabilize the charges on the polymer. The locations of the charge carriers in the nanostructure, or the “type” of the dots, affect their discharging ability, which can also be manipulated or reverted remotely by light. The mechanism of antistatic action is presumed to contain interaction with polymer mechanospecies. The quantum dot embedding renders the polymers antistatic without changing their conductivity. Such antistatic additives, by which the polymers remain insulating, can be used to prevent static charges, e.g., in electronic coatings and in other antistatic applications.
Open Access
Access to symmetrical and unsymmetrical cyclobutanes via template directed [2+2] photodimerization reactions of cinnamic acids
(Georg Thieme Verlag, 2023-08-16) Yağcı, Bilge Banu; Munir, Badar; Zorlu, Y.; Türkmen, Yunus Emre
In this work, we have developed a general and broadly applicable template-directed photochemical [2+2]-cycloaddition reaction which provides access to a wide range of symmetrical and unsymmetrical cyclobutane products. The use of 1,8-dihydroxynaphthalene as a covalent template paved the way for successful and highly selective photochemical homodimerization and heterodimerization reactions in the solid state between cinnamic acid derivatives. Notably, the method works equally well with aryl- and heteroaryl-containing substrates leading to the formation of β-truxinic acid analogues as single diastereomers and in high yields (up to 99%).
Open Access
Complex patterning of matter with liesegang patterns propagating through different concentration media─gel lenses for liesegang waves
(American Chemical Society, 2023-11-18) Akbulut, Elif Sıla; Holló, Gábor; Lagzi, Istvan; Baytekin, Bilge
The patterns formed in natural biochemical and geochemical media are never spatially or geometrically homogeneous. On the other hand, the artificial systems trying to mimic nature are usually homogeneous and far from depicting the complexity of the natural ones. Liesegang patterns (LPs) are artificial reaction-diffusion precipitate patterns that can be formed in hydrogels. Although these patterns can be made to “sense” the environment, they are mostly formed in homogeneous media. Here, we present that a simple setting of different gel concentration boundaries can cause refractions of the pattern waves and changes in the band spacings. The extent of refraction is dependent on the macroscopic shape of the boundary. As imaged by scanning electron microscopy, the LP bands “crossing the boundaries” are formed by the product of a new morphology. This study can be a step forward in straightforwardly achieving complexity in artificial systems and developing new crystal forms of solids.
Embargo
Three in one: three different molybdates trapped in a thiacalix[4]arene protected ag72 nanocluster for structural transformation and photothermal conversion
(John Wiley & Sons, 2024-01-15) Wang, Z.; Zhu, Y.; Ahlstedt, O.; Konstantinou, K.; Akola, J.; Tung, C.; Alkan, Fahri; Sun, D.
Polyoxometalates (POMs) represent crucial intermediates in the formation of insoluble metal oxides from soluble metal ions, however, the rapid hydrolysis-condensation kinetics of MoVI or WVI makes the direct characterization of coexisted molecular species in a given medium extremely difficult. Silver nanoclusters have shown versatile capacity to encapsulate diverse POMs, which provides an alternative scene to appreciate landscape of POMs in atomic precision. Here, we report a thiacalix[4]arene protected silver nanocluster (Ag72b) that simultaneously encapsulates three kinds of molybdates (MoO42−, Mo6O228− and Mo7O258−) in situ transformed from classic Lindqvist Mo6O192−, providing more deep understanding on the structural diversity and condensation growth route of POMs in solution. Ag72b is the first silver nanocluster trapping so many kinds of molybdates, which in turn exert collective template effect to aggregate silver atoms into a nanocluster. The post-reaction of Ag72b with AgOAc or PhCOOAg produces a discrete Ag24 nanocluster (Ag24a) or an Ag28 nanocluster based 1D chain structure (Ag28a), respectively. Moreover, the post-synthesized Ag28a can be utilized as potential ignition material for further application. This work not only provides an important model for unlocking dynamic features of POMs at atom-precise level but also pioneers a promising approach to synthesize silver nanoclusters from known to unknown.
Open Access
Lyotropic liquid crystalline mesophases of lithium dihydrogen phosphate and 10-lauryl ether stabilized with water or phosphoric acid
(Wiley, 2023-01) Topuzlu, Ezgi Yılmaz; Ulgut, Burak; Dağ, Ömer
Open Access
Enhancing oxygen evolution catalytic performance of nickel borate with cobalt dopingand carbon nanotubes
(Wiley, 2023-02-16) Enez, S.; Karani Konuksever, V.; Samuei, S.; Karadaş, Ferdi; Ülker, E.
Open Access
A dormant reagent reaction-diffusion method for the generation of Co-Fe Prussian Blue analogue periodic precipitate particle libraries
(Wiley-VCH GmbH, 2023-08-25) Tootoonchian, Pedram; Kwiczak-Yiğitbaşı, Joanna; Turab Ali Khan, Muhammad; Chalil Oglou, Ramadan; Holló, G.; Karadaş, Ferdi; Lagzi, I.; Baytekin, Bilge
Liesegang patterns that develop as a result of reaction-diffusion can simultaneously form products with slightly different sizes spatially separated in a single medium. We show here a reaction-diffusion method using a dormant reagent (citrate) for developing Liesegang patterns of cobalt hexacyanoferrate Prussian Blue analog (PBA) particle libraries. This method slows the precipitation reaction and produces different-sized particles in a gel medium at different locations. The gel-embedded particles are still catalytically active. Finally, the applicability of the new method to other PBAs and 2D systems is presented. The method proves promising for obtaining similar inorganic framework libraries with catalytic abilities. © 2023 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.
Embargo
Rational design of an acceptor-chromophore-relay-catalyst tetrad assembly for water oxidation
(Royal Society of Chemistry, 2023-12-25) Chalil Oglou, Ramadan; Ulusoy Ghobadi, T. Gamze; Saylam, A.; Bese, D.; Bese, C.; Yağlıoğlu, Halime Gül; Özçubukçu, S.; Özbay, Ekmel; Karadaş, Ferdi
Open Access
Interaction of CO2 with MnOx/Pd(111) reverse model catalytic interfaces
(Wiley, 2023-07-03) Anıl, Arca; Sadak, Ömer Faruk; Karakurt, Bartu; Koçak, Yusuf; Lyubinetsky, Igor; Özensoy, Emrah
Understanding the activation of CO2 on the surface of the heterogeneous catalysts comprised of metal/metal oxide interfaces is of critical importance since it is not only a prerequisite for converting CO2 to value-added chemicals but also often, a rate-limiting step. In this context, our current work focuses on the interaction of CO2 with heterogeneous bi-component model catalysts consisting of small MnOx clusters supported on the Pd(111) single crystal surface. These metal oxide-on-metal ‘reverse’ model catalyst architectures were investigated via temperature programmed desorption (TPD) and x-ray photoelectron spectroscopy (XPS) techniques under ultra-high vacuum (UHV) conditions. Enhancement of CO2 activation was observed upon decreasing the size of MnOx nanoclusters by lowering the preparation temperature of the catalyst down to 85 K. Neither pristine Pd(111) single crystal surface nor thick (multilayer) MnOx overlayers on Pd(111) were not capable of activating CO2, while CO2 activation was detected at sub-monolayer (∼0.7 ML) MnOx coverages on Pd(111), in correlation with the interfacial character of the active sites, involving both MnOx and adjacent Pd atoms. © 2023 The Authors. ChemPhysChem published by Wiley-VCH GmbH.
Open Access
Intramolecular through-space charge transfer between benzofuran and ynone groups on a naphthalene spacer
(Royal Society of Chemistry, 2023-12-07) Çalıkyılmaz, Eylül; Karaoğlu, Gözde; Demir, M.; Şahin, O.; Ulgut, Burak; Akdağ, A.; Türkmen, Yunus Emre
Embargo
Understanding the role of water in the lyotropic liquid crystalline mesophase of high performance flexible supercapacitor electrolytes using a rheological approach
(Elsevier, 2024-01-15) Özkaynak, M. U.; Kocaağa, B.; Dönmez, K. B.; Dağlar, S.; Tuerker, Y.; Karatepe, N.; Güner, F. S.; Dağ, Ömer
The effect of water on the structure, properties, and flexibility of lyotropic liquid crystalline (LLC) C12E23-LiCl-H2O gel electrolytes was explored. Structural techniques, such as X-ray Diffraction (XRD), Polarized Optical Microscopy (POM), and five dynamic measurements, were employed to examine the rheological properties of the LLC mesophase across various water contents. These analyses provided quantitative insights into the influence of water content and LiCl concentration on gel strength, gelation point, and structural recovery. The three-dimensional network of the gel encapsulates Li+ and Cl− ions within hydrophilic domains, showing significant performance in supercapacitor applications. The observed increase in storage modules with decreasing water content is attributed to variations in the quantity and average size of junction points owing to system entanglement. These research findings highlight that excess water molecules, which break down micellar connections, are responsible for the weakening of the gel. Conversely, at low water concentrations, the micellar domains entangle, displaying viscoelastic behavior akin to that of a transitory polymer network.
Open Access
Photocatalytic CO2 conversion: Beyond the earth
(Elsevier, 2023-07-25) Low, J.; Zhang, C.; Karadaş, Ferdi.; Xiong, Y.
The issue of climate change attributed to CO2 emissions has led to increased attention towards the study and development of artificial photosynthesis through photocatalytic CO2 conversion to recon‐struct the broken carbon cycle in nature. Photocatalytic CO2 conversion can simultaneously reduce the CO2 concentration in the atmosphere and produce valuable hydrocarbon fuels. With the recent discovery of abundant reserves of CO2 and water at extraterrestrial sites, it has been proposed that photocatalytic CO2 conversion can also be implemented at extraterrestrial sites to build up an artificial carbon cycle for providing propellants and life support for space missions. This comment presents our perspectives on the development of photocatalytic CO2 conversion beyond Earth, with a focus on its general principles and potential challenges that may arise at extraterrestrial sites. Finally, a brief overview of the future research directions in this field is presented.
Embargo
On the use of drift correction for electrochemical impedance spectroscopy measurements
(Elsevier, 2023-02-01) Orazem, M.E.; Ulgut, Burak
The effectiveness of drift correction is explored for measurement of electrochemical impedance spectra. Numerical simulations and experimental data for batteries and capacitors are used to show that drift correction cannot generate Kramers–Kronig consistent data for nonstationary systems. Application of drift correction improves, but does not fully recover, the original spectrum that is not corrupted by the drift. Drift correction improved the quality of spectra obtained for stationary systems under galvanostatic modulation, where the change from one frequency to another caused initial transients that corrupted the measurement.
Open Access
Wave-packet solution of time-dependent Faddeev Equations using a mixed basis in Jacobi and Hypersherical Momenta
(Springer Wien, 2024-06-19) Kuruoğlu, Zeki Cemal
Having demonstrated in a recent study that the wave packet method based on the time-dependent Faddeev equations (abbreviated as TDFE-WP method) provide a viable computational tool for three-particle scattering problems, a variant of the said method is explored in the present study. In the TDFE-WP method, each Faddeev component of the time-dependent wave-packet is expanded in a basis appropriate for the corresponding rearrangement. In the present version, the basis for each rearrangement consists of a Jacobi subset suitable to describe the spectator-bound pair final states and another subset that is more appropriate for three free particles. The expectation that such a mixed basis may be more efficient to describe the time evolution of Faddeev components is borne out by present calculations.
Open Access
Fabrication of mesoporous nickel pyrophosphate electrodes and their transformation to nickel hydroxide with decent capacitance in alkaline media
(Royal Society of Chemistry, 2023-10-09) Ulu, Işıl; Ulgut, Burak; Dağ, Ömer
The development of high-energy-density electrodes is paramount for the advancement of renewable and clean energy storage materials. In this study, we have devised a synthetic approach to fabricate mesoporous Ni2P2O7 (m-NiPP) electrodes with a decent charge capacity. The method involves the formation of a liquid crystalline mesophase from an aqueous solution containing nickel nitrate hexahydrate salt (Ni(II)), pyrophosphoric acid (PPA), and a non-ionic surfactant (P123). The mesophase solidifies through the polymerization of Ni(II) ions and PPA, ultimately forming a mesostructured Ni2HxP2O7(NO3)x·nH2O semi-solid, which can be subsequently calcined to yield mesoporous Ni2P2O7 (m-NiPP). The gelation and polymerization process can be monitored using gravimetric, ATR-FTIR, XRD, and POM techniques as water evaporates during the transformation. The results reveal that the reaction between the Ni(II) ion and PPA initiates in the solution phase, continues in the gel phase, and concludes upon gentle heating. The same clear aqueous solution can be coated onto a substrate, such as FTO or graphite rods, and then calcined at various temperatures to produce the m-NiPP electrodes, composed of spherical mesoporous NiPP particles. These electrodes remain amorphous over a wide temperature range, but crystallize at approximately 700 °C while retaining their porous structure. However, when exposed to a 3 M KOH solution, the spherical m-NiPP particles undergo a transformation into β-Ni(OH)2 particles. These transformed particles are approximately 1.5 nm thick, equivalent to 3–4 layers, and 7 nm wide, all while maintaining their spherical morphology. This transformation process occurs rapidly for amorphous m-NiPP and proceeds more slowly in the case of crystalline m-NiPP. The resulting electrodes exhibit a substantial charge capacity of 422 C g−1 and an impressive specific capacitance of over 1407 F g−1.
Open Access
Manipulating intermetallic charge transfer for switchable external stimulus-enhanced water oxidation electrocatalysis
(John Wiley and Sons Inc, 2023-10-26) Chalil Oglou, Ramadan; Ulusoy Ghobadi, Türkan Gamze; Hegner, F. S. .; Galán-Mascarós, J. R.; López, N; Özbay, Ekmel; Karadaş, Ferdi
Electrocatalytic processes involving the oxygen evolution reaction (OER) present a kinetic bottleneck due to the existence of linear-scaling relationships, which bind the energies of the different intermediates in the mechanism limiting optimization. Here, we offer a way to break these scaling relationships and enhance the electrocatalytic activity of a Co−Fe Prussian blue modified electrode in OER by applying external stimuli. Improvements of ≈11 % and ≈57 % were achieved under magnetic field (0.2 T) and light irradiation (100 mW cm−2), respectively, when working at fixed overpotential, η=0.6 V at pH 7. The observed enhancements strongly tie in with the intermetallic charge transfer (IMCT) intensity between Fe and Co sites. Density Functional Theory simulations suggest that tuning the IMCT can lead to a change of the OER mechanism to an external stimuli-sensitive spin crossover-based pathway, which opens the way for switchable electrocatalytic devices.