Scholarly Publications - Chemistry
Permanent URI for this collectionhttps://hdl.handle.net/11693/115489
Browse
Recent Submissions
Item Embargo Electrochemical Impedance Spectroscopy (EIS) and non-linear harmonic analysis (NHA) of Li-SOCl2/SO2Cl2 batteries(Pergamon-Elsevier Science Ltd., 2024-03-20) Katırcı, Gökberk; Civan, Fazlı Eren; Jung, Sunghoon; Lee, Chae Bong; Ülgüt, BurakElectrochemical Impedance Spectroscopy (EIS) is a valuable tool for characterizing primary lithium batteries. Before fitting the spectrum, the so-called Kramers-Kronig(KK) method has to be checked for the reliability and accuracy of the EIS spectrum. The decision to further fit and analyze the spectrum for physical events in the system is made after checking the KK compatibility of the spectrum. In this paper, we propose further confirmation of the reliability and the accuracy of the EIS spectrum by using the Non-linear harmonic analysis (NHA) of the measurement. The study shows that the KK-compatible EIS spectrum shows homogeneous higher harmonics results where one can further verify the spectrum. The phase of the excitation signal and its effects on the NHA are discussed. A measurement method for measuring Li/SOCl2 and SO2Cl2 batteries to obtain the KK-compatible EIS spectrum is introduced.Item Embargo Insights into charge transfer dynamics of Li batteries through temperature-dependent electrochemical impedance spectroscopy (EIS) utilizing symmetric cell configuration(Pergamon-Elsevier Science Ltd., 2024-05-01) Zabara, Mohammed A.; Katırcı, Gökberk; Civan, Fazlı Eren; Yürüm, Alp; Gürsel, Selmiye A.; Ülgüt, BurakStudying charge transfer processes in Li batteries poses a challenge due to their complicated nature and the battery's inherent inertness. While electrochemical impedance spectroscopy (EIS) offers a promising approach to investigating these processes, its effectiveness is hindered by the complexity of the data generated and the ambiguity in the analyses. Here, we demonstrate that the assignment process is not straightforward for complex secondary Li batteries, and it necessitates additional measurements and in-depth analysis. We first performed simplification of the impedance data by employing symmetric cell configurations to obtain charge transfer resistance values for each electrode. We second took advantage of altering three parameters during the EIS measurement: electrolyte composition, measurement temperature, and the state of health to extract important parameters related to both the anodic and cathodic charge transfer mechanisms. The analysis enabled the correlation of the observed charge transfer resistances to the corresponding electrochemical process and to obtain the kinetic parameters of the studied process. Our work illustrates how EIS can be used to study and understand the intricate electrochemical charge transfer processes in Li batteries, which are difficult to explore using alternative techniques.Item Open Access Molten Salt Assisted Assembly (MASA) of novel mesoporous Ni0.5Mn0.5Co2O4 for high-performance asymmetric supercapacitors(Elsevier Science Inc., 2024-11) Özkaynak, Mert Umut; Türker, Yurdanur; Dönmez, Koray Bahadır; Dağlar, Selin; Çobandede, Zehra; Çelenk, Merve Metin; Karatepe, Nilgi; Güner, F. Seniha; Dağ, ÖmerMesoporous transition metal oxides (TMO) are immensely investigated as electrode materials in supercapacitors. The molten salt assisted self-assembly (MASA) process enables a facile route for the synthesis of the mesoporous TMO. In this study, mesoporous nickel manganese cobaltite (Ni0.5Mn0.5Co2O4) is synthesized for the first time using a MASA process and is evaluated as a novel electrode-active material for asymmetric supercapacitors. The objective of this work is to quantitatively measure the performance improvement in the Ni0.5Mn0.5Co2O4 electrode based on its composition and reveal the improvement mechanism through electrochemical methods. The electrochemical performance of the NiCo2O4 and MnCo2O4 prepared by MASA is also investigated, in order to understand the synergistic effect of Ni and Mn elements in the same cobaltite structure. In line with the data obtained from half cells, a full asymmetric cell is prepared by assembling the appropriate amount of Ni0.5Mn0.5Co2O4 and activated carbon through the charge balance theory. The test results show that the specific capacitance CA (Cs) values are 2.62F/cm2 (92.1F/g) for mesoporous NiCo2O4, 0.26F/cm2 (9.8F/g) for mesoporous MnCo2O4, and 9.53F/cm2 (338.5F/g) for mesoporous Ni0.5Mn0.5Co2O4 under the test conditions of 5 mA/cm2. The asymmetric supercapacitor assembled with Ni0.5Mn0.5Co2O4 and activated carbon demonstrates a superior energy density of 79.52 Wh/kg at 1 mA/cm2. The findings of the study highlight the importance of substituting the electrode with Ni0.5Mn0.5Co2O4 to enhance the CA (Cs) by achieving proper surface properties and electrochemical activity.Item Embargo Recent advances in the synthesis and applications of fluoranthenes(Royal Society of Chemistry, 2025-03-04) Turkmen, Yunus EmreAs an important subclass of polycyclic aromatic hydrocarbons (PAHs), fluoranthenes continue to attract significant attention in synthetic organic chemistry and materials science. In this article, an overview of recent advances in the synthesis of fluoranthene derivatives along with selected applications is provided. First, methods for fluoranthene synthesis with a classification based on strategic bond disconnections are discussed. Then, the total syntheses of natural products featuring the benzo[j]fluoranthene skeleton are covered. Finally, examples of important applications of a variety of fluoranthenes are summarized.Item Embargo Electronic synergistic effects on the stability and oxygen evolution reaction efficiency of the mesoporous LiMn2-x M x O4 (M = Mn, Fe, Co, Ni, and Cu) electrodes(American Chemical Society, 2024-11-07) Durukan, Irmak Karakaya; Dağ, ÖmerStable porous manganese oxide-based electrodes are essential for clean energy generation and storage because of their high natural abundance and health safety. This investigation focuses on mesoporous LiMn2-x M x O4 (where M is Fe, Co, Ni, and Cu and x is 0, 0.1, 0.3, 0.5, and 0.67) electrodes and thin/thick films. The mesoporous electrodes and films are fabricated by coating clear and homogeneous ethanol solutions of the salts (LiNO3, [Mn(OH2)4](NO3)2, and [M(OH2) x ](NO3)2) and surfactants (P123 and CTAB) and calcining at elevated temperature (denoted as F-LiMn2-x M x O4, G-LiMn2-x M x O4, and meso-LiMn2-x M x O4, respectively). The electrochemical properties, stability, and oxygen evolution reaction (OER) performance of the F/G-LiMn2-x M x O4 electrodes are investigated in alkaline media using a three electrode setup. The F-LiMn1.33M0.67O4 electrodes (where M is Mn, Fe, Co, and Ni) exhibit low Tafel slopes of 60, 43, 44, and 32 mV/dec, respectively. While all the Mn-rich and F-LiMn2-x Fe x O4 electrodes degrade via Mn(VI) disproportionation reaction, the 33% Co electrode shows high stability during the OER. The nickel-based electrodes are stable with as little as 15% Ni and display excellent OER performance over 25% Ni, albeit undergoing a transformation that accumulates Ni(OH)2 species on the electrode surface. Copper in the F-LiMn2-x Cu x O4 electrodes is homogeneous at low Cu percentages but forms a CuO phase above 15% Cu, undergoes degradation, and displays a weak OER performance. In short, Co and Ni stabilize the F-LiMn1.33Co0.67O4 and F-LiMn1.7Ni0.3O4 electrodes, which display excellent OER performance.Item Open Access Three in one: Three different molybdates trapped in a thiacalix arene protected Ag72 nanocluster for structural transformation and photothermal conversion(Wiley-VCH Verlag GmbH & Co. KGaA, 2023-11-28) Wang, Z.; Zhu, Y.-J.; Ahlstedt, O.; Konstantinou, K.; Akola, J.; Tung, C.-H.; Alkan, Fahri; Sun, D.Polyoxometalates (POMs) represent crucialintermediates in the formation of insoluble metal oxidesfrom soluble metal ions, however, the rapid hydrolysis-condensation kinetics of MoVI or WVI makes the directcharacterization of coexisted molecular species in agiven medium extremely difficult. Silver nanoclustershave shown versatile capacity to encapsulate diversePOMs, which provides an alternative scene to appreciatelandscape of POMs in atomic precision. Here, we reporta thiacalix[4]arene protected silver nanocluster (Ag72b)that simultaneously encapsulates three kinds of molyb-dates (MoO42 , Mo6O228 and Mo7O258 ) in situ trans-formed from classic Lindqvist Mo6O192 , providing moredeep understanding on the structural diversity andcondensation growth route of POMs in solution. Ag72bis the first silver nanocluster trapping so many kinds ofmolybdates, which in turn exert collective templateeffect to aggregate silver atoms into a nanocluster. Thepost-reaction of Ag72b with AgOAc or PhCOOAgproduces a discrete Ag24 nanocluster (Ag24a) or an Ag28nanocluster based 1D chain structure (Ag28a), respec-tively. Moreover, the post-synthesized Ag28a can beutilized as potential ignition material for further applica-tion. This work not only provides an important modelfor unlocking dynamic features of POMs at atom-preciselevel but also pioneers a promising approach to synthe-size silver nanoclusters from known to unknown.Item Open Access Transition metal salt catalysed green synthesis of mesoporous silica nanoparticles(ELSEVIER BV, 2024-06-26) Amirzhanova, Assel; Ullah, Najeeb; Dağ,ÖmerConventionally, mesoporous silica nanoparticles are prepared by catalysing silicon alkoxides using acids or bases and are highly important in storage, delivery, and catalysis. Here, for the first time, we demonstrate that a transition metal ion (such as Ni(II), Co(II), and Mn(II)) also catalyses the hydrolysis and condensation reactions of silicon alkoxides in aqueous media without any additional acid or base to synthesize mesostructured and micro/mesostructured silica nanoparticles. An aqueous solution of a transition metal salt (specifically, nitrate salts of Ni(II), Co(II), or Mn(II), or chloride and sulphate salts of Ni(II)), 10-Lauryl ether (C12H25(OCH2CH2)10OH, C12E10) and cetyltrimethylammonium bromide (C16H33N(CH3)3Br, CTAB), and tetramethyl orthosilicate (TMOS) undergoes a precipitation reaction at room temperature, yielding ultra-small ordered mesostructured silica nanoparticles. These nanoparticles are subsequently calcined to produce mesoporous silica (meso-SiO2) with a high surface area (680–871 m2/g), large pore-volume (2.2–3.71 cm3/g), and small pore-size (1.2–3.0 nm). Moreover, the counter anions of the salts play an important role in the assembly process to obtain nanoparticles with an additional well-defined secondary pore (7.5–33.4 nm or larger). Coordinated water of the metal ion and methoxy group of the silica source react to produce a complex in which two hydroxy sides are in close vicinity to speed up the condensation reaction. We propose a hydrolysis and condensation reaction mechanism for TMOS to highlight the role of the metal ion as a catalyst.Item Open Access Deciphering intramolecular charge transfer in fluoranthene derivatives(Royal Society of Chemistry, 2024-05-24) Debnath, S.; Mohanty, A.; Naik, P.; Salzner, Ulrike; Dasgupta, J.; Patil, S.An intramolecular charge transfer (ICT) state evolves via excited state structural change and solvent reorganization, where the charge distribution in the excited state is markedly different from that in the ground state. Due to its ubiquitous nature, this intriguing photophysical phenomenon offers promising applications in the realm of optoelectronics. Judicious choice of donor-acceptor-based (D-A) push-pull chromophores is the most fundamental strategy to achieve ICT state formation. In the present work, we introduce a unique class of fluoranthene-based chromophores that do not belong to the conventional D-A design principle, as the fluoranthene core is seldom used as an acceptor. Nevertheless, we observe ICT state formation upon attaching strong donor triphenylamine to the fluoranthene backbone (TPF-2TPA). Theoretical studies demonstrate that the hole and electron densities are localized over the triphenylamine and fluoranthene core, respectively, which induces ICT character in the lowest energy transition of TPF-2TPA. Solvent polarity-dependent steady-state and time-resolved spectroscopic studies confirm the formation of the ICT state. Furthermore, viscosity-dependent study of TPF-2TPA reveals the involvement of a structural relaxation during ICT state formation. The present study sheds light on the rational design of unconventional ICT chromophores based on fluoranthene, thereby widening the applications of fluoranthene-based molecular systems in optoelectronic devices.Item Open Access Manganese oxide-based mesoporous thin-film electrodes: manganese disproportionation reaction in alkaline media(Royal Society of Chemistry, 2024-02-01) Karakaya Durukan, Irmak; Ulu, Işıl; Dağ, ÖmerIn this study, we explore the disproportionation reaction mechanism in alkaline media during the oxygen evolution reaction (OER) utilizing mesoporous electrodes, namely LiMn2O4 (m-LMO), Mn3O4 (m-Mn3O4), and Mn2P2O7 (m-MnPP). The electrodes are crafted through the molten salt-assisted self-assembly (MASA) process. The procedure commences with the application of a metal salt(s)–surfactant and metal salt–pyrophosphoric acid–surfactant (where the surfactant is P123) lyotropic liquid crystalline mesophase coating over a FTO surface by employing a clear ethanol or aqueous solution of the ingredients, followed by a subsequent calcination step at 300 °C. The electrodes are characterized by spectroscopic, diffraction, imaging, and electrochemical techniques. At low electrochemical potentials, Mn(III), and at more positive potentials, Mn(VI) disproportionation reactions make these materials highly unstable in alkaline media. The aforementioned degradation processes have been investigated by examination of the electrodes both prior to and after subsequent use in electrochemical measurements in various electrolytes. We found that the degradation process is relatively slow in m-LMO, but elevated in m-Mn3O4 and m-MnPP electrodes. m-LMO is fully converted into the λ-MnO2 phase upon its oxidation and more robust to decomposition; making it ultra-thin further improves its robustness. However, the m-Mn3O4 and m-MnPP electrodes behave similarly to each other and degrade more quickly (more pronounced in the latter), by releasing purple-colored permanganate ions into the electrolyte media. A Mn(VI) disproportionation reaction mechanism is suggested using the experimentally gathered spectroscopic, diffraction, and electrochemical data. The formation of Mn(VI) surface species and their electronegativity play vital roles in the disproportionation reaction.Item Open Access Polystyrene-supported catalysts(CRC Press, LLC, 2024-07-26) Phul, Ruby; Khokhar, Deepali; Kour, Manjinder; Sharma, Alpesh Kumar; Jadoun, SapanaRecent development of sustainable synthetic procedures and green technologies are vital for progressing the quality of living. With the limited availability of resources, significance of recyclable catalysts become more promising in the era of climate crisis. Apart from inorganic catalysts, polymer-supported catalysts have gained considerable attention possessing properties like inertness, non-volatility, non-toxicity, reusability, and insolubility which offers an easy synthetic path, materials availability, and higher efficiency. Amongst polymeric support, the polystyrene-based catalyst support is extensively employed as intermediates in various organic synthesis reactions, namely allylboration of aldehydes, epoxidation of alkenes, and various cross-coupling reactions that are sustainable and provident. This book chapter focuses on various polystyrene-based support catalyst and their uses in organic synthesis, pharmaceuticals, and chemical industries.Item Open Access Synthesis of acenaphthylene-fused heteroarenes and polyoxygenated benzo[j]fluoranthenes via a pd-catalyzed Suzuki-Miyaura/C-H arylation cascade(Beilstein-Institut, 2024-12-23) Yence, Merve; Ahmadli, Dilgam; Sürmeli, Damla; Karacaoğlu, Umut Mert; Pal, Sujit; Türkmen, Yunus EmreAcenaphthylene-fused heteroarenes with a variety of five- and six-membered heterocycles such as thiophene, furan, benzofuran, pyrazole, pyridine and pyrimidine were synthesized via an efficient Pd-catalyzed reaction cascade in good to high yields (45-90%). This cascade involves an initial Suzuki-Miyaura cross-coupling reaction between 1,8-dihalonaphthalenes and heteroarylboronic acids or esters, followed by an intramolecular C-H arylation under the same conditions to yield the final heterocyclic fluoranthene analogues. The method was further employed to access polyoxygenated benzo[j]fluoranthenes, which are all structurally relevant to benzo[j]fluoranthene-based fungal natural products. The effectiveness of our strategy was demonstrated via a concise, four-step synthesis of the tetramethoxybenzo[j]fluoranthene derivative 18 , which represents a formal total synthesis of the fungal natural product bulgarein.Item Unknown Overcoming instability challenges of binder-free, self-standing 1T-TiS2 electrodes in aqueous symmetric supercapacitors through dopamine functionalization(ELSEVIER, 2025-03) Koçak, Yusuf; Ülgüt, Burak; Özensoy, Emrah; Uçar, Ali Deniz; Bağlıcakoğlu, Sümeyye Kandur; Durukan, Mete Batuhan; Cugunlar, Murathan; Öz, Sena; Ünalan, Hüsnü EmrahTwo-dimensional materials draw considerable interest for energy storage. Semimetallic phases of transition metal dichalcogenides (TMDs), notably titanium disulfide (TiS2), are extensively studied for their distinctive electronic, chemical, and optical traits. TiS2, initially proposed for Li-ion batteries, holds promise for supercapacitors, although its utilization faces stability challenges in aqueous environments. Herein, electrically conducting and surface-passivated 2D 1T-TiS2 flakes were fabricated and tailored for application as electrodes in supercapacitors with enhanced durability. For this purpose, self-standing and flexible 1T-TiS2 films were fabricated using vacuum filtration and treated with dopamine (DA) to obtain electrochemically stable supercapacitor electrodes in aqueous environments. During DA treatment, in-situ generation of hydrogen peroxide (H2O2) leads to the formation of a thin titanium dioxide (TiO2) overlayer on TiS2, enhancing oxidation stability. At a scan rate of 10 mV s−1, a single electrode demonstrated a gravimetric specific capacitance of 128 F g−1, a volumetric specific capacitance of 122 F cm−3, and an areal specific capacitance of 244 mF cm−2. The symmetric supercapacitor device demonstrated an impressive capacity retention of 96.1 % after 10000 cycles and 85.5 % after 18000 cycles. These results pave the way for utilizing 2D 1T-TiS2 in aqueous environments, expanding its possible applications and holding promise for significant advancements in the field.Item Unknown Advanced diagnosis and early warning strategies on degradation and safety of lithium-ion batteries(Frontiers Research Foundation, 2024-06-21) Aydinol, Mehmet Kadri; Ulgut, Burak; Oh, Ki-Yong; Ozturk, TayfurItem Unknown Cyanide linkage isomerization induced by cobalt oxidation-state changes at a Co-Fe prussian-blue analogue/ZnO interface(Wiley-VCH Verlag GmbH & Co. KGaA, 2024-10-28) De, R.; Hermesdorf, M.; Bera, A.; Phul, Ruby; Gawlik, A.; Plentz, J.; Oschatz, M.; Karadaş, Ferdi; Dietzek-Ivansic, B.Understanding the interfacial composition in heterostructures is crucial for tailoring heterogenous electrochemical and photoelectrochemical processes. This work aims to elucidate the structure of a series of Co-Fe Prussian blue analogue modified ZnO (PBA/ZnO) electrodes with interface-sensitive vibrational sum frequency generation (VSFG) spectroscopy. Our measurements revealed, for the first time, a cyanide linkage isomerism at the PBA/ZnO interface, when the composite is fabricated at elevated temperatures. In situ VSFG spectro-electrochemistry measurements correlate the CoII -> CoIII oxidation with the flip of the bridging CN ligand from Co-NC-Fe coordination mode to a Co-CN-Fe one. Photoluminescence measurements and X-ray photoelectron spectroscopy reveal that this unprecedented linkage isomerism originates from surface defects, which act as oxidation sites for the PBA. The presence of such surface defects is correlated with the fabrication temperature for PBA/ZnO. Thus, this contribution identifies the interplay between the surface states of the ZnO substrates and the chemical composition of PBA at the ZnO surface, suggesting an easily accessible approach to control the chemical composition of the interface.Item Unknown A Twist in biphthalimide-based chromophores enables thermally activated delayed fluorescence(American Chemical Society, 2024-04-18) Debnath, S.; Ramkissoon, P.; Vonder Haar, A.L.; Salzner, Ulrike; Smith, T.A.; Musser, A.J.; Patil, S.Thermally activated delayed fluorescence (TADF) emitters, which convert nonemissive triplets into emissive singlets, have garnered tremendous impetus as next-generation organic electroluminescent materials. Employing donor−acceptor (D−A) designs to produce intramolecular charge transfer (ICT) states is considered an attractive strategy to effectively reduce the singlet− triplet (ΔEST) gap, thereby enhancing reverse intersystem crossing (rISC) in TADF emitters. Herein, we report two ICT chromophores (BP-1TPA and BP-2TPA) utilizing a rational design strategy based on a twisted biphthalimide acceptor core integrated with varying triphenylamine donors. We accomplish efficient TADF emission with a high photoluminescence quantum yield (PLQY) of ∼80% at ambient conditions from poly(methyl methacrylate)-doped films of these chromophores. Twisting the acceptor core ensures the separation of natural transition orbitals, leading to small ΔEST and generates an intermediate triplet excited state to facilitate rISC. The present study, therefore, sheds light on how delayed fluorescence can be realized from a simple twisted phthalimide core by rational molecular engineering and enables new insights toward exploring the aromatic imide class of molecules as potential organic light-emitting materials.Item Unknown Breakup amplitudes from the pseudostate extension of the coupled-reaction-channels method(Springer Wien, 2024-03-02) Kuruoğlu, Zeki C.A pseudochannel extension of the coupled-reaction-channel (CRC) ansatz had been used in earlier work to simulate the effect of the breakup channel on the rearrangement amplitudes. Comparisons with benchmark results on model systems established that rearrangement amplitudes and total breakup probability could be obtained accurately.However, achieving the same level of accuracy with respect to the state-to-state breakup amplitudes had eluded the earlier attempts that used global bases to generate the pseudo states.With the global bases it is difficult to control the spectrum of pseudostate energies and to obtain an optimal distribution of these pseudo-levels. In the present work, local bases in momentum space of the type used in Finite Element methods are employed. Pseudostates are generated using a local interpolation basis in the relative momentum of the two-body subsystem. Local nature of such a basis allows us to control the density of two-body pseudostates by simply adjusting the distribution of the grid points. In the present work, it is demonstrated that breakup amplitudes can be extracted quantitatively using pseudostates generated from a basis of local piecewise quadratic interpolation polynomials. For a local-potential s-wave model of the n + d scattering, state-to-state breakup amplitudes obtained from the present approach are compared with the benchmark results available in the literature. Results further confirm that pseudostate-extended CRC method is a viable and efficient approach for three-particle scattering.Item Unknown Probing the interfacial molecular structure of a co-Prussian blue in situ(Wiley-VCH Verlag GmbH & Co. KGaA, 2024-04-29) Bera, A.; De, R.; Schmidt, H.; Leistenschneider, D.; Ulusoy Ghobadi, Türkan Gamze; Oschatz, M.; Karadaş, Ferdi; Dietzek-Ivansic, B.Molecular-level insight into the interfacial composition of electrodes at thesolid-electrolyte and the solid-electrode interface is essential to understandingthe charge transfer processes, which are vital for electrochemical (EC) andphotoelectrochemical (PEC) applications. However, spectroscopic access toboth interfaces, particularly upon application of an external bias, remains achallenge. Here, in situ surface sensitive vibrational sum-frequencygeneration (VSFG) spectroscopy is used for the first time to directly access theinterfacial structure of a cobalt-containing Prussian blue analog (Co-PBA) incontact with the electrolyte and TiO 2 /Au surface. Structural andcompositional changes of the Prussian blue layer during electrochemicaloxidation are studied by monitoring the stretching vibration of the CN group.At open circuit potential, VSFG reveals a non-homogeneous distribution ofoxidation states of metal sites: Fe III –CN–Co II and FeII –CN–Co III coordinationmotifs are dominantly observed at the Co-PBA|TiO 2 interface, while it is onlythe FeII –CN–Co II unit at the electrolyte interface. Upon increasing thepotential applied to the electrode, the partial oxidation of Fe II –CN–Co II toFeIII –CN–Co II is observed followed by its transformation to FeII –CN–Co III viacharge transfer and, finally, the formation of Fe III –CN–Co III species at theinterface with TiO2 and the electrolyte.Item Unknown 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, EmrahMgO, 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.Item 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, FerdiThis 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.Item 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, ÖmerA 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.