Browsing by Author "Ulgut, Burak"
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Item Open Access Analysis of errors in zero-free-parameter modeling approach to predict the voltage of electrochemical energy storage systems under arbitrary load(Electrochemical Society, 2017) Ulgut, Burak; Uzundal, Can Berk; Özdemir, ElifIn a recently published article (J. Electrochem. Soc. 164 (2017) A1274-A1280), we described a new method to predict the voltage response of electrochemical energy storage systems during arbitrary load profiles. Our work shows that the impedance spectrum can be employed in the frequency domain in order to ultimately calculate the time domain behavior of the electrochemical energy storage system. The big advantage of this method is the fact that there are no free parameters and fits throughout. The present work deals with the sources of error in the above-mentioned prediction approach and looks for the effects of the various sources of error. The current analysis concludes that two big contributors to the overall error are the inaccuracies in the DC part of the prediction and the non-linearities that are not modeled by a linear impedance spectrum. Discussions are also made regarding ways to improve the performance of the modeling approach the most and where future work is going to be looking to improve.Item Open Access Application of the kramers–kronig relations to multi-sine electrochemical impedance measurements(Institute of Physics Publishing, 2020) You, C.; Zabara, Mohammed Ahmed; Orazem, M. E.; Ulgut, BurakImpedance spectra obtained by fast Fourier transformation of the response to a multi-sine potential perturbation are shown to be consistent with the Kramers–Kronig relations, even for systems that are nonlinear and nonstationary. These results, observed for measurements on a Li/SOCl2 battery, were confirmed by numerical simulations. Consistency with the Kramers–Kronig relations was confirmed by use of the measurement model developed by Agrawal et al. and by a linear measurement model approach developed by Boukamp and implemented by Gamry. The present work demonstrates that application of the Kramers–Kronig relations to the results of multi-sine measurements cannot be used to determine whether the experimental system satisfies the conditions of linearity, causality and stability.Item Embargo Assessing local electrical properties of ionic liquid/metal interfaces with Operando-XPS and by incorporating additional circuit elements(ACS Publications, 2023-10-10) Karaoğlu, Gözde; Kutbay, Ezgi; İnce, Süleyman; Ulgut, Burak; Süzer, ŞefikX-ray photoelectron spectroscopy (XPS) has been utilized to record binding energy changes upon applying direct current (DC) and/or alternating current (AC) (square-wave) bias with different frequencies on a coplanar capacitor, having an ionic liquid (IL) film as the electrolyte. Electrical potential developments in numerous locations on the device are extracted from the variations in binding energy positions of the atomic core levels, which together with electrochemical measurements are used to extract local information before and after insertion of additional resistors in series. The presence of the IL introduces complex charging/discharging processes with a direct influence on the electrical double layer (EDL) formation, some of which can be untangled from each other via AC modulation by choosing appropriate time windows of observation. Accordingly, under 10 kHz modulation, fast processes are sampled, which are associated with electronic currents, and effects of slow migratory currents can be measured using 0.1 Hz. The addition of serial resistors allows us to quantify AC currents passing through, which reveals the magnitude of the system’s impedance under different conditions. This process surprisingly reverses differences(s) in the voltage developments between the low and high frequencies over the electrified electrodes compared to those over the porous membrane in between. Our approach turns XPS into a powerful electrical and surface-sensitive tool for extracting localized electrochemical properties in a noninvasive and direct way. We expect that a wider utilization of the technique will lead to better identification of the obstacles for developing the next-generation sensing, energy harvesting, and storage systems as well as devices for iontronic/neuromorphic applications. © 2023 American Chemical Society.Item Embargo Battery chemistry prediction with short measurements and a decision tree algorithm: Sorting for a proper recycling process(Elsevier, 2023-06-28) Karaoğlu, Gözde; Ulgut, BurakGiven the push for electrification in every front, the demand for batteries is going to keep increasing. The current rates of growth for production of raw materials are not expected to keep up with this increasing demand. Therefore, recycling has to be a significant part of the value chain in providing the raw materials. Presorting the batteries collected prior to a recycling operation would greatly improve the efficiency of the process. Given users of consumer batteries cannot classify their spent batteries by their chemistries, a chemistry identification will need to be implemented at the industrial scale. We are reporting on a decision tree that is based on a density measurement along with electrical measurements in order to classify batteries by their chemistry in addition to a provision for reusability. 109 batteries are measured in total from a battery recycling bin, including batteries from commercial retailers that were used for various applications.Item Open Access DC electrowetting of nonaqueous liquid revisited by XPS(American Chemical Society, 2018) Aydoğan-Göktürk, Pınar; Ulgut, Burak; Süzer, ŞefikLiquid poly(ethylene glycol) (molecular weight, ∼600 Da) with a low vapor pressure is used as droplets in an ultrahigh-vacuum X-ray photoelectron spectrometer (XPS) chamber with traditional electrowetting on dielectric (EWOD) device geometry. We demonstrate that, using XPS data, independent of the sign of the applied voltage, the droplet expands on the substrate with the application of a nonzero voltage and contracts back when the voltage is brought back to zero. However, the main focus of the present investigation is about tracing the electrical potential developments on and around the droplet, using the shifts in the binding energy positions of the core levels representative of the liquid and/or the substrate in an noninvasive and chemically specific fashion, under imposed electrical fields, with an aim of shedding light on numerous models employed for simulating EWOD phenomenon, as well as on certain properties of liquid/solid interfaces. While the lateral resolution of XPS does not permit to interrogate the interface directly, we explicitly show that critical information can be extracted by probing both sides of the interface simultaneously under external bias in the form of potential steps or direct current. We find that, even though no potential drop is observed at the metal-wire electrode/liquid interface, the entire potential drop develops across the liquid/solid-substrate interface, which is faster than our probe time window (∼100 ms) and is promptly complying with the applied bias until breakdown. No indication of band bending nor additional broadening can be observed in the C 1s peak of the liquid, even under electrical field strengths exceeding 107 V/m. Moreover and surprisingly, the liquid recovers within seconds after each catastrophic breakdown. All of these findings are new and expected to contribute significantly to a better understanding of certain physicochemical properties of liquid/solid interfaces.Item Open Access Electrochemical Impedance Spectroscopy based voltage modeling of lithium Thionyl Chloride (Li∖SOCl2) primary battery at arbitrary discharge(Elsevier, 2020-02) Zabara, Mohammed Ahmed; Ulgut, BurakPrimary batteries possess high energy densities that is beneficial to numerous important applications where recharging is impossible or impractical. The ability to accurately predict the voltage behavior of the battery under certain discharge regime is crucial in battery selection. In this work, Electrochemical Impedance Spectroscopy based approach is applied to predict the voltage of Lithium Thionyl Chloride (Li/SOCl2) primary battery under two discharge conditions. The predicted voltage responses show high accuracy with minor deviations related to the passivation phenomena at the anode. Relevant corrections were made to improve the accuracy of the simulated voltages. The modeling method shows accurate voltage predictions at all states of charge. Moreover, the method was used to predict the voltage of Lithium Manganese Dioxide (Li/MnO2) primary battery. The results show decent match with the experimental values demonstrating the applicability of the method to other chemistries of primary batteries.Item Open Access Electrochemical noise analysis in batteries(Elsevier, 2022-12-10) Karaoğlu, Gözde; Hatipoğlu, Gizem; Ulgut, BurakElectrochemical noise is invaluable in the investigations of stochastic electrochemical processes. Though historically it has been applied almost exclusively to crevice and pitting corrosion studies, application to batteries is interesting for basic science and shows a huge potential for non-perturbing real-time sensor development. Given this promise, noise studies on batteries are starting to appear in the literature. In this manuscript, we are going to critically evaluate the small but emerging body of literature and investigate the mathematical methods employed. We will discuss the intricacies of electrochemical noise applied to batteries both in measurements and in analysis in order to initiate a deeper discussion. In conclusion, we argue that reliance on mathematical methods alone is not the answer, as all mathematical methods use require parameters to guide the analysis. Instead, post-mortem characterizations of batteries can guide the understanding of noise signals measured in batteries, guiding potential mathematical analysis methods and their steps.Item Open Access Electrolyte screening studies for Li metal batteries(Royal Society of Chemistry, 2020-08) Seok, J.; Zhang, N.; Ulgut, Burak; Jin, A.; Yu, S.-H.; Abruna, H. D.From 60 solvent electrolyte combinations tested, we find that Li metal anodes, tested in 1 M LiFSI in DOL:DME exhibit an outstanding cycling performance (>500 cycles) even at high current densities (3 mA cm−2). The excellent performance is ascribed, at least in part, to a low Li nucleation overpotential and a low charge transfer resistance during cycling.Item 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, ÖmerThe 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.Item Open Access In situ XPS reveals voltage driven asymmetric ion movement of an ionic liquid through the pores of a multilayer graphene electrode(American Chemical Society, 2018) Çamcı, Merve Taner; Ulgut, Burak; Kocabaş,Coşkun; Süzer, ŞefikUnder application of a voltage bias, asymmetric ion movement of an ionic liquid (IL) through a multilayered graphene (MLG) electrode has been detected by X-ray photoelectron spectroscopy, via recording the intensity of the two nitrogen peaks. Accordingly, we observe that upon increasing the bias, the two peaks representing the cationic and anionic fragments of the IL start appearing with increasing intensity, together with an asymmetry in their ratio, differing from unity by about 10%. Bias-dependent binding energy shifts followed through atomic features of the IL (F 1s, N 1s, and C 1s) and the graphene electrode (C 1s) indicate that a distinct solid-liquid interface develops throughout the entire intercalation process with an additional and pertinent evidence for finite potential drops across the two electrical double layers. This evidence is bolstered by the fact that the measured binding energy difference between the F 1s of the liquid and C 1s peak of the semisolid MLG electrode is only about half of the applied bias, where the rest of the applied voltage is screened by the two electrical double layers at the solid-liquid interfaces between (i) the MLG-IL and (ii) IL-bottom metal electrode. A simple electrostatic estimation indicates that even this small 10% ion imbalance would lead to 4 orders of magnitude larger voltage development between the IL and the MLG phases and suggests the need for amendment(s) to the current understanding of the dielectric description of ILs.Item Embargo 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 EmreItem 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, ÖmerItem Open Access Method for visualizing under-coating corrosion utilizing pH indicators before visible damage(Elsevier B.V., 2018) Uzundal, C. B.; Ulgut, BurakA new method for under-coating corrosion visualization is developed. The method detects corrosion through local pH gradients which are visualized by pH indicators. pH gradients are induced in a setup similar to the one popularized by Devanathan. On the uncoated back side of the metal, the sample is cathodically polarized, generating hydrogen gas through electrolysis. The hydrogen generated, diffuses through the metal sample and oxidizes on the anodically polarized painted side wherever the coating develops a defect causing a decrease in the local pH. The local pH is then used in imaging the location of defects through the use of a pH indicator, before any visible corrosion damage occurs on the coated metal sample.Item Open Access Modification of mesoporous LiMn2O4 and LiMn2−xCoxO4 by SILAR method for highly efficient water oxidation electrocatalysis(Wiley, 2020-06) Karakaya, Irmak; Karadaş, Ferdi; Ulgut, Burak; Dağ, ÖmerIridium, ruthenium, and cobalt oxides are target materials as efficient and stable mesoporous metal oxide electrocatalysts for oxygen evolution reaction (OER). However, they are costly, toxic, and not practical for an efficient OER process. Here, a two‐step method is introduced, based on earth‐abundant manganese; molten salt‐assisted self‐assembly process to prepare mesoporous LiMn2−xCoxO4 (x = 0–0.5) modified electrodes, in which a systematic incorporation of Co(II) into the structure is performed using successive ionic layer adsorption and reaction followed by an annealing (SILAR‐AN) process. Applying SILAR‐AN over a stable m‐LiMn1.6Co0.4O4 electrode improves the OER performance; the Tafel slope and overpotential drop from 66 to 46 mV dec−1 and 304 to 265 mV (at 1.0 mA cm−2), respectively. The performance of the modified electrodes is comparable to benchmark IrO2 and RuO2 catalysts and much better than cobalt oxide electrodes. Electronic interactions between the neighboring Mn and Co sites synergistically amplify the OER performance of the m‐LiMn2−xCoxO4 electrodes. The data are compatible with an eight steps nucleophilic acid‐base reaction mechanism during OER.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.Item Open Access Nanoengineering InP quantum dot-based photoactive biointerfaces for optical control of neurons(Frontiers Media S.A., 2021-06-23) Karatum, O.; Aria, M. M.; Eren, G. Ö.; Yıldız, E.; Melikov, R.; Srivastava, S. B.; Sürme, S.; Bakış Doğru, I.; Jalali, H. B.; Ulgut, Burak; Şahin, A.; Kavaklı, İ. H.; Nizamoğlu, S.Light-activated biointerfaces provide a non-genetic route for effective control of neural activity. InP quantum dots (QDs) have a high potential for such biomedical applications due to their uniquely tunable electronic properties, photostability, toxic-heavy-metal-free content, heterostructuring, and solution-processing ability. However, the effect of QD nanostructure and biointerface architecture on the photoelectrical cellular interfacing remained unexplored. Here, we unravel the control of the photoelectrical response of InP QD-based biointerfaces via nanoengineering from QD to device-level. At QD level, thin ZnS shell growth (∼0.65 nm) enhances the current level of biointerfaces over an order of magnitude with respect to only InP core QDs. At device-level, band alignment engineering allows for the bidirectional photoelectrochemical current generation, which enables light-induced temporally precise and rapidly reversible action potential generation and hyperpolarization on primary hippocampal neurons. Our findings show that nanoengineering QD-based biointerfaces hold great promise for next-generation neurostimulation devices.Item Embargo On the use of drift correction for electrochemical impedance spectroscopy measurements(Elsevier, 2023-02-01) Orazem, M.E.; Ulgut, BurakThe 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.Item Open Access RuO2 supercapacitor enables flexible, safe, and efficient optoelectronic neural interface(Wiley-VCH Verlag GmbH & Co. KGaA, 2022-08-01) Karatum, O.; Yildiz, E.; Kaleli, H. N.; Sahin, A.; Ulgut, Burak; Nizamoglu, S.Optoelectronic biointerfaces offer a wireless and nongenetic neurostimulation pathway with high spatiotemporal resolution. Fabrication of low-cost and flexible optoelectronic biointerfaces that have high photogenerated charge injection densities and clinically usable cell stimulation mechanism is critical for rendering this technology useful for ubiquitous biomedical applications. Here, supercapacitor technology is combined with flexible organic optoelectronics by integrating RuO2 into a donor–acceptor photovoltaic device architecture that facilitates efficient and safe photostimulation of neurons. Remarkably, high interfacial capacitance of RuO2 resulting from reversible redox reactions leads to more than an order-of-magnitude increase in the safe stimulation mechanism of capacitive charge transfer. The RuO2-enhanced photoelectrical response activates voltage-gated sodium channels of hippocampal neurons and elicits repetitive, low-light intensity, and high-success rate firing of action potentials. Double-layer capacitance together with RuO2-induced reversible faradaic reactions provide a safe stimulation pathway, which is verified via intracellular oxidative stress measurements. All-solution-processed RuO2-based biointerfaces are flexible, biocompatible, and robust under harsh aging conditions, showing great promise for building safe and highly light-sensitive next-generation neural interfaces.