Kagoshima University · College of Science and Engineering, School of Science · 教授

Research keywords環境影響評価・Environmental Influence Accessment・Geochemistry・Refining and Identification・Separation・の・と・を

Research fieldsChemistry・Stratigraphy/Paleontology・Environmental dynamic analysis・Environmental science・分離・精製・検出法・地球化学・Earth and planetary science・地球科学

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• Kanzaki R., Hidaka T., Tajima S., Kodamatani H., Tomiyasu T. . The “pH-window” of a representative deep eutectic solvent and evaluation of electrodes for pH measurement . Chemical Phys2025 · 記述言語： 日本語 出版者・発行元： Chemical Physics Letters The Brønsted acid–base properties of ethaline, composed of choline chloride and ethylene glycol, were investigated as a representative deep eutectic solvent (DES). Rigorous potentiometric titrations with a hydrogen electrode were performed for the first time in DES to determine the autoprotolysis constant and the p K <inf>a</inf> values of some weak acids. These results revealed a ∼ 4 unit shift in pH relative to water and established the pH window of the DES, which allows direct conversion of the pH value between the DES and conventional solvents. IS-FET and glass electrodes were also evaluated, confirming practical applicability. DOI： 10.1016/j.cplett.2025.142475 Scopus
• Kanzaki R., Hidaka T., Kodamatani H., Tomiyasu T., Fujii K. . Proton-transfer reaction thermodynamics in highly concentrated electrolytes for advanced aqueous lithium-ion batteries . J2025 · 記述言語： 英語 掲載種別： 研究論文（学術雑誌） 出版者・発行元： Journal of Molecular Liquids We have studied proton-transfer reactions in highly concentrated aqueous electrolytes focusing on lithium bis(trifluoromethanesulfonyl)amide (LiTf2N) for potential applications in advanced aqueous lithium-ion batteries. In 20 mol kg−1 LiTf2N aqueous solution, the autoprotolysis constant pKW increased significantly to 16.2, indicating a reduction in ionization compared to bulk water (pKW = 14 at infinite dilution), and the H+ concentration is lower than in dilute aqueous solutions. This was mainly attributed to the increase in the activity coefficient of H+ (γH) with increasing LiTf2N concentration. Calorimetric measurements revealed that the increase in pKW is driven by an increase in the autoprotolysis enthalpy, suggesting that H+ is enthalpically unfavorable in concentrated LiTf2N solutions. In contrast, the autoprotolysis entropy showed no significant contribution to the pKW variation. We extended this study to the acid-base reaction of acetic acid as a model system in highly concentrated electrolyte solutions. The pKa value of acetic acid (or the corresponding ionization Gibbs energy) showed little dependence on the LiTf2N concentration. In contrast, the corresponding ionization enthalpy and entropy increased significantly with increasing LiTf2N concentration. Due to the enthalpy–entropy compensation effect, the pKa value resulted in limited variation even under highly concentrated conditions. The obtained enthalpy values for the ionization processes support that proton carriers lie in an enthalpically unstable state. These findings provide new insights into the fundamental behavior of protons in highly concentrated aqueous electrolytes, which is critical for the design and optimization of aqueous lithium-ion batteries and other electrochemical systems. DOI： 10.1016/j.molliq.2025.127388 Scopus
• Kanzaki R., Hidaka T., Tokuda Y., Kodamatani H., Tomiyasu T. . Brønsted acidity of bis(trifluoromethanesulfonyl)amide and trifluoromethanesulfonic acid in ionic liquids of ternary ammonium2024 · 記述言語： 日本語 出版者・発行元： Journal of Molecular Liquids Bis(trifluoromethanesulfonyl)amide (Tf2N−) and triflate (TfO−) are commonly used anions of protic ionic liquids (PILs). They are the conjugate anions of strong acids, Tf2NH and TfOH, whose Brønsted acidities crucially influence the performance of the PILs. In this study, the Brønsted acidity of Tf2NH and TfOH was compared directly through potentiometric titrations carried out in the ionic liquids of ternary ammonium salts. As a result, Tf2NH exhibits stronger Brønsted acidity than TfOH by approximately 2 pH units. Furthermore, calorimetric titrations revealed that this difference originates from differences in their entropy states. This suggests that the solvation state, rather than the properties in their isolated state, has a more significant impact on the acidities of Tf2NH and TfOH. Besides, ionization thermodynamics turned out to be governed by both the constituent cations and anions of the PILs. Therefore, once the acid-base natures of the constituent ions are characterized, the overall acid-base behavior of the PIL may become predictable. DOI： 10.1016/j.molliq.2024.125433 Scopus
• Kanzaki R., Hidaka T., Kodamatani H., Tomiyasu T. . Determination of autoprotolysis (autoionization) constant according to gran's procedure on potentiometric titrations . Journal of Mo2023 · 記述言語： 日本語 出版者・発行元： Journal of Molecular Liquids Gran's plot is an ingenious tool to find endpoints in potentiometric neutralization titrations. It can also be utilized for determining the formal potential of the electrodes, which is required in the case of obtaining the hydrogen ion concentration with pH sensor electrodes involving glass electrodes. Furthermore, autoprotolysis constants can be determined through Gran's plots with high accuracy, even those containing impurities. Gran's plot is thus a fundamental technique for investigating the properties of novel solvents such as protic ionic liquids as acid-base media. However, there are limitations in the autoprotolysis constants of the solvents and the ionization constants of the impurities, and so on, where Gran's plots work well. Hence, we have clarified the reliable range of these constants to be determined through Gran's plot by calculating the titration curves under various conditions and simulating these determination processes. DOI： 10.1016/j.molliq.2023.122180 Scopus

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