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  • 1. Das, Suman
    et al.
    Swain, Diptikanta
    Araujo, Rafael B.
    Shi, Songxin
    Ahuja, Rajeev
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics. Uppsala University, Sweden.
    Row, Tayur N. Guru
    Bhattacharyya, Aninda J.
    Alloying in an Intercalation Host: Metal Titanium Niobates as Anodes for Rechargeable Alkali-Ion Batteries2018In: Chemistry - An Asian Journal, ISSN 1861-4728, E-ISSN 1861-471X, Vol. 13, no 3, p. 299-310Article in journal (Refereed)
    Abstract [en]

    We discuss here a unique flexible non-carbonaceous layered host, namely, metal titanium niobates (M-Ti-niobate, M: Al3+, Pb2+, Sb3+, Ba2+, Mg2+), which can synergistically store both lithium ions and sodium ions via a simultaneous intercalation and alloying mechanisms. M-Ti-niobate is formed by ion exchange of the K+ ions, which are specifically located inside galleries between the layers formed by edge and corner sharing TiO6 and NbO6 octahedral units in the sol-gel synthesized potassium titanium niobate (KTiNbO5). Drastic volume changes (approximately 300-400%) typically associated with an alloying mechanism of storage are completely tackled chemically by the unique chemical composition and structure of the M-Ti-niobates. The free space between the adjustable Ti/Nb octahedral layers easily accommodates the volume changes. Due to the presence of an optimum amount of multivalent alloying metal ions (50-75% of total K+) in the M-Ti-niobate, an efficient alloying reaction takes place directly with ions and completely eliminates any form of mechanical degradation of the electroactive particles. The M-Ti-niobate can be cycled over a wide voltage range (as low as 0.01V) and displays remarkably stable Li+ and Na+ ion cyclability (>2 Li+/Na+ per formula unit) for widely varying current densities over few hundreds to thousands of successive cycles. The simultaneous intercalation and alloying storage mechanisms is also studied within the density functional theory (DFT) framework. DFT expectedly shows a very small variation in the volume of Al-titanium niobate following lithium alloying. Moreover, the theoretical investigations also conclusively support the occurrence of the alloying process of Li ions with the Al ions along with the intercalation process during discharge. The M-Ti-niobates studied here demonstrate a paradigm shift in chemical design of electrodes and will pave the way for the development of a multitude of improved electrodes for different battery chemistries.

  • 2. Li, Fei
    et al.
    Yu, Fengshou
    Du, Jian
    Wang, Yong
    Zhu, Yong
    Li, Xiaona
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. Dalian University of Technology, China.
    Water Splitting via Decoupled Photocatalytic Water Oxidation and Electrochemical Proton Reduction Mediated by Electron-Coupled-Proton Buffer2017In: Chemistry - An Asian Journal, ISSN 1861-4728, E-ISSN 1861-471X, Vol. 12, no 20, p. 2666-2669Article in journal (Refereed)
    Abstract [en]

    Water splitting mediated by electron-coupled-proton buffer (ECPB) provides an efficient way to avoid gas mixing by separating oxygen evolution from hydrogen evolution in space and time. Though electrochemical and photoelectrochemcial water oxidation have been incorporated in such a two-step water splitting system, alternative ways to reduce the cost and energy input for decoupling two half-reactions are desired. Herein, we show the feasibility of photocatalytic oxygen evolution in a powder system with BiVO4 as a photocatalyst and polyoxometalate H3PMo12O40 as an electron and proton acceptor. The resulting reaction mixture was allowed to be directly used for the subsequent hydrogen evolution with the reduced H3PMo12O40 as electron and proton donors. Our system exhibits excellent stability in repeated oxygen and hydrogen evolution, which brings considerable convenience to decoupled water splitting.

  • 3. Li, Zhong-Yu
    et al.
    Wu, Wenjun
    Zhang, Qiong
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Jin, Bin
    Hua, Jianli
    Yang, Hai-Bo
    Tian, He
    Restricted Rotation of sigma-Bonds through a Rigidified Donor Structure to Increase the ICT Ability of Platinum-Acetylide-Based DSSCs2013In: Chemistry - An Asian Journal, ISSN 1861-4728, E-ISSN 1861-471X, Vol. 8, no 11, p. 2660-2669Article in journal (Refereed)
    Abstract [en]

    A series of new triarylamine-based platinum-acetylide complexes (WYs) have been designed and synthesized as new sensitizers for applications in dye-sensitized solar cells (DSSCs). With the aim of investigating the effect of a rigidifying donor structure on the photoelectrical parameters of the corresponding DSSCs, two new sensitizers, WY1 and WY2, with rigid and coplanar fluorene units as an electron donor, were prepared. Moreover, two sensitizers that contained triphenylamine units as an electron donor, WY3 and WY4, were also synthesized for comparison. The photo- and electrochemical properties of all of these new complexes have been extensively explored. We found that the dimethyl-fluorene unit exhibited a stronger electron-donating ability and better photovoltaic performance compared to the triphenylamine unit, owing to its rigidifying structure, which restricted the rotation of sigma bonds, thus increasing the conjugation efficiency. Furthermore, WY2, which contained a dimethyl-fluorene unit as an electron donor and bithiophene as a bridge, showed a relatively high open-circuit voltage (V-oc) of 640mV and a PCE of 4.09%. This work has not only expanded the choice of platinum-acetylide sensitizers, but also demonstrates the advantages of restricted rotation of donor sigma bonds for improved behavior of the corresponding DSSCs.

  • 4.
    Liu, Tianqi
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry.
    Zhang, Biaobiao
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry.
    Sun, Licheng
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry.
    Iron-Based Molecular Water Oxidation Catalysts: Abundant, Cheap, and Promising2019In: Chemistry - An Asian Journal, ISSN 1861-4728, E-ISSN 1861-471X, Vol. 14, no 1, p. 31-43Article, review/survey (Refereed)
    Abstract [en]

    An efficient and robust water oxidation catalyst based on abundant and cheap materials is the key to converting solar energy into fuels through artificial photosynthesis for the future of humans. The development of molecular water oxidation catalysts (MWOCs) is a smart way to achieve promising catalytic activity, thanks to the clear structures and catalytic mechanisms of molecular catalysts. Efficient MWOCs based on noble-metal complexes, for example, ruthenium and iridium, have been well developed over the last 30 years; however, the development of earth-abundant metal-based MWOCs is very limited and still challenging. Herein, the promising prospect of iron-based MWOCs is highlighted, with a comprehensive summary of previously reported studies and future research focus in this area.

  • 5. Ren, Bo
    et al.
    Dong, Hai
    Ramström, Olof
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    A Carbohydrate- Anion Recognition System in Aprotic Solvents2014In: Chemistry - An Asian Journal, ISSN 1861-4728, E-ISSN 1861-471X, Vol. 9, no 5, p. 1298-1304Article in journal (Refereed)
    Abstract [en]

    A carbohydrate-anion recognition system in nonpolar solvents is reported, in which complexes form at the B-faces of -D-pyranosides with H1-, H3-, and H5-cis patterns similar to carbohydrate- interactions. The complexation effect was evaluated for a range of carbohydrate structures; it resulted in either 1:1 carbohydrate-anion complexes, or 1:2 complex formation depending on the protection pattern of the carbohydrate. The interaction was also evaluated with different anions and solvents. In both cases it resulted in significant binding differences. The results indicate that complexation originates from van der Waals interactions or weak CHA(-) hydrogen bonds between the binding partners and is related to electron-withdrawing groups of the carbohydrates as well as increased hydrogen-bond-accepting capability of the anions.

  • 6. Wu, ZhiFang
    et al.
    Li, Xin
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Li, Jing
    Hua, JianLi
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Tian, He
    Influence of the Auxiliary Acceptor on the Absorption Response and Photovoltaic Performance of Dye-Sensitized Solar Cells2014In: Chemistry - An Asian Journal, ISSN 1861-4728, E-ISSN 1861-471X, Vol. 9, no 12, p. 3549-3557Article in journal (Refereed)
    Abstract [en]

    Three new dyes with a 2-(1,1-dicyanomethylene)rhodanine (IDR-I, -II, -III) electron acceptor as anchor were synthesized and applied to dye-sensitized solar cells. We varied the bridging molecule to fine tune the electronic and optical properties of the dyes. It was demonstrated that incorporation of auxiliary acceptors effectively increased the molar extinction coefficient and extended the absorption spectra to the near-infrared (NIR) region. Introduction of 2,1,3-benzothiadiazole (BTD) improved the performance by nearly 50%. The best performance of the dye-sensitized solar cells (DSSCs) based on IDR-II reached 8.53% (short-circuit current density (J(sc))=16.73mAcm(-2), open-circuit voltage (V-oc)=0.71V, fill factor (FF)=71.26%) at AM1.5 simulated sunlight. However, substitution of BTD with a group that featured the more strongly electron-withdrawing thiadiazolo[3,4-c]pyridine (PT) had a negative effect on the photovoltaic performance, in which IDR-III-based DSSCs showed the lowest efficiency of 4.02%. We speculate that the stronger auxiliary acceptor acts as an electron trap, which might result in fast combination or hamper the electron transfer from donor to acceptor. This inference was confirmed by electrical impedance analysis and theoretical computations. Theoretical analysis indicates that the LUMO of IDR-III is mainly localized at the central acceptor group owing to its strong electron-withdrawing character, which might in turn trap the electron or hamper the electron transfer from donor to acceptor, thereby finally decreasing the efficiency of electron injection into a TiO2 semiconductor. This result inspired us to select moderated auxiliary acceptors to improve the performance in our further study.

  • 7.
    Xie, Sheng
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry. College of Chemistry and Chemical Engineering, Hunan University, Changsha, 410082, China.
    Manuguri, Sesha
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry.
    Ramström, Olof
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry. University of Massachusetts Lowell, 1 University Ave., Lowell, MA 01854, United States.
    Yan, Mingdi
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry. University of Massachusetts Lowell, 1 University Ave., Lowell, MA 01854, United States.
    Impact of Hydrogen Bonding on the Fluorescence of N-Amidinated Fluoroquinolone2019In: Chemistry - An Asian Journal, ISSN 1861-4728, E-ISSN 1861-471X, Vol. 14, no 6, p. 910-916Article in journal (Refereed)
    Abstract [en]

    The fluorescence properties of AIE-active N-amidinated fluoroquinolones, efficiently obtained by a perfluoroaryl azide-aldehyde-amine reaction, have been studied. The fluorophores were discovered to elicit a highly sensitive fluorescence quenching response towards guest molecules with hydrogen-bond-donating ability. This effect was evaluated in a range of protic/aprotic solvents with different H-bonding capabilities, and also in aqueous media. The influence of acid/base was furthermore addressed. The hydrogen-bonding interactions were studied by IR, NMR, UV/Vis and time-resolved fluorescence decay, revealing their roles in quenching of the fluorescence emission. Due to the pronounced quenching property of water, the N-amidinated fluoroquinolones could be utilized as fluorescent probes for quantifying trace amount of water in organic solvents.

  • 8. Zhang, B.
    et al.
    Wu, X.
    Li, F.
    Yu, F.
    Wang, Y.
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. Dalian University of Technology (DUT), China.
    In Situ Formation of Efficient Cobalt-Based Water Oxidation Catalysts from Co2+-Containing Tungstate and Molybdate Solutions2015In: Chemistry - An Asian Journal, ISSN 1861-4728, E-ISSN 1861-471X, Vol. 10, no 10, p. 2228-2233Article in journal (Refereed)
    Abstract [en]

    Replacing rare and expensive noble-metal catalysts with inexpensive and earth-abundant ones is of great importance to split water either electrochemically or photoelectrochemically. In this study, two amorphous cobalt oxide catalysts (Co-W film and Co-Mo film) with high activity for electrocatalytic water oxidation were prepared by fast, simple electrodeposition from aqueous solutions of Na<inf>2</inf>WO<inf>4</inf> and Na<inf>2</inf>MoO<inf>4</inf> containing Co2+. In solutions of Na<inf>2</inf>WO<inf>4</inf> and Na<inf>2</inf>MoO<inf>4</inf>, sustained anodic current densities up to 1.45 and 0.95mA cm-2 were obtained for Co-W film at 1.87V versus a reversible hydrogen electrode (RHE) and Co-Mo film on fluorine-doped tin oxide (FTO) substrates at 1.85V versus RHE. For the Co-W film, a much higher current density of 4.5mA cm-2 was acquired by using a stainless-steel mesh as the electrode substrate. Significantly, in long-term electrolysis for 13h, the Co-W film exhibited improved stability in cobalt-free buffer solution in comparison with the previously reported Co-Pi film.

  • 9. Zhang, Biaobiao
    et al.
    Li, Fei
    Yu, Fengshou
    Cui, Honghua
    Zhou, Xu
    Li, Hua
    Wang, Yong
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Homogeneous Oxidation of Water by Iron Complexes with Macrocyclic Ligands2014In: Chemistry - An Asian Journal, ISSN 1861-4728, E-ISSN 1861-471X, Vol. 9, no 6, p. 1515-1518Article in journal (Refereed)
    Abstract [en]

    The activity of eleven separated iron complexes and nine in situ-generated iron complexes towards catalytic water oxidation have been examined in aqueous solutions with Ce(NH4)(2)(NO3)(6) as the oxidant. Two iron complexes bearing tridentate and tetradentate macrocyclic ligands were found to be novel water oxidation catalysts. The one with tetradentate ligand exhibited a promising activity with a turnover number of 65 for oxygen evolution.

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