A one-pot synthesis of 2,6-dibromodithieno[3,2-b;2',3'-d]thiophene (dibromo-DTT, 4) was developed. A key step was bromodecarboxylation of DTT-2,6-dicarboxylic acid, obtained by saponification of the diester 1. The donor-acceptor dye DAHTDTT (13), based on a central 2,6-bis[2'-(3'-hexylthienyl)]dithieno[3,2-b;2',3'-d]thiophene core (9), was prepared and incorporated in a dye-sensitized solar cell (DSC), which exhibited an energy conversion efficiency of 7.3% with V(oc) of 697 mV, J(sc) of 14.4 mA/cm(2), and ff of 0.73 at 1 sun.
The exothermic behaviour and intrinsic safety of a number of ionic liquids being considered for battery and solar cell applications have been investigated at elevated temperatures by analysing data from accelerated rate calorimetric (ARC) studies.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
In the drive towards efficient and commercially viable dye-sensitised solar cells, there is an increasing requirement for alternative electrolyte materials that can replace the volatile and toxic molecular solvent-based systems. Ionic liquids offer a promising alternative as their non-volatility, good electrical and thermal stability and non-flammability, in addition to the ability to tailor their physical properties through structural manipulation, make them ideal for electrochemical applications. Alternatively, plastic crystals are an attractive solution to the problems of leakage that can be associated with liquid electrolytes. This review discusses the development of these new electrolytes from the perspective of two key parameters; diffusion of the I−/ redox couple through the different materials, and the influence that they can have on the energy levels within the device.
Active and inexpensive catalysts for oxygen reduction are crucially needed for the widespread development of polymer electrolyte fuel cells and metal-air batteries. While iron-nitrogen-carbon materials pyrolytically prepared from ZIF-8, a specific zeolitic imidazolate framework (ZIF) with sodalite topology, have shown enhanced activities toward oxygen reduction in acidic electrolyte, the rational design of sacrificial metal-organic frameworks toward this application has hitherto remained elusive. Here, we report for the first time that the oxygen reduction activity of Fe-N-C catalysts positively correlates with the cavity size and mass-specific pore volume in pristine ZIFs. The high activity of Fe-N-C materials prepared from ZIF-8 could be rationalized, and another ZIF structure leading to even higher activity was identified. In contrast, the ORR activity is mostly unaffected by the ligand chemistry in pristine ZIFs. These structure-property relationships will help identifying novel sacrificial ZIF or porous metal-organic frameworks leading to even more active Fe-N-C catalysts. The findings are of great interest for a broader application of the class of inexpensive metal-nitrogen-carbon catalysts that have shown promising activity also for the hydrogen evolution (Co-N-C) and carbon dioxide reduction (Fe-N-C and Mn-N-C).
Dye-sensitized solar cells are an increasingly promising alternative to conventional silicon solar cells as a method of converting solar energy to electricity and thus providing an effectively inexhaustible energy source. However, the most efficient of these devices currently utilize liquid electrolytes, which suffer from the associated problems of leakage and evaporation. Hence, significant research is currently focused on the development of solid state alternatives. Here we report a new class of solid state electrolyte for these devices, organic ionic plastic crystal electrolytes, that allow relatively rapid diffusion of the redox couple through the matrix, which is critical to the cell performance. A range of different organic ionic plastic crystal materials, utilizing different cation and anion structures, have been investigated and the conductivities, diffusion rates and photovoltaic performance of the electrolytes are reported. The best material, utilizing the dicyanamide anion, achieves efficiencies of more than 5%.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
Electrodeposition of poly(3,4-ethylenedioxythiophene) onto conducting plastic allows the cheap and facile synthesis of plastic cathodes for dye-sensitised solar cells, having excellent solar cell efficiency (8%), at a fraction of the cost of platinised plastic.
While the Proton Exchange Membrane Fuel cell (PEMFC) technology is gradually entering the portable and materials handling vehicle markets, its long term future is subject to further advances in electrocatalysis and to the cost of precious metal catalysts. Today, platinum is used at both the anode and cathode to catalyze the electrochemical reactions, although in much greater amounts in the latter due to the slower Oxygen Reduction Reaction (ORR). Recent non-precious metal catalysts synthesized from a transition metal (Fe, Co), a nitrogen and a carbon precursor have shown unprecedented high activity for the ORR [1-2]. Promising results with metal-free conducting polymers and nitrogen doped carbons have also been reported for catalyzing the ORR in alkaline medium. While metal-free catalysts with high ORR activity in acid medium have been claimed recently, measuring the presence of trace amounts of iron in supposedly metal-free samples is crucial but rarely carried out with experimental techniques that are sensitive enough [3]. The goal of the present work is to assess the role of iron on the ORR activity of MOF derived catalysts and to investigate whether the highest ORR activity observed after NH 3 pyrolysis comes from a true synergetic effect between N-groups and Fe-based centres, or simply comes from the mathematical addition of the intrinsic activity of N-groups on one hand and Fe-based centres on the other hand. The latter hypothesis implies that the ORR activity of such N-groups in acid medium would be commensurate with that of the Fe-based centres, which has never been demonstrated in acid medium so far. In this work, Fe-N-C and N-C catalysts were synthesized by pyrolyzing a commercial ZIF 8 and phenanthroline, with or without addition of iron acetate, respectively. Pyrolysis is performed in Ar, or in Ar and then in NH 3 . The exact Fe contents in the catalysts were measured from the height of the absorption step at Fe K-edge, using X-ray absorption spectroscopy. Various sources of iron contamination for the N-C samples are investigated, such as quartz tube cleanness, pyrolysis gas (NH 3 is a corrosive gas) and C and N precursors (commercial ZIF-8, phenanthroline). Figure 1 shows the polarization curves measured in fuel cell for samples pyrolyzed in Ar (open symbols) or in Ar+NH 3 (filled symbols). Two observations can be made: i) The ORR activity enhancement between samples obtained from 0%Fe/0%phen/MOF and 1%Fe/20%phen/80%MOF is circa 30 after Ar-pyrolysis (open triangle vs open diamond), in relative agreement with Fe bulk contents of ca 0.03 and 3.0 wt %, respectively ii) the same factor is only circa 4 after Ar and NH 3 pyrolysis (filled triangle vs filled diamond), this time in contradiction with the Fe bulk contents of ca 0.07 wt % and 6 wt %, respectively. The high ORR activity of ZIF-8 pyrolyzed first in Ar and then in NH 3 either comes from specific N-groups formed during NH 3 pyrolysis, or from Fe traces present in the commercial MOF or unintentionally added during the synthesis. Several possible sources of Fe traces, such as contaminated quartz tube, ballmilling process, types of gas used for pyrolysis, or purity of the MOF precursor were investigated and will be discussed. [1] E. Proietti, F. Jaouen, M. Lefèvre, N. Larouche, J. Herranz, J. Tian, J.P. Dodelet, Nat. Comm . 2 ( 2011 ) 416 [2] G. Wu, K.L. More, C.M. Johnston, P. Zelenay, Science 332 ( 2011 ) 443 [3] J. Masa, A. Zhao, W. Xia, Z.Sun, B. Mei, M. Muhler, W.Schuhmann, Electrochem. Comm 34 (2013) 113 Figure caption. PEMFC polarisation curves with 4 mg cm -2 of N-C or Fe-N-C catalysts at the cathode, 0.4 mg Pt cm -2 at the anode, Nafion 211 membrane. H 2 and O 2 , 100% RH, 80°C, 1 bar gauge pressure. Figure 1
'/%3e%3c/defs%3e%3cpath fill='%23012169' d='M0 0h10080v5040H0z'/%3e%3cpath stroke='%23fff' stroke-width='.6' d='m0 0 6 3m0-3L0 3' clip-path='url(%23b)' transform='scale(840)'/%3e%3cpath stroke='%23e4002b' stroke-width='.4' d='m0 0 6 3m0-3L0 3' clip-path='url(%23c)' transform='scale(840)'/%3e%3cpath stroke='%23fff' stroke-width='840' d='M2520 0v2520M0 1260h5040'/%3e%3cpath stroke='%23e4002b' stroke-width='504' d='M2520 0v2520M0 1260h5040'/%3e%3cg fill='%23fff'%3e%3cuse xlink:href='%23d' x='2520' y='3780'/%3e%3cuse xlink:href='%23a' x='7560' y='4200'/%3e%3cuse xlink:href='%23a' x='6300' y='2205'/%3e%3cuse xlink:href='%23a' x='7560' y='840'/%3e%3cuse xlink:href='%23a' x='8680' y='1869'/%3e%3cuse xlink:href='%23e' x='8064' y='2730'/%3e%3c/g%3e%3c/svg%3e)
