Browsing by Subject "Synthetic metals"

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Open Access
Continuous mesoporous pd films by electrochemical deposition in nonionic micellar solution
(American Chemical Society, 2017) Iqbal, M.; Li C.; Wood, K.; Jiang B.; Takei, T.; Dag, Ö.; Baba, D.; Nugraha, A. S.; Asahi, T.; Whitten, A. E.; Hossain, M. S. A.; Malgras, V.; Yamauchi, Y.
Mesoporous metals that combine catalytic activity and high surface area can provide more opportunities for electrochemical applications. Various synthetic methods, including hard and soft templating, have been developed to prepare mesoporous/nanoporous metals. Micelle assembly, typically involved in soft-templates, is flexible and convenient for such purposes. It is, however, difficult to control, and the ordering is significantly destroyed during the metal deposition process, which is detrimental when it comes to designing precisely mesostructured materials. In the present work, mesoporous Pd films were uniformly electrodeposited using a nonionic surfactant, triblock copolymer poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide), as a pore-directing agent. The interaction between micelles and metal precursors greatly influences the metal growth and determines the final structure. The water-coordinated species interact with the ethylene oxide moiety of the micelles to effectively drive the Pd(II) species toward the working electrode surface. From small-angle neutron scattering data, it is found that spherical P123 micelles, with an average diameter of ∼14 nm, are formed in the electrolyte, and the addition of Pd ions does not significantly modify their structure, which is the essence of the micelle assembly approach. The uniformly sized mesopores are formed over the entire mesoporous Pd film and have an average pore diameter of 10.9 nm. Cross-sectional observation of the film also shows mesopores spanning continuously from the bottom to the top of the film. The crystallinity, crystal phase, and electronic coordination state of the Pd film are also confirmed. Through this study, it is found that the optimized surfactant concentration and applied deposition potential are the key factors to govern the formation of homogeneous and well-distributed pores over the entire film. Interestingly, the as-prepared mesoporous Pd films exhibit superior electrocatalytic activity toward the ethanol oxidation reaction by fully utilizing the accessible active surface area. Our approach combines electrochemistry with colloidal and coordination chemistry and is widely applicable to other promising metals and alloy electrocatalysts.
Open Access
Does the donor-acceptor concept work for designing synthetic metals? 2. theoretical investigation of copolymers of 4-(dicyanomethylene)-4H-cyclopenta[2, 1-b: 3, 4-b′]dithiophene and 3, 4-(ethylenedioxy)thiophene
(American Chemical Society, 2002) Salzner, U.; Köse, M. E.
Density functional theory (DFT) calculations were performed on oligomers of 3,4-(ethylenedioxy)thiophene (EDOT), 4-(dicyanomethylene)-4H-cyclopenta[2,1-b:3,4-b′]dithiophene (CDM), and co-oligomers (CDM/ EDOT). Oligomer data were extrapolated to polymer values. Theoretical band gaps reproduce λmax from UV spectroscopy for PEDOT and are about 1 eV larger than electrochemical band gaps. λmax of PCDM/EDOT is predicted to be 0.42 eV smaller than that of PEDOT and 0.15 eV smaller than that of PCDM. PCDM/EDOT has a wide valence and an extremely narrow conduction "band". It is probably better not to refer to these localized states as a band at all. This rationalizes the mobility ratio of 500 between p-type and n-type charge carriers and the low n-type conductivity of PCDM/EDOT. The lack of dispersion of the conduction band is due to the very different EAs of EDOT and CDM.