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Koura, Nobuyuki,Matsuzawa, Hidenori,Kato, Tomoki,Idemoto, Yasushi,Matsumoto, Futoshi The Korean Electrochemical Society 2002 한국전기화학회지 Vol.5 No.4
The structure of species formed in $NbCI_5-I-ethyl-3-methylimidazolium$ chloride (EMIC) room-temperature molten salt (RTMS) was examined with the Raman spectroscopic measurement and ab initio molecular orbital calculation. The equilibrium structures of $NbCl_5,\;NbCl_6^-,\;Nb_2CI_{10},\;Nb_2CI_{11}^-,\;Nb_3CI_6^-,\;NbCI_6^--EMI^+\;(in\;which\;NbCI_6^-$ anion approaches $EMI^+$ cation with strong interaction) and $Nb_2CI_{11}^--EMI^+$ were obtained with the HF/LANL2DZ level of calculation. The harmonic frequencies at each equilibrium structure were compared with Raman spectra. The harmonic frequencies of $NbCI_6^--EMI^+,\; Nb_2CI_{11}^--EMI^+,\;and\;Nb_2CI_{10}$ were in good agreement with the Raman spectra of RTMS melts. In the $NbCI_5-EMIC RTMS$, the main species were $NbCI_6^-\;and\;EMI^+$. In the $NbCl_5-EMIC$ RTMS added $NbCl_5\;over\;50mol\%$, small amount of $Nb_2CI_{11}^-\;and\; Nb_2CI_{10}$ were also formed. The structures of anions and cation in the RTMS distorted from free ions with Coulomb force.
Gunji, Takao,Wakabayashi, Ryo H.,Noh, Seung Hyo,Han, Byungchan,Matsumoto, Futoshi,DiSalvo, Francis J.,Abruñ,a, Hé,ctor D. Elsevier 2018 ELECTROCHIMICA ACTA Vol.283 No.-
<P><B>Abstract</B></P> <P>We present an investigation of the alloying effects of 3d transition metals with palladium, and on their activity towards the oxygen reduction reaction (ORR) in alkaline media, as well as the durability of the electrocatalysts over time. Bimetallic Pd-<I>M</I> (<I>M</I> = Fe, Co and Ni) nanoparticles (NPs) were prepared by an impregnation method followed by reduction under forming gas and a subsequent annealing treatment. In order to enhance the catalytic activity towards the ORR, the bimetallic Pd-<I>M</I> nanoparticles were electrochemically dealloyed. The dealloyed Pd-<I>M</I> nanoparticles had a core-shell structure with a Pd<SUB>3</SUB> <I>M</I>-core and a Pd-shell about 1 nm in thickness. The core-shell materials exhibited higher electrocatalytic activity towards the ORR, and longer-term durability when compared to pure Pd.</P>
Koura, Nobuyuki,Minami, Takuto,Etoh, Keiko,Idemoto, Yasushi,Matsumoto, Futoshi The Korean Electrochemical Society 2002 한국전기화학회지 Vol.5 No.4
The electrochemical behavior of binder-free carbon anode, comprising of only artificial and natural graphite (AG and NG) particles, for intercalation and deintercalation of lithium ion $(Li^+)$ in aluminum chloride (AICI_3)-I-ethyl3-methylimidazolium chloride (EMIC)-lithium chloride (LiCl)-thionyl chloride $(SOCI_2)$ room-temperature molten salt (RTMS) was studied. Binder-free carbon electrodes were fabricated using electrophoretic deposition (EPD) method. The binder-free carbon anodes provided a relatively flat charge and discharge potentials $(0\;to\;0.2V\;vs.\;Li/Li^+)$ and current capabilities $(250-340mAh{\cdot}g^{-1})$ for the intercalation and deintercalation of $Li^+$. Stability of the binder-free carbon anodes for intercalation and deintercalation of 50 cycles was confirmed.
Gunji, Takao,Noh, Seung Hyo,Tanabe, Toyokazu,Han, Byungchan,Nien, Chiao Yin,Ohsaka, Takeo,Matsumoto, Futoshi American Chemical Society 2017 Chemistry of materials Vol.29 No.7
<P>Nanosized ordered intermetallic Pd3Pb nanoparticles (NPs)/carbon black (CB) (1-8 rim), Pd3Pb NPs/CB, in which Pd3Pb has a Cu3Au-type structure and its NPs are supported on CB, were prepared by the polyol method under an air atmosphere and characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM), and X-ray photoelectron spectroscopy (XPS). The XRD and XPS measurements confirmed the formation of ordered intermetallic Pd3Pb NPs with a super lattice phase, and the TEM and STEM images indicated a relatively uniform dispersion of Pd3Pb NPs on the CB surface with an average size of 4.3 nm and an atomic ratio (Pd:Pb) of 75.9:24.1. The surface of the asprepared Pd3Pb NPs/CB was found to be covered with the Pb (and its oxide) layer and to possess actually no electrocatalysis for the electrooxidation of formic acid (FA). However, this 'inactive' asprepared Pd3Pb NPs/CB could be changed drastically to the 'active' one with a high level of electrocatalysis by the electrochemical treatment using cyclic voltammetry, i.e., the pertinent electrooxidation of the Pb surface coating in a 0.1 M HClO4 aqueous solution. The atomicresolution STEM measurements confirmed that the surface state of the 'inactive' asprepared Pd3Pb NPs/CB can be controlled by changing the number of potential scans employed in the electrochemical treatment. That is, when the potential scan number is suitably chosen, the surface covered with the Pb coating dissolves and becomes an active, ideal structure of Pd3Pb, and further scanning leads to a surface close to that of Pd NPs. The thus electrochemically treated ideal Pd3Pb NPs/CB possessed a largely higher level of electrocatalysis for the FA oxidation than Pd NPs/CB, which could be explained reasonably on the basis of the experimentally measured and/or theoretically calculated dband center values of both catalysts and CO binding energies on them.</P>
Gunji, Takao,Noh, Seung Hyo,Ando, Fuma,Tanabe, Toyokazu,Han, Byungchan,Ohsaka, Takeo,Matsumoto, Futoshi The Royal Society of Chemistry 2018 Journal of Materials Chemistry A Vol.6 No.30
<P>A structurally ordered phase of PdCu3 nanoparticles (NPs)/carbon black (CB), in which PdCu3 has a Cu3Au-type structure, was prepared by co-reduction of Pd and Cu precursors using ethylene glycol as a reducing agent and an annealing procedure. The obtained catalysts were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM), energy-dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). The XRD and STEM measurements enabled us to confirm the crystal structures of both atomically disordered Pd-Cu NPs/CB and ordered intermetallic PdCu3 NPs/CB. From the TEM and EDS measurements, it was found that PdCu3 NPs are uniformly dispersed on the CB surface and the atomic ratio of Pd to Cu is 25.3 : 74.7. DFT calculations suggested that the PdCu3 NPs have a uniformly ordered structure of Pd and Cu and that Cu-free surface-structured PdCu3 NPs, which are formed by so-called electrochemical dealloying, <I>i.e.</I>, the dissolution of surface and sub-surface Cu in the ordered PdCu3 structure, exhibit superior electrocatalytic activity in the ORR in comparison with Pd NPs/CB. This catalytic activity can be explained reasonably on the basis of the measured value of the d-band center and theoretical calculations of catalyst-oxygen binding energies. Interestingly, the surface of electrochemically dealloyed PdCu3 has a lower oxygen binding energy than the Pt (111) surface (<I>i.e.</I>, the oxygen binding energy of PdCu3 was significantly decreased by electrochemical dealloying). We have found a Pd-based catalyst of which the electrocatalytic activity in the ORR may exceed that of Pt-based catalysts according to DFT calculations. In addition, the potential of PdCu3 NPs/CB as a cathode catalyst in direct methanol fuel cells is discussed briefly.</P>