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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>
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,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>
Daisuke Gunji,Takehiro Imura,Hiroshi Fujimoto 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6
In order to improve motion control performance of electric vehicles (EVs), In-Wheel Motor (IWM) is the most preferred electric motor arrangement. Our research group has proposed Wireless In-Wheel Motor (W-IWM) concept to solve some technical problems of an IWM, which are reliability and safety issues of power and signal wires. In this research, we did a stability analysis of Series-Series compensated wireless power transfer via magnetic resonance coupling with constant power load. Analysis result is verified by circuit simulation. Also, we propose a load voltage control method using a secondary converter. The effectiveness of the proposed control method has been verified by simulation and experiment using small power test equipment.
Tomoaki Okuda,Yuma Gunji,Kebin He,Yongliang Ma 한국대기환경학회 2013 Asian Journal of Atmospheric Environment (AJAE) Vol.7 No.3
Measurement of the phosphorus concentration in aerosols in Beijing, which was a representative East Asian mega-city, was carried out. The optimum procedure for analyzing phosphorus in aerosols was found in this study. Recovery of phosphorus in environmental samples through the improved method was almost 100%. The concentration of phosphorus in TSP was 145±47 ng/m3, with a seasonal variation showing high concentrations in winter and low concentrations in summer. The concentrations of phosphorus in PM2.5 accounted for 35±6% of those in TSP, with no seasonal variations. The major source of phosphorus in aerosols in Beijing was soil dust,and additional sources of phosphorus in fine particles could be coal combustion and biomass burning.
Okuda, Tomoaki,Yoshida, Tetsuro,Gunji, Yuma,Okahisa, Shunichi,Kusdianto, K.,Gen, Masao,Sato, Seiichi,Lenggoro, I. Wuled Korean Society for Atmospheric Environment 2015 Asian Journal of Atmospheric Environment (AJAE) Vol.9 No.2
This study focused on the measurement of the actual charging state of ambient aerosol particles, which is important for understanding the intricate process of adverse health effects caused by particulate matter (PM). The net electrostatic charging state of $PM_{2.5}$ collected on filter media was measured in this study. The Faraday cage method and surface potential measurements were used in this study. The results showed that the polarities of the net charging state measured using these two methods were in agreement for 42 out of 48 samples (87.5%), and 36 samples (75%) were negatively charged. The filters were not significantly charged by friction between the filters and air not containing PM. Charge addition to or leakage from the filters was not observed over a two-month storage period. Net charging state of $PM_{2.5}$ collected on the filters was concluded to be negative in most cases, based on data's support of the assumption that aerosol charging state is not altered by the process of PM collection using filter.
Tomoaki Okuda,Tetsuro Yoshida,Yuma Gunji,Shunichi Okahisa,K. Kusdianto,Masao Gen,Seiichi Sato,I. Wuled Lenggoro 한국대기환경학회 2015 Asian Journal of Atmospheric Environment (AJAE) Vol.9 No.2
This study focused on the measurement of the actual charging state of ambient aerosol particles, which is important for understanding the intricate process of adverse health effects caused by particulate matter (PM). The net electrostatic charging state of PM2.5 collected on filter media was measured in this study. The Faraday cage method and surface potential measurements were used in this study. The results showed that the polarities of the net charging state measured using these two methods were in agreement for 42 out of 48 samples (87.5%), and 36 samples (75%) were negatively charged. The filters were not significantly charged by friction between the filters and air not containing PM. Charge addition to or leakage from the filters was not observed over a two-month storage period. Net charging state of PM2.5 collected on the filters was concluded to be negative in most cases, based on data’s support of the assumption that aerosol charging state is not altered by the process of PM collection using filter.