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To improve the electrical conductivity in the Ba2In2O5 (BIO) system without a large volume change from room temperature to 1273 K, BIO materials dually doped with Zr4+ and Zn2+ samples were prepared by using a soft chemical method. Ba2(In0.7,(Zn0.5,Zr0.5)0.3)2O5 (BIZZO-0.3) consists of an orthorhombic phase from room temperature to 1273 K. While phase transformation with a large volume change was not observed for BIZZO-0.3 in the aforementioned temperature region, the electrical conductivity observed for BIZZO-0.3 was higher than the disordered state of BIO when the measurement temperature of conductivity was more than 923 K. The effect of multiple doping on the enhancement of electrical conductivity was characterized by using the transmission electron microscopy (TEM) analysis. Also, the aforementioned effect was discussed in relation to the atomistic simulation result to explain the TEM observation results. The combination of XRD phase analysis, TEM observation and atomistic simulation indicates that a Frenkel defect cluster (i.e. ) was formed in the ordered state of the BIO lattice. It is concluded that the formation of the Frenkel defect cluster in the BIO lattice contributes to the promotion of local disordering of oxygen vacancies at the microscopic scale and maximization of electrical conductivity in the BIO system.

A design paradigm for fabrication of high quality thermoelectric material was demonstrated by using wurtzite ZnO based materials. To prepare the three-dimensional stacking faults in the microstructure of ZnO, Ga2O3 and In2O3 which were guided by atomistic simulation were selected as doping oxides in wurtzite ZnO. TEM microanalysis experimentally confirmed two kinds of stacking faults which were along the basal-plane (i.e. {0001}) and pyramidal-plane (i.e. {10–14}) in the microstructure of ZnO dually doped with small amount of Ga2O3 and In2O3. Also, EDS analysis results indicated the dopant segregation effect at stacking faults which was predicted by our atomistic simulation results. By varying doping levels, it was found that the (Ga0.004, In0.004)Zn0.992O with dense three-dimensional stacking faults revealed low lattice thermal conductivity (1.7 W m−1 K−1 at 773 K) and high thermo-electric performance (ZT: 0.19 at 773 K) in the present work. Based on all experimental results, it is expected that the combined method of atomistic simulation, microanalysis and processing route design will provide us great opportunity for design of three-dimensional stacking faults in the microstructure of ZnO with high performance.

In situ electrochemical X-ray absorption fine structure (XAFS) measurements were performed at the Pt L3 and Ce L3 edges of the Pt–CeOx/C catalyst, which was prepared by a combined process of precipitation and coimpregnation methods, as well as at the Pt L3 edge of the conventional Pt/C catalyst in oxygen-saturated H2SO4 solution to clarify the role of CeOx in the reduction of the overpotential for the oxygen reduction reaction (ORR) at the Pt–CeOx nanocomposite compared with the conventional Pt/C catalyst. XAFS measurements clearly show that the enhancement of ORR activity is attributed to the inhibition of Pt oxide formation by the CeOx layer, of which Ce3+ was oxidized to Ce4+ instead of Pt at the Pt oxide formation potential.

Pt-CeOx/C (1.5

Pt on ceria (CeOx) particles supported on carbon black (CB) were synthesized using the combined process of hot precipitation and impregnation methods. During 30 cycles of cyclic voltammetry pre-treatment in the potential ranging from −0.2 to 1.3 V (V vs. Ag/AgCl), it was observed that a small amount of CeOx, which consisted of the interface region between Pt and CeOx, remained on Pt particles. Other free CeOx particles were dissolved into H2SO4 aqueous solution. To develop the Pt-CeOx/CB catalyst, the surface chemical states, the net chemical composition, morphology and electrochemical behavior in H2SO4 aqueous solution were characterized. Our microanalysis and electrochemical analysis indicate that the active CeO2 with high specific surface area provides the continuous amorphous cerium oxide (Ce3+ ,C e 4+) layer with pores on the surface of Pt particles. It is concluded that the amorphous cerium oxide layer on Pt inhibits the oxidation of Pt surface and contributes to enhancement of the activity on Pt cathode. The single cell performance was also improved using the Pt-CeOx/CB cathode. Based on all data, it is expected that the design based on characterization of the interface between Pt and small amount of amorphous cerium oxide layer could help in preparation of more active Pt catalyst.

Pt-CeOx/C (1.5 ≤ x ≤ 2) electro-catalyst is one of the most promising cathode materials for use in polymer membrane electrolyte fuel cells. To clarify the microstructure of Pt-CeOx heterointerface, we prepared Pt-loaded CeOx thin film on conductive SrTiO3 single crystal substrate by using a stepwise process of pulse laser deposition method for the preparation of epitaxial growth CeOx film followed by an impregnation method which loaded the Pt particles on the CeOx film. The electrochemistry observed for the Pt-loaded CeOx thin film on the conductive single crystal substrate was examined by using cyclic voltammetry in 0.5 M H2SO4 aqueous solution, and a cross-sectional image of the aforementioned Pt-CeOx thin film electrode was observed using a transmission electron microscope. The electrochemistry observed for Pt-CeOx thin film electrode clearly showed the promotion effect of CeOx. Also, the microanalysis indicated that unique, large clusters that consisted of C-type rare-earth-like structures were formed in the Pt-CeOx interface by a strong interaction between Pt and CeOx. The present combination analysis of the electrochemistry, microanalysis, and atomistic simulation indicates that the large clusters (i.e., 12 (PtCe''-Vo(••)) + 2 (PtCe''-2Vo(••)-2CeCe')) that were formed into the Pt-CeOx interface promoted the charge transfer between Pt surface and CeOx, suggesting that the oxygen reduction reaction activity on Pt can be maximized by fabrication of C-type rare-earth-like structure that consists of the aforementioned large clusters in the Pt-CeOx interfaces.

Pt-CeO(x)/C electrocatalysts for the improvement of oxygen reduction reaction (ORR) activity on cathode were prepared by a combined process of precipitation and co-impregnation methods. The Pt-CeO(x)/C electrocatalysts pretreated by the optimized electrochemical conditioning process showed high ORR activity as compared with homemade Pt/C electrocatalyst. Also, it showed high stability in the cyclic voltammetry (CV) test up to 1000 cycles into 0.5 M H(2)SO(4) aqueous solution. On the basis of the data of cyclic voltammogram of 30 cyclic sweeps, X-ray photoelectron spectroscopy, electron energy loss spectroscopy, high resolution transmission electron microscope image, and selected area electron diffraction analysis, it is concluded that the Pt-CeO(x) heterointerface involving the defect cluster formed by using optimized electrochemical pretreatment conditions on Pt in Pt-CeO(x)/C electro-catalyst contributes to the promotion of ORR activity and retention of its stability in long CV tests up to 1000 cycles.

Pt-CeOx interface on Pt electrodes was prepared for improvement of both oxygen reduction reaction (ORR) activity of Pt cathode and CO tolerance of Pt anode. The surface of Pt-CeOx nano-particle/C electrode mainly consists of metallic Pt, ionized Pt (i.e. Pt2+) and Ce3+ species. The ORR activity on Pt was improved by the formation of Pt-CeOx interface. In-situ XAFS analysis suggests that cerium oxide surface in the Pt-CeOx/C was oxidized instead of Pt surface by electrochemical redox reaction of CeOx at room temperature. This suggests that the Pt-CeOx interface plays key role for improvement of cathode performance. Also, CO tolerance of Pt was improved by the formation of aforementioned interface. The improvement of CO tolerance of Pt was also observed by using in-situ IR analysis. Based on all experimental data, it is concluded that the design of defect structure in Pt-CeOx provides us opportunity to make the breakthrough electrodes for fuel cell application.

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The oxygen reduction reaction (ORR) is one of the important reactions not only in life processes but also in artificial energy conversion systems, such as fuel cells and metal/air batteries. As one of the non-precious ORR catalysts, N-doped carbon materials show an exciting activity, but most of them were universally synthesized by high-temperature pyrolysis or annealing up to 1100 °C in the past few decades, which makes the structural manipulation of the catalysts extremely difficult. Here, we propose that ORR active N-doped carbon catalysts could, in principle, be prepared via a sophisticated wet chemical reaction between a reactive graphitic carbon template (e.g. graphene oxide) and N-containing molecules (e.g. dicyandiamide) at temperatures as low as 180 °C. Without any high-temperature treatments, for example, the as-prepared N-doped reduced graphene oxide with additional Fe-containing nanoparticles showed an impressive ORR catalytic activity that was comparable to many previous N-doped carbon from high-temperature pyrolysis. Rational utilization of the graphitic carbon template, the N-containing molecules, and the wet chemical reactions may offer a low-temperature route to create interesting ORR electrocatalysts with easier surface properties manipulation.