Catalytic performance and QXAFS analysis of Ni catalysts modified with Pd for oxidative steam reforming of methane

Pd–Ni bimetallic catalysts prepared by co-impregnation and sequential impregnation methods were compared in the catalytic performance in oxidative steam reforming of methane. The sequential impregnation was more effective to the suppression of hot spot formation. According to the structural analysis by in situ quick-scanning X-ray absorption fine structure (QXAFS) during the temperature programmed reduction, the sequential impregnation method gave the bimetallic particles with higher Pd surface composition because of the low possibility of the Pd–Ni bond formation. Higher surface composition of Pd with higher reducibility than Ni is connected to the enhancement of the catalyst reducibility and the suppression of the hot spot formation.     

The importance of Fe loading on the N2O reduction with NH3 over Fe-MFI: Effect of acid site formation on Fe species

Effect of the loading amount of Fe over ion-exchanged Fe-MFI catalysts on the catalytic performance of N₂O reduction with NH₃ was investigated, and the results indicated that the turnover frequency (TOF) was almost constant in the Fe/Al range between 0.05 and 0.40. The activity of N₂O + NH₃ reaction was much lower than that of N₂O + CH₄ reaction over Fe-MFI (Fe/Al = 0.40), and the preadsorption of NH₃ decreased drastically the activity of N₂O + CH₄ reaction. The temperature-programmed desorption (TPD) of NH₃ showed the formation of stronger acid sites on Fe-MFI (Fe/Al = 0.24 and 0.40), and the amount of the acid sites agrees well with the desorption amount O₂ in O₂-TPD in the low temperature range. The acid sites gave a 3610 cm⁻¹ peak (Brønsted acid) in FTIR observation. These results suggest that the acid sites were formed on the bridge oxide ions in binuclear Fe species. Adsorbed NH₃ on the strong acid sites inhibited N₂O dissociation, which can be related to the low activity of N₂O + NH₃ reaction over Fe-MFI with high Fe loading.     

Catalytic Performance of Metal Nanoparticles Supported by Ceramic Composite Produced by Partial Reduction of Solid Solution with Dopant

A composite with well-dispersed metal nanoparticles at a ceramic surface was produced by partial reduction of solid solution. It was found that a small amount of dopant, such as Al₂O₃, Cr₂O₃, or Sc₂O₃, accelerated the precipitation of the metal nanoparticles during the reduction. Catalytic performance of the composite for methanol reforming was evaluated. In the Ni-based catalysts, the dopant decreased the CO production by promoting a methanation reaction, while in the Co-based catalysts, the dopant did it by inducing a water–gas shift reaction. Co/MgO with Sc₂O₃ doping showed the most preferable reforming performance, high H₂ production, and CO₂ selectivity.     

Vortex Pinning/Dynamics in YBCO Films with Jc (77 K) > 3·106 A/cm2 Studied by Direct Transport Measurements

Critical current density, J _c , is studied for highly biaxially-oriented YBCO thin films with J _c (77 K) > 3 MA/cm ² in a range of magnetic fields, temperatures, angles between magnetic field vector and film c-axis. J _c (H, ) is shown to be dominated by vortex interaction with high density (> 10 ¹¹ lines/cm ² ) of linear pins — edge dislocations. A model is developed to describe different vortex arrays behavior in the presence of two-dimensional square network of linear pins.     

Dual-Metal Interbonding as the Chemical Facilitator for Single-Atom Dispersions

Atomically dispersed catalysts, with maximized atom utilization of expensive metal components and relatively stable ligand structures, offer high reactivity and selectivity. However, the formation of atomic-scale metals without aggregation remains a formidable challenge due to thermodynamic stabilization driving forces. Here, a top-down process is presented that starts from iron nanoparticles, using dual-metal interbonds (Rh Fe bonding) as a chemical facilitator to spontaneously convert Fe nanoparticles to single atoms at low temperatures. The presence of Rh Fe bonding between adjacent Fe and Rh single atoms contributes to the thermodynamic stability, which facilitates the stripping of a single Fe atom from the Fe nanoparticles, leading to the stabilized single atom. The dual single-atom Rh–Fe catalyst renders excellent electrocatalytic performance for the hydrogen evolution reaction in an acidic electrolyte. This discovery of dual-metal interbonding as a chemical facilitator paves a novel route for atomic dispersion of chemical metals and the design of efficient catalysts at the atomic scale.     

Flow control of NaCl aqueous solution using gas-liquid interface deformation induced by magnetic fields: influence of flow velocity and concentration

The flow control of NaCl aqueous solution was examined by applying gas-liquid interface deformation induced by magnetic fields. Detailed studies of the dependence of flow velocity and concentration on the change in flow rate were carried out. In this experiment, with a flow on the order of 100 ml/min, the change in flow rate was measured under magnetic fields of up to 10 T. The flow rate decreased due to gas-liquid interface deformation at magnetic fields of about 6 T or more; the decrease in flow rate was approximately 23% at most. The change in flow rate was dependent on the flow velocity but not on the concentration. In addition, the possibility of using gas-liquid interface deformation induced by magnetic fields as a new means of controlling the flow of NaCl solution without contact was discussed.     

Diffusion mechanisms for the growth of Nb3Sn intermetallic layers

The analysis of compound formation in a diffusion couple previously developed by the authors has been extended to include the effect of interface kinetics. When interface kinetics dominate, a linear rate law may obtain rather than the parabolic rate law expected if simple bulk diffusion were the rate-limiting process. Additional data for the rate of formation of Nb₃Sn at a bronze-niobium interface have been presented. Our results imply that interface kinetics are important when the concentration of Sn in the bronze matrix exceeds about 8 at.% or when certain metallic impurities are present in the niobium.