Disposition of Iridium on Ruthenium Nanoparticle Supported on Ketjenblack: Enhancement in Electrocatalytic Activity toward the Electrohydrogenation of Toluene to Methylcyclohexane.

Electrohydrogenation of toluene (TL) to methylcyclohexane (MCH) has been recognized as a promising technology for the hydrogenation process in the organic hydride hydrogen storage system. Recently, we found that the Ketjenblack (KB)-supported Ru-Ir alloy electrocatalyst showed a high electrocatalytic activity for the electrohydrogenation of TL to MCH, and there was the synergy of Ir electrocatalysis for the formation of adsorbed hydrogen species (H) (H + e → H) and Ru catalysis for hydrogenation of TL (6H + TL → MCH). In this paper, the Ir-modified Ru nanoparticle supported on KB (Ir/Ru/KB) electrocatalyst was synthesized by using a modified spontaneous deposition method.

Surface-Regulated Nano-SnO2/Pt3Co/C Cathode Catalysts for Polymer Electrolyte Fuel Cells Fabricated by a Selective Electrochemical Sn Deposition Method.

We have achieved significant improvements for the oxygen reduction reaction activity and durability with new SnO2-nanoislands/Pt3Co/C catalysts in 0.1 M HClO4, which were regulated by a strategic fabrication using a new selective electrochemical Sn deposition method. The nano-SnO2/Pt3Co/C catalysts with Pt/Sn = 4/1, 9/1, 11/1, and 15/1 were characterized by STEM-EDS, XRD, XRF, XPS, in situ XAFS, and electrochemical measurements to have a Pt3Co core/Pt skeleton-skin structure decorated with SnO2 nanoislands at the compressive Pt surface with the defects and dislocations.

Same-View Nano-XAFS/STEM-EDS Imagings of Pt Chemical Species in Pt/C Cathode Catalyst Layers of a Polymer Electrolyte Fuel Cell.

We have made the first success in the same-view imagings of 2D nano-XAFS and TEM/STEM-EDS under a humid N2 atmosphere for Pt/C cathode catalyst layers in membrane electrode assemblies (MEAs) of polymer electrolyte fuel cells (PEFCs) with Nafion membrane to examine the degradation of Pt/C cathodes by anode gas exchange cycles (start-up/shut-down simulations of PEFC vehicles). The same-view imaging under the humid N2 atmosphere provided unprecedented spatial information on the distribution of Pt nanoparticles and oxidation states in the Pt/C cathode catalyst layer as well as Nafion ionomer-filled nanoholes of carbon support in the wet MEA, which evidence the origin of the formation of Pt oxidation species and isolated Pt nanoparticles in the nanohole areas of the cathode layer with different Pt/ionomer ratios, relevant to the degradation of PEFC catalysts.

Mapping platinum species in polymer electrolyte fuel cells by spatially resolved XAFS techniques.

There is limited information on the mechanism for platinum oxidation and dissolution in Pt/C cathode catalyst layers of polymer electrolyte fuel cells (PEFCs) under the operating conditions though these issues should be uncovered for the development of next-generation PEFCs. Pt species in Pt/C cathode catalyst layers are mapped by a XAFS (X-ray absorption fine structure) method and by a quick-XAFS(QXAFS) method. Information on the site-preferential oxidation and leaching of Pt cathode nanoparticles around the cathode boundary and the micro-crack in degraded PEFCs is provided, which is relevant to the origin and mechanism of PEFC degradation.

Performance and durability of Pt/C cathode catalysts with different kinds of carbons for polymer electrolyte fuel cells characterized by electrochemical and in situ XAFS techniques.

The electrochemical activity and durability of Pt nanoparticles on different kinds of carbon supports in oxygen reduction reactions (ORR) were investigated using rotating disc electrodes (RDE) and the membrane electrode assemblies (MEA) of polymer electrolyte fuel cells (PEFC). The mass activity of Pt/C catalysts (ORR activity per 1 mg of Pt) at the RDE decreased, according to the type of carbon support, in the following order; Ketjenblack (KB) > acetylene black (AB) > graphene > multiwall carbon nanotube (MW-CNT) > carbon black (CB), whereas the average size of the Pt nanoparticles and the surface specific activity (ORR activity per electrochemical surface area) did not vary significantly between these carbon supports. These results indicate that the different mass activities of the Pt/C catalysts may originate from the differences in the fraction of Pt on the carbon supports which is available for utilization.

Performance and characterization of a Pt-Sn(oxidized)/C cathode catalyst with a SnO2-decorated Pt3Sn nanostructure for oxygen reduction reaction in a polymer electrolyte fuel cell.

We have prepared and characterized a SnO2-decorated Pt-Sn(oxidized)/C cathode catalyst in a polymer electrolyte fuel cell (PEFC). Oxygen reduction reaction (ORR) performance of Pt/C (TEC10E50E) remained almost unchanged or even tended to reduce in repeated I-V load cycles, whereas the I-V load performance of the Pt-Sn(oxidized)/C prepared by controlled oxidation of a Pt-Sn alloy/C sample with the Pt3Sn phase revealed a significant increase with increasing I-V load cycles. The unique increase in the ORR performance of the Pt-Sn(oxidized)/C catalyst was ascribed to a promoting effect of SnO2 nano-islands formed on the surface of Pt3Sn core nanoparticles.

μ-XAFS of a single particle of a practical NiO(x)/Ce2Zr2O(y) catalyst.

μ-XAFS analysis using an X-ray μ-beam (1000 nm (h) × 800 nm (v)) was successfully carried out on a single particle of a practical catalyst NiO(x)/Ce(2)Zr(2)O(y) (0 ≤x≤ 1, 7 ≤y≤ 8). The oxidation state and local coordination structure of the NiO(x)/Ce(2)Zr(2)O(y) particle were characterized by Ni K-edge μ-XANES and μ-EXAFS, which showed the catalytically active and inactive phases of a single catalyst particle.