Masato Machida

Efficient catalytic decomposition of sulfuric acid with copper vanadates as an oxygen-generating reaction for solar thermochemical water splitting cycles

Copper pyrovanadate (Cu(2)V(2)O(7)) was found for the first time to achieve the high catalytic activity for the decomposition of sulfuric acid to evolve O(2) at moderate temperatures around 650 °C, which is essential for the development of solar thermochemical water splitting cycles.

An exploration of nitrate concentrations in groundwater aquifers of central-west region of Bangladesh

Groundwater and river water samples were collected from the study area to investigate the spatial distribution of nitrate (NO(3)(-)) in the central-west region of Bangladesh. The shallow and deep groundwater nitrate concentrations ranged from <0.10 to 75.12 and <0.10 to 40.78 mg/L, respectively. Major river water NO(3)(-) concentrations were ranged from 0.98 to 2.32 mg/L with an average of 1.8 mg/L. The average Cl(-)/NO(3)(-) ratio (4.9) of major river water has been considered as reference point to delineate denitrification processes. The alluvial fan, alluvial, deltaic and coastal deposits shallow groundwater having C1(-)/NO(3)(-) values less than that of the average river water value (4.9), suggested denitrification processes within the aquifers. On the other hand, denitrification processes are insignificant in the Pleistocene terraces area aquifers related to relatively higher concentrations of nitrate. Iron pyrite has been found as insignificant effect on denitrification.

Hydrothermal Synthesis of a Doped Mn‐Cd‐S Solid Solution as a Visible‐Light‐Driven Photocatalyst for H2 Evolution

The effect of metal doping (i.e., with Cr, Fe, Ni, Cu, Zn, Ag and Sn) on the crystal structure of hydrothermally synthesized Mn(1-x)Cd(x) S (where x≈0.1) is studied with the aim of enhancing photocatalytic activity. In contrast to the low-crystalline, undoped solid solution Mn(1-x)Cd(x)S, Ni doping yields a well-crystallized wurtzite-type Mn-Cd-S solid solution, which precipitates as planar hexagonal facets of several hundred nanometers in size, together with much larger grains of α-MnS (>10 μm). By removing inactive α-MnS through sedimentation, a single phase with composition of Ni(0.01)Mn(0.56)Cd(0.43)S is obtained successfully. The Ni doping achieved a threefold higher photocatalytic activity for H(2) evolution from a 0.1 M Na(2)S/0.5 M Na(2)SO(3) solution under visible-light irradiation (λ≥420 nm). The apparent quantum yield of 1 wt % Pt-loaded Ni(0.01)Mn(0.56)Cd(0.43)S measured at λ=420 nm reached 25 %. The enhanced photocatalytic activity is most likely the result of a decreased concentration of defects, responsible for electron-hole recombination, in the active solid-solution phase and a slightly higher bandgap energy (2.4 eV).

Novel oxygen storage mechanism based on redox of sulfur in lanthanum oxysulfate/oxysulfide

A sulfur redox cycle between La(2)O(2)SO(4)(S(6+)) and La(2)O(2)S(S(2-)) phases was found for the first time to achieve the oxygen storage of 2 mol O(2) mol(-1), which is eight times larger than that of the conventional CeO(2)-ZrO(2) system.

Dynamic Behavior of Rh Species in Rh/Al2O3 Model Catalyst during Three-Way Catalytic Reaction: An Operando X-ray Absorption Spectroscopy Study

The dynamic behavior of Rh species in 1 wt% Rh/Al2O3 catalyst during the three-way catalytic reaction was examined using a micro gas chromatograph, a NOx meter, a quadrupole mass spectrometer, and time-resolved quick X-ray absorption spectroscopy (XAS) measurements at a public beamline for XAS, BL01B1 at SPring-8, operando. The combined data suggest different surface rearrangement behavior, random reduction processes, and autocatalytic oxidation processes of Rh species when the gas is switched from a reductive to an oxidative atmosphere and vice versa. This study demonstrates an implementation of a powerful operando XAS system for heterogeneous catalytic reactions and its importance for understanding the dynamic behavior of active metal species of catalysts.

Thermal Evolution of the Structure and Activity of Rh Overlayer Catalysts Prepared by Pulsed Arc-Plasma Deposition

Nanometric Rh overlayers were formed on Fe–Cr–Al stainless steel (SUS) foils by pulsed cathodic arc-plasma (AP) technique to investigate the thermal evolution of the structure and catalytic activity for stoichiometric NO–CO–C3H6–O2 reaction. As-prepared Rh overlayer catalysts (Rh/SUS) with 2000–8000 AP pulsing showed steep light-off of NO, CO and C3H6 at around 250 °C and their conversions soon reached to almost 100%. After thermal aging at 900 °C in H2O/air, however, the catalytic activity was decreased to the different extent depending on the number of AP pulsing. The most significant deactivation was observed for the smallest numbers of AP pulsing (2000), because Al in the foil was oxidized during the aging to form a passivation layer of α-Al2O3, which covered the surface of the foil and decreased the surface concentration of Rh. To overcome this deactivation, the Rh overlayer was formed by AP after preheating the foil at 1000 °C in air. This modified preparation process enables the deposition of Rh overlayer on the highly crystalline α-Al2O3 layer at the surface of the foil, which is found to be much more stable against thermal deactivation.

Catalytic NO–CO–C3H6–O2 reactions over hydrothermally stable Rh-supported ZrP2O7 catalyst

A novel and facile hydrothermal synthetic route for ZrP2O7 from ZrO(OH)2 and H3PO4 has been developed to use this as an active support for Rh catalyst. Temperature-programmed reactions of mixtures of NO, CO, C3H6 and O2 with a stoichiometric A/F ratio (14.6) were investigated over Rh-supported ZrP2O7 catalyst. A lower amount of Rh (0.4 wt.%) loaded to ZrP2O7 exhibited satisfactory light-off at lower temperature (T50% = 312 °C) with a steep rise in conversion efficiency after ageing the catalyst at 900 °C for 25 h in a stream of 10% H2O/air. Rh particle growth was not so significant even after 500 h of ageing at 900 °C in the stream of 10% H2O/air, which is one of the reasons for exhibiting adequate catalytic activity of this catalyst after long-term exposure in H2O/air. Reducibility of Rh oxide was enhanced substantially by this support which is believed to be the key factor for exhibiting good catalytic activity after ageing in an oxidizing environment. This newly developed Rh/ZrP2O7 catalyst with minimum Rh loading, having high thermal stability up to 1200 °C along with outstanding capacity to resist sintering at high temperature, has the potential to serve as a new generation deNOx catalyst.

The Catalysis Society of Japan (CATSJ): History and Activities†

The Catalysis Society of Japan has entered into the 50th anniversary of the foundation in 2008. In celebration of the Golden Jubilee year of the Society, we organized an International Symposium on Creation and Control of Advanced Selective Catalysis in Kyoto. The Symposium was also organized as a PreSymposium of the 14th International Congress on Catalysis in Seoul. The Symposium was the greatest event among several programs for the celebration that the Society has planned. We are very much grateful to so many scientists and engineers for their attendance at the Symposium in Kyoto. The five topics included in the Symposium, namely fundamentals and theory for selective catalysis, in situ characterization of selective catalysis, new selective catalysis for green processes, new catalytic materials for selective catalysis, and innovative processes by selective catalysis, are the key issues and materials to solve the increasing scientific and technological demands in the fields related to the Symposium title, which are believed to be at the frontiers and cutting edge of catalytic science and technology. The excellent class of the invited speakers and the large number of first-class contributed presentations, including highlighted achievements of worldwide young scientists, made up a scientific program that we were truly proud of, and excellent peer-reviewed works are published in this Special Issue of Angewandte Chemie and also in a Special Issue of Topics in Catalysis. Catalysis can play a pivotal role as a central science and technology in ensuring sustainable human life. The theme of the present Symposium is most appropriate, and we found great achievements and new horizons in the papers presented, which will give rise to further developments of the science and technology and will also provide a strong influence to the promotion of the welfare of mankind. We are deeply grateful for financial aid made by the Ministry of Education, Culture, Sports, Science, and Technology (MEXT), Japan Society for the Promotion of Science (JSPS), Commemorative Organization for the Japan World Exposition (1970), and several enterprises. We also wish to express our

Decomposition of Pt-intercalated hydrotalcite-like nanocomposites to produce micro/mesoporous catalysts.

Platinum intercalated into a hydrotalcite-like solid, Mg0.74Al0.26(OH)2(NO3)0.26, was found to catalytically reduce interlayer nitrate (NO3-) to N2/N2O so as to give rise to a large surface area micro/mesoporous structure at lower temperature of ca. 300 degrees C, compared to 500 degrees C required for the decomposition of the pristine hydrotalcite phase.