Research

Non-Pt cathode catalysts for polymer electrolyte fuel cells (PEFC)

Fuel cell vehicles using PEFCs have been commercialized from Dec. 2014 in Japan and expected to be modern electric
vehicles in the next generation. However, large amount of Pt electrocatalysts is loaded in PEFCsespecially for cathode
electrocatalysts. We have only ca. 200 ton of Pt output in this world and usage of several tens gram of Pt for a passenger car
strongly inhibit the broad spreading. We develop non-Pt electrocatalysts for PEFCs. The polymerelectrolytes of PEFCs are
acidic as strong as diluted sulfuric acid, so that most of inorganic materials are easily
dissolved into the electrolyte exceptprecious metals such as Pt. Then, Pt is widely used for the electrocatalysts in PEFCs.
Although Ta, Nb, Ti, and Zr oxides are known to have extremely high durability in acidic and alkaline media, they are hard to be
electrocatalysts because of lack of electroconductivity. We have found a preparation method of nano-sized Ta, Nb, Ti, and Zr
oxides which have obvious activity for oxygen reduction reaction as cathode electrocatalysts forPEFCs. This technology will be
a key in the hydrogen energy society based on renewable energies.


STEM and TEM images of Ta- and Ti -based nanoparticles for cathode electrocatalysts in PEFCs.		Oxygen reduction current of Nb, Ta, and Zroxidenanopartclesas compared to a commercial Pt catalyst.

In-situ analysis of electrocatalysts of solid oxide fuel cells (SOFC)

SOFCs has been commercialized in residential cogenerationsystems. New model of ENE-FARM, which is ahousecogenerationsystem generating electricity (45% efficiency) and supplying hot water (43% efficiency). Total efficiency reaches 88%, which obviouslyovercomes any large-scale thermal power plant with total energy efficiency from the fuel. One of the advantages of SOFCs is thatthe SOFCs can directly utilize various kinds of fuels such as LNG and syngas without a reforming reactor, but not onlyhydrogen.However, direct use of such carbon based fuels frequently causes carbon deposition on anode electrocatalysts of Ni, so that thecritical control of steam ratio in the fuel is required. Interestingly, the nature of carbondepositionon Ni has been known to bestrongly affected by the kinds of oxide electrolytes, even if the carbon deposition occurs onthe Nisurface.

We study the mechanism of carbon deposition using infrared spectroscopy and reveal the function of electrolytesincarbondeposition. We also study the adsorption sites of oxygen molecules on cathode electrocatalysts of SOFCs such as La-Sr-Mnoxides.


nfrared absorption spectra of adsorbed CO on Ni sites on Ni/ GDC and Ni/YSZ anode electrocatalysts. The properties of adsorbed CO on Ni are different between Ni/GDC and Ni/YSZ.		Schematic image of Ni/GDC surface where GDCspecisearebroadely migrated on Ni surface affecting adsorbedCOon Nisites.

Synthesis of ammonia using electrochemical methods

　Ammoniais one of the bulk chemicals with the production of 18 million tons per year inthe world. More than 80% of ammonia isutilized for fertilizers and supporting our modern agriculture for our foodstuffs in the world. Ammonia can be also used as a fuelwhich can be easily liquefied with elevated pressure. This indicates that ammonia is storable and transportable as liquid phase,which is an advantage over hydrogen fuel. In near future, our society will be installed enough number of renewable-energy powerplants and excess amount of electricity from unstable wind and solar energies will be supplied. Conversion of excess amountofelectricity from unstable renewable energies to chemical fuels is expected to be a key technology in the future society. We studythe technology of ammonia synthesis from air, which consists of water and nitrogen with electrical energy usingselectrochemicalcell. Electrocatalysts for the ammonia electrochemical synthesis is the key componentof the cell.


Electrochemical cells for ammonia production from water and nitrogen.		Time course of electroconductivity of diluted sulfuric acid bubbled with product gasfrom the ammonia synthesis cell (left). The decrease of electroconductivity is due to the neutralization of acid by produced ammonia. Right plot shows ammoniasynthesis rates.

Study of adsorbed species on catalyst surfaces

Any catalytic reaction using solid catalysts takes place on the catalyst surfaces. An adsorbed molecule is the reactionintermediate. Study on the adsorbed molecules on catalyst surfaces is the most fundamental and essential work for understanding the catalysis. Our laboratory is equipped with infrared spectrometers for catalyst surface analysis, temperature-programmed desorption analyzers, pulse laser system for vibrational sum-frequency generation spectroscopy for surface analysis,and scanning tunnel-electron microscopes. These methods clarify the mechanism of catalysis such as explained above.


FTIR spectrometer for observation of adsorbates on catalyst surfaces.		Temperature-programmed desorption spectraofmoleculardioxigen desorbed from cathode catalysts forPEFCs.

Rheological Characteristics of Fine Particles

。 http://www.hosokawamicron.co.jp/jp/product/65		http://www.freemantech.co.uk/_powders/?pt=About the FT4 Page&p=MQ==

Hydrodynamic Charateristics of a Modified Spouted Bed

		Mathur, K.B. and N.Epstein ："Spouted Beds", Academic Press New York (1974) 　ISBN: 9780124800502