The image is a Tokyo Institute of Technology transmission electron microscope (TEM) photo of nano niobium phosphate obtained by adding a chelating agent to niobium oxide and using 5M phosphoric acid. It is a precursor to a more robust polymer fuel cell electrolyte.
Image Source: FIG. 11 from U.S Patent Application 20100009190
Polymer electrolyte fuel cells (PEFC a.k.a. PEMFC) have a high output density and may be manufactured to a small size with a light weight. They are expected to be applied to automobiles, co-generation systems for domestic use, and mobile equipment.
However, for practical use, there is still a great need for further improvement in endurance and performance. To this end, it is necessary to improve the performance of an electrolyte or a catalytic component in a membrane electrode assembly. The search for new fuel cell materials is the subject of an intensive worldwide research effort, involving hundreds of laboratories both private and public, consuming more than $4 billion dollars a year in R&D funds. The search more often than not involves nanomaterials.
One of the candidates for new materials for proton exchange membrane fuel cells (PEMFC) is niobium phosphate (NbOPO4.nH2O). In many cases, niobium phosphate has an amorphous structure and can be crystallized by sintering at an elevated temperature of 1000.degree. C.
Also, niobium phosphate is insoluble in water and shows strong acidity. The excellent catalytic activity of this niobium phosphate is mainly derived from Bronsted acid (Nb--OH and P--OH) and hence is felt to possess a high proton donating capability. It is thus felt that niobium phosphate may be used as a catalyst for a cathode electrode material or as an electrolyte material for PEFC.
A nano niobium oxide with high catalytic activity and a high performance niobium phosphate for use as a precursor to form an electrolyte to improve polymer fuel cell membrane performance is revealed by Tokyo Institute of Technology (Yokohama, Japan) Chemical System Synthesis Division Professor Takeo Yamaguchi, and his research team, Taichi Ito, Natsuhiko Kono, G.M. Anil Kumar, in U.S. Patent Application 20100009190. Nano niobium phosphate may also be used at the fuel cell cathode.
Niobium oxide is prepared by reacting a niobium compound, a chelating agent and a catalyst in a solvent in an inert gas atmosphere. Niobium oxide thus prepared is added phosphoric acid for phosphorylation in order to prepare niobium phosphate.
Niobium oxide is prepared by reacting a niobium compound, a chelating agent and a catalyst in a solvent in an inert gas atmosphere. Niobium oxide thus prepared is added phosphoric acid for phosphorylation in order to prepare niobium phosphate.
The process makes it is possible to manufacture niobium oxide with the nanoscale particle size. By niobium oxide with a nanoscale particle size is meant niobium oxide having a volume averaged particle size as measured by the dynamic light scattering method in a range from 0.9 nm to 12 nm.
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FIG. 4A is a TEM photo of niobium oxide manufactured by adding a chelating agent.
FIG. 7 is a TEM photo of nano niobium oxide manufactured without adding a chelating agent.
FIG. 4A is a TEM photo of niobium oxide manufactured by adding a chelating agent.
FIG. 7 is a TEM photo of nano niobium oxide manufactured without adding a chelating agent.
FIG. 1 is a flowchart for illustrating an example method for nanofabrication of nano niobium oxide
With the Tokyo Institute of Technology method for manufacturing nano niobium phosphate, niobium phosphate with high proton conductivity can be produced. Researchers confirmed it is possible to improve the performance of niobium phosphate as an electrolyte by reducing the particle size to the nanometer realm . The new niobium phosphate may be applied as an organic/inorganic hybrid material for PEMFC to improve performance.
