World’s First Use of Bio-Process for Forming Platinoid Element Nanoparticle Catalyst

A bio-process has successfully formed platinoid element nanoparticle catalyst.
Specifically, iron-reducing bacteria (IRB) were used for forming the catalyst.
This process is different from the conventional engineering process.
This is the world’s first success.
The bio-process is economic and environment friendly.

Developed by:
Dr. Yoshinori Suzuki and Toshihiko Ohnuki, chief researcher (Advanced Science Research Center, Japan Atomic Energy Agency)
Professor Yohichi Enokida and joint research team (EcoTopia Science Institute, Nagoya University)

As is known, the platinoid element has an excellent catalytic ability.
The platinoid element has been used for fuel cells, for removing causative agents of photochemical smog, acid rain, etc., isotope exchange, for isotope exchange.
The nanoparticle has a large ratio of the surface area to the volume.
Many processes to form the platinoid element nanoparticle catalyst have been developed and are currently used. Those processes suffer from problems, however.

The physically crushing method has the following problems: When large particles are crushed into nanoparticles, impurity substances are mixed into the nanoparticles (poor impurity), and nanoparticles tend to agglutinate.
The chemical precipitation method needs a large-scale system for making the nanoparticle grow from a seed as chemical reaction proceeds.
Much efforts have been made to seek the best ways to form the nanoparticle catalyst all over the world. It is note that in such circumstances, the bio-process to form the nanoparticle catalyst has been created.

The researchers focused attention on the fact that specific microorganisms couple to the transuranic element, for example.
Iron-reducing bacteria were added to a platinic acid solution and a palladium acid solution. It was observed that platinoid particles of nano-scale were formed on the cell of the iron-reduction bacterium (see Fig. 1).
“Microorganism cells - platinoid particles” were placed on diatomaceous earth for the isotope exchange hydrogen (H2) with deuterium (D2) (H2 + D2 → 2HD).
The efficiency of the isotope exchange was about 6 times of that when only the platinum particles are used. Excellent catalytic ability was exhibited.

The researchers said:
1) The iron-reducing bacteria have other functions, for example, function to mineralize uranium.
2) The possibility is present that other microorganisms, for example, yeast, have excellent functions.
3) We hope to find other functions of the microorganism, to elucidate their mechanisms and to propose additional bio-processes.
4) We hope to develop new catalysts that are operable in intensive radiation conditions.
[Excerpted from Press Release by Japan Atomic Energy Agency]