Tokyo Tech News

Soft X-rays: New Visualization Tool for Light Weight Elements in Energy Devices


Published: January 31, 2011

The details of research

Substances composed of light atomic mass elements are extensively used for the manufacture of energy devices and play significant roles as reactants, products, catalysts, and solvents.

However, such substances are difficult to visualize using conventional X-ray radiography (>100keV) because of the poor absorption of such high energy X-rays by such substances.

Now, Shuichiro Hirai and colleagues at Tokyo Institute of Technology demonstrate that soft X-rays—with energies less than 2keV—enable the enhancement of X-ray absorption by the visualization of liquid water emerging from an operating proton exchange membrane fuel cell (PEMFC).

The researchers tuned the new soft X-ray radiography system—which has a spatial resolution of <1µm and temporal discrimination of <1sec—for the visualization of liquid water in PEMFC by optimization of the emitter and detector optics.

The tremendous potential of this system was seen by the observation that liquid water was generated preferentially underneath the ribs in the cathode, thereby preventing the supply of oxygen from the channel to the electrodes, which results in the degredation of cell performance (Fig.1).

Soft X-rays show potential for in situ visualization of not only energy devices, such as fuel cells, but also in bio-systems.


  • Authors: Takashi Sasabe, Shohji Tsushima, and Shuichiro Hirai
  • Title of original paper: In-situ visualization of liquid water in an operating PEMFC by soft X-ray radiography
  • Journal, volume, pages and year: International Journal of Hydrogen Energy 35, 11119 (2010).
  • Digital Object identifier (DOI): 10.1016/j.ijhydene.2010.06.050.
  • Affiliations: Department of Mechanical and Control Engineering, Graduate School of Science and Engineering, Tokyo Institute of Technology
  • Department website:

Soft X-ray visualization of liquid water in an operating PEMFC.

Soft X-ray visualization of liquid water in an operating PEMFC.

Shuichiro Hirai
Graduate School of Science and Engineering Mechanical and Control Engineering