These photocatalysis sheets are perfect for shoe closets as their strong odor prevention properties can be renewed indefinitely just by exposing them in the sun. The sheets are on sale now at the Communication Center on the Hongo Campus (500 yen for a two-sheet set).
Interviewer: I鈥檝e heard that the history of research into photocatalysis at the University of Tokyo dates back 46 years.
Hashimoto: One day in the mid-1960s, my predecessor Professor Akira Fujishima was a graduate student at the University, working under the guidance of Professor Kenichi Honda. In an experiment he found that when titanium oxide and platinum electrodes were placed in water and exposed to light, the combination caused bubbles to appear in the water. The water in the experiment was decomposed into oxygen and hydrogen. It was a reaction that normally would not have been thought to be possible in electrochemistry. Professor Fujishima wrote up the results in his doctoral dissertation, but the examination board and the academic association refused to銆�accept his findings initially. However, in 1972 his research results were published in Nature and his results were given on a front-page in the Asahi Shimbun newspaper in 1974. Following this, his experiment was finally accepted by the academic association. Under normal circumstances water does not break down at a voltage of less than 1.23v, but this becomes possible when light energy is added. This reaction has become known as the 鈥淗onda-Fujishima effect,鈥� named after the two people involved in the discovery.
Interviewer: Why was the mass media so excited about this new, but somewhat academic discovery?
Hashimoto: It was the time of the first Oil Shock and was an era when everyone was searching for alternative energies. As hydrogen gathered from water can be used as a fuel, this discovery was catapulted into the limelight as one potential answer to energy issues.
Research into the utilization of powdered titanium dioxide began from around 1975. This method of using powdered titanium dioxide instead of electrodes is what is known as photocatalysis. However, photocatalysis of the powdered form of titanium dioxide did not produce good results. Although it was reported that results had been achieved, overall they were not very effective.
The second Oil Shock occurred in 1979. It was at that time that Dr. Tadayoshi Sakata and Dr. Tomoji Kawai of the Institute for Molecular Science, to which I was affiliated at the time, thought of adding (organic) alcohol to the water and creating a reaction that way. By adding the alcohol, they found that the powdered form of the titanium dioxide also released hydrogen in plentiful supply. It was subsequently found that the organic substance didn鈥檛 have to be alcohol. Leaves, urine, excrement鈥s long as it was an organic substance, anything would work. Even cockroaches were completely decomposed and produced hydrogen. This gave a tremendous boost to photocatalysis research, as everyone thought that the solution to the world鈥檚 energy problems had been found.
However, as research progressed, it was found that only small amounts of energy could be obtained through this process. The drawback of titanium dioxide photocatalysis is that it reacts exclusively under ultraviolet (UV) light, and only a very small fraction of such rays reach the Earth.
Interviewer: And this was going on around the time that you joined the laboratory of Professor Fujishima as a young researcher.
Hashimoto: In 1989 I was called in for what was initially going to be a two-year limited period, to act as a type of 鈥渟tand-in鈥� for another researcher. My child had just been born and the task in front of me was a real challenge. I was filled with a real sense of pessimism as I set about my work, realizing that I had to achieve results within the space of two years. The ceiling of my office in Engineering Building 5 was really low and my head was always scraping the asbestos ceiling. I think this had an adverse effect on my hair (laughs).
My office was on the first floor and Professor Fujishima鈥檚 was on the fourth. Every day I would go up and down to his office using the elevator, at the side of which was a restroom that was terribly dirty and smelly. It was while I was staring into the yellowed urinal that I suddenly had a eureka moment. If the photocatalysis reaction could decompose a cockroach, surely it could easily dec