The National Institutes for Quantum and Radiological Science and Technology (Quantitative Research Institute), Shibaura Institute of Technology, and Japan Atomic Energy Agency have succeeded in significantly saving energy in the main reaction of the thermochemical hydrogen production process (a reduction of nearly 7% compared to the conventional method).Based on this result, we have a prospect of achieving a hydrogen production efficiency of 40%, which is an indicator of technological feasibility.
As a large-scale and stable production method of hydrogen, the IS process, which thermally decomposes water with a compound of iodine (I) and sulfur (S), is attracting attention.In order to improve hydrogen production efficiency, it is necessary to reduce the overvoltage of the Bunsen reaction, which is the main reaction of the IS process, from the conventional 0.65V to 0.2V.Since about 7% of the reaction overvoltage is overvoltage due to the resistance of the cation exchange membrane, it is important to reduce the resistance of the membrane.
Therefore, Quantum Research Institute has developed a new low-resistance cation exchange membrane using "quantum beam graft / cross-linking technology".Shibaura Institute of Technology has developed a porous gold anode to reduce the overvoltage caused by the anode reaction (sulfuric acid production reaction).The Japan Atomic Energy Agency has found that the optimum temperature for the Bunsen reaction is 50 ° C.
The developed cation exchange membrane and gold anode were incorporated into a membrane Bunsen reactor and tested at 50 ° C.Compared with the conventional test, the overvoltage of the membrane resistance could be reduced by about 8% and the overvoltage of the anodic reaction could be reduced by about 4%.As a result, we succeeded in reducing the overall reaction overvoltage to the target value of 0.2V.This result shows for the first time in the world that it is expected to achieve a hydrogen production efficiency of 650% even at a relatively low temperature of 40 ° C, which is the heat of the sun.
In the future, aiming for practical use, we plan to integrate each elemental technology established in the project and carry out a small-scale hydrogen production test.If the technology for the solar-heated IS process can be established, it will be possible to produce a large amount of hydrogen and supply it to fuel cell vehicles and household fuel cells, which is expected to make a great contribution to the construction of a "hydrogen society."
