Energy transport and storage system should be considered with new energy source installation such as solar and wind power. There are some methods for it, and organic hydride methods are highly paid attention. In these methods, toluene-methylcyclohexane (MCH) conversion system is a good candidate as an energy transport and storage system with some reasons such as easy handling, affinity with Japanese current infrastructure, and so on. In the toluene-MCH conversion system, direct-toluene hydrogenation is especially paid attention since the system can be easier and exothermic heat loss reaction is less than other methods, so total efficiency of direct method gets higher than other methods.

However, there are some problems on it, and the most serious problem is optimizing water management in cathode [1,2]. In cathode, toluene and MCH are flowing, and water appears in cathode porous transport layer (PTL) by being transported from anode then the water interrupts fuel supplies and the conversion rate from toluene to MCH gets lower. Therefore, water management should be optimized for higher performance of the system. However, there is no research which is focusing on water movement in this system as far as we know.

Therefore, in this study, the original cell was investigated which had a visualization window on the cathode surface and allowed us to visualize the water movement during operating the system, and water movement was investigated. Fig. 1 shows the cell configuration and the actual picture from visualization window. As shown in Fig.1(a), the original cell was developed. In the left side, there is a visualization window with sapphire glass and the surface of the cathode PTL can be shot by hi-speed camera and so on. Fig.1(b) shows the example of visualization results. The cell was set with the gravity direction lower side and flow direction upper. The image shows us cathode PTL and toluene-MCH flow with water droplet and hydrogen bubble. As it can be seen in Fig.1(b), there are some droplets with several sizes. The 0.5 – 1.5 mm diameter droplets can be recognized as water droplet by seeing the movement with movie. By using this system, the effects of different anode supplies were discussed on water and hydrogen generation.

Reference

[1] K. Nagasawa et al., Electrochemistry, 339-344, 86 (2018)

[2] K. Nagasawa et al., Electrocatalysis, 164-169, 8 (2017)