Fabrication of High-Power Density Biofuel Cell Using Sericin Electrolyte and Anomalous Proton Conductivity

Biomaterials are expected to applicate to electrolytes for fuel cells that are next-generation energy in recent years. Particularly, it is hoped that the fuel cell using biomaterials has a higher power density. In the present work, we have attempted to fabricate a fuel cell based on biomaterials "sericin " which is a serine-rich protein obtained from the silkworm cocoon. As a result, we have succeeded to fabricate the fuel cell and found that its maximum power density shows approximately 3.3 mW/cm2. Further, we investigated key factors of the high power density of the fuel cell. From the analysis of the frequency dependence of AC proton conductivity, it is deduced that the formation of water bridges plays an important role in realizing proton conductivity in sericin. It was also found that the proton conductivity of sericin rapidly increases in an extremely narrow hydration number range from 1.77 to 1.82, and relaxation time for dielectric dispersion rapidly decreases. From these results, it is deduced that the high-proton conductivity in sericin is caused by the water bridge formed in this region as new proton transport pathways.