**3. Result and discussion**

### **3.1 Power density in chitin and chitosan fuel cells**

So far, we have revealed that power density in the fuel cell based on chitin or chitosan [8]. **Figure 4** shows *i-V* characteristics of the fuel based on the chitin. As shown in **Figure 4**, chitin electrolyte shows typical *i-V* curve and is also a polysaccharide material, but it has a high output, an open circuit voltage of 0.76 V and a power density of 1.35 mW/cm2 . The red dot in **Figure 4** shows the *i-V* characteristics when injecting unhumidified H2 gas, but it can be seen that the current obtained is very low. Chitosan did the same test, but its maximum power density was 0.032 mW/cm2 , which was lower than that of chitin. These results indicate that chitin and chitosan become the proton conductor with humidified condition. Moreover, it is expected that these differences are due to difference between chitin and chitosan, that is, the deacetylation degree of the chitin system.

#### **Figure 4.**

*i-V characteristics of fuel cell based on chitin electrolyte. Red and black dots show relation between open circuit voltage and current density. Black and red circle show power density.*

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**Figure 5.**

*FT-IR spectra of chitin sample [10].*

*Proton Conductivity in Chitin System*

of anomalous behavior [10].

water molecule how to behave in chitin system yet.

**3.3 Percolation conductivity in chitin**

*DOI: http://dx.doi.org/10.5772/intechopen.96799*

**3.2 Proton conductivity in chitin system**

Regarding the proton conductivity in chitin and chitosan, which have already revealed, these values in sheet specimens show approximately 10−4 ~ 10−1 S/m [1]. The proton conductivity of the chitin system sheet increases monotonically with increasing humidity, and the value of chitin is tens of times higher, especially when the relative humidity is changed from 60% to 100%. In the case of chitosan, its value changes approximately 10 times higher. Further, we focused on acetyl group in chitin, and have revealed that relationship between proton conductivity in chitin system and the deacetylation by using Fourier transform infrared spectrometer (FT-IR). **Figure 5** shows the FTIR spectrum of chitin used in the experiment [10]. It was found that the acetyl group plays important role for appearance of proton conductivity in chitin system because the degree of deacetylation gave conductivity

Furthermore, we have approached the proton conductivity in chitin system by using measurement of water contents and comparing chemical component. First, we have used sheet and fiber specimen of chitin, and measured the degree of swelling by microscopic observation after immersion experiment in water. As a result, it was confirmed that the sheet specimen was isotropically swelled in both the cross section and the in-plane, and the fiber specimen was anisotropically swelled by approximately 20% in both the fiber cross section and the fiber direction. From the above, it was clear that the chitin system introduced water molecules, so we made a comparison based on the water content and chemical component. The results obtained by these researches indicated that injection of water molecule and existence of acetyl group for promotion it, that is necessary to appearance of the proton conductivity in chitin system. However, it has not been completely understood that

In order to clarify the role of water molecules in chitin, we obtained the volume fraction of water molecules with respect to chitin molecules from the results of the relative humidity dependence of the hydration number, and investigated the relationship with proton conductivity. Yamada *et al*. measure the resistance value that changes by gradually increasing the volume fraction of the conductor material in the non-conductor material [12]. As a result, Yamada *et al*. report that the resistance *Chitin and Chitosan - Physicochemical Properties and Industrial Applications*

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**Figure 4.**

**3. Result and discussion**

*Fuel cell based on the chitin.*

**Figure 3.**

a power density of 1.35 mW/cm2

was 0.032 mW/cm2

**3.1 Power density in chitin and chitosan fuel cells**

So far, we have revealed that power density in the fuel cell based on chitin or chitosan [8]. **Figure 4** shows *i-V* characteristics of the fuel based on the chitin. As shown in **Figure 4**, chitin electrolyte shows typical *i-V* curve and is also a polysaccharide material, but it has a high output, an open circuit voltage of 0.76 V and

teristics when injecting unhumidified H2 gas, but it can be seen that the current obtained is very low. Chitosan did the same test, but its maximum power density

that chitin and chitosan become the proton conductor with humidified condition. Moreover, it is expected that these differences are due to difference between chitin

*i-V characteristics of fuel cell based on chitin electrolyte. Red and black dots show relation between open circuit* 

*voltage and current density. Black and red circle show power density.*

and chitosan, that is, the deacetylation degree of the chitin system.

. The red dot in **Figure 4** shows the *i-V* charac-

, which was lower than that of chitin. These results indicate
