**2.2 Fabrication of the fuel cell based on chitin and operating condition**

**Figure 3** shows the shape of the fuel cell based on the chitin electrolyte. As show in **Figure 3**, the chitin electrolyte was inserted between Pt-C electrodes (anode and cathode). The current was collected from the current collector plates. The hydrogen and oxygen gases were introduced from the up and down sides of the fuel cell, respectively. In the fuel gas flow, the relative humidity, temperature and gas-flow ratio were controlled by the humidified gas-flow control system of Auto PEM (Toyo Corporation) at room temperature. The H2 gas flow rate and the air flow rate are 0.1 L/min and 0.25 L/min, respectively [8].

#### **2.3 Impedance and water contents measurements**

The water contents were measured from the relative humidity dependence of the weight of chitin using the electronic analytical balance (OHAUS Inc.) and the number of water molecules per a chitin molecule was calculated from the obtained water contents and molecular weights of water and mono-chitin [8]. The water content *n* was calculated using the following equation,

$$m = \frac{(w - d) / Mw}{d / Mw} \tag{1}$$

This time, *w* and *d* show each weight of wet and dry sample. *Mw* is molecular weight of water. *Mc* is molecular weight of mono-chitin or mono-chitosan.

The measurement of electrical conductivity was carried out using precision LCR meter (E4980A, Agilent Technologies Inc.). The relative humidity and temperature were con-trolled by the humidified gas-flow control system (Auto PEM). In the impedance measurement, the electrical conductivities perpendicular to the surface and parallel to the surface in chitin sheet were measured. In the case of chitin fiber specimens, impedance measurements were performed for specimens along the fiber direction and normal to the fiber direction, respectively [8–10].

*Chitin and Chitosan - Physicochemical Properties and Industrial Applications*
