| Summary: | 碩士 === 國立勤益科技大學 === 化工與材料工程系 === 102 === In this thesis, the ordered nanofibric polyaniline (PANi) is electropolymerized on Au/Al2O3 electrode prepared by the microfabricated technique. Nafion®/Pt/nano-structured PANi/Au/Al2O3 used as the sensing electrode of the amperometric hydrogen sensor is prepared by electrodepositing Pt on the nano-structured PANi and then casting a suitable amount of Nafion® solution on the surface of electrode.
The diameter of PANi nanofiber and the particle size of electrodeposited Pt analyzed by SEM are found to be 40 – 50 and 5 – 20 nm, respectively. Decreasing the charge for electrodepositing Pt from 0.15 to 0.009375 C the electroactive area and roughness factor of Pt on Pt/nano-structured PANi/Au/Al2O3 electrode decreases from 1.406 × 10-3 m2 and 56.24 to 2.90 × 10-4 m2 and 11.60, respectively. However, decreasing the Pt deposition charge from 0.15 to 0.009375 C the specific Pt electroactive area increases from 47.06 to 155.08 m2 g-1 due to the better distribution of Pt particles onto the nano-structured PANi.
Using Nafion®/Pt(0.15 C)/nano-structured PANi/Au/Al2O3 as sensing electrode, the on-set potential for the anodic oxidation of H2 is found to be -0.4 V (vs. Au). For potential in the range of -0.4 – -0.3 V(vs. Au), the anodic oxidation of H2 is located in kinetic control region and the current increases with potential. The anodic oxidation of H2 is controlled by the mass transfer and the limiting current is obtained to be 14.528 μA cm-2 for the potential greater than -0.3 V (vs. Au).
The sensitivity of amperometric H2 gas sensor based on Nafion®/Pt/nano-structured PANi/Au/Al2O3 found to be 3.654 × 10-4 μA ppm-1 is 273.5 times of that based on Nafion®/Au/Al2O3 with sensitivity of 1.336 × 10-6 μA ppm-1. Using Nafion®/Pt/nano-structured PANi/Au/Al2O3 as sensing electrode, the specific sensitivity of the amperometric H2 gas sensor increases from 12.21 to 138.80 μA ppm-1 g-1 by decreasing the Pt electrodepositing charge from 0.15 to 0.009375 C. The sensitivity of amperometric H2 gas sensor based on Nafion®/Pt (0.009375 C)/nano-structured PANi/Au/Al2O3 changes slightly by increasing the gas flow rate from 200 to 500 ml min-1 due to the insignificant mass transfer resistance witin the gas diffusion layer for gas flow rate greater than 200 ml min-1. On the other hand, decreasing the amount of Nafion® solution from 5 to 3 μl for preparing sensing electrode the significant increase in the sensitivity of amperometric H2 gas sensor is due to the decrease in the mass transfer resistance within the Nafion® film. The sensitivity of amperometric H2 gas sensor decreases from 4.19 × 10-4 to 1.32 × 10-4 μA ppm-1 with decreasing the relative humidity from 100 to 23 %.
|
|---|
