Bio-CNF and N-CNT Composites for Rechargeable Zinc-Air Battery Cathode Modification

• Main Authors: Yu-chien Kuo, 郭聿倩
• Other Authors: 吳石乙
• Format: Others
• Language: zh-TW
• Published: 2016
• Online Access: http://ndltd.ncl.edu.tw/handle/50261575848961994055

碩士 === 逢甲大學 === 化學工程學系 === 104 === The main aim of this research is to develop rechargeable Zinc-air battery using composite carbon materials as the air cathode. In the first part of the research, biological carbon nano-fiber (Bio-CNF) was developed by carbonizing bacterial cellulose (BC) as support materials for cathode. The BC was produced through fermentation using factory’s waste byproducts. The effect of temperature on carbonization was also observed. Through BET analysis, it was observed that carbonizing BC at 1100°C (Bio-CNF1100) led to highest surface area and significantly thinner than other carbon materials. Hence, the Bio-CNF1100 results into higher gas permeability and smaller reduction current. Nitrogen-doped carbon nanotube (N-CNT) was added to Bio-CNF in order to decrease three phase phenomenon caused by high gas permeability. Bifunctional air electrode was synthesized from CoO, Co3O4 and Ni-Fe on different carbon supports. It was found that electrode with composition of CoO/(Bio-CNF1100:N-CNT;1:1) acts as the oxygen reduction reaction (ORR) site and has higher activity than Pt. The cycling of long time, it showed 0.75 V of overpotential at first cycle and after 55 hours was 1.03 V at 5 mA/cm2. The cycling of short time, it showed 1.13 V of overpotential at first cycle and 1.74 V after 100 cycles at 20 mA/cm2. In the second part, the research selected electrode composition with preferred performance electrical catalysts was mixed in different proportions with Ni-Fe LDH/N-CNT. Although Ni-Fe LDH/N-CNT don’t lead to ORR, it has better oxygen evolution reaction (OER). The cycling of long time, CoO/(Bio-CNF1100:N-CNT;1:1) when mixed with Ni-Fe LDH/N-CNT in the three ratios (1 : 1, 1 : 2, 2 : 1) has lower overpotential (about 1.5 V) than other tested catalysts composition. In conclusion, utilizing CoO/(Bio-CNF1100:N-CNT;1:1)/Ni-Fe LDH/N-CNT ratio is 1 : 2 led to highest power density of 17.7 mW/cm2