Research On Preparation Of Nitrogen-doped Activated Carbon Catalyst For Oxygen Reduction And Efficiency Assessment

Microbial fuel cell (MFC) is a new environmental technology for wastewater treatment with simultaneous energy recovery in 21st century. In MFC, chemical energy from organic pollutant can be directly converted into electrical energy by anodic exoelectrogenic bacteria, the one uses the oxygen in the air as the cathodic catalyst for oxygen reduction reaction (ORR) called Air-cathode Microbial Fuel Cell (ACMFC). However, the expensive platinum (Pt), which serves as the indispensable ORR catalyst in cathodes, dramatically increases the cost of ACMFC.Therefore research on lower cost buthigheractivity of catalystis becoming a key factor to reduce the total cost of ACMFC.Activated carbon powder (denoted as AC) and super capacitor activated carbon (SC) were adopted and treated by nitric acid, carbamide and ammonium carbonate. Higher activity was always determined for activated carbon powder AC than super capacitor activated carbon SC and with any of treatment methods among which carbon powder treated by nitric acid was highest, followed by ammonium carbonate and carbamide. The same trend was also observed for electron transfer number by Rotating Disk Electrode (RDE). X-ray photoelectronic spectroscopy (XPS) analysis indicated nitrogen oxide and pyridinic-type nitrogen were the main functional groups to affect catalytic activity. Carbon powder treat by urea has a wider pH (pH,5～11) range.The electrochemical impedance spectrum show the resistance of nitrogen-doped cathode are reduced, the untreated AC cathode resistance is lower than untreated cathode SC, the resistance of carbon powder treated by carbamide was lowerest, followed by ammonium carbonate and nitric acid.In terms of electricity output of ACMFC, for the sodium acetate water, the higher maximum power density (Pmax) of activated carbon powder AC was 1470 mW/m2 compared with 1390mW/m for super capacitor activated carbon SC. The highest Pmax was obtained with carbon powders treated by carbamide which increased by 12.2% to 1560mW/m2 for super capacitor activated carbon SC, and 22.3% to 1798mW/m2 for activated carbon powder AC. also,22.3% increment was obtained for activated carbon powder AC than super capacitor activated carbon SC when carbamide was adopted.The decreased catalytic activity of carbon powder treated by nitric acid was also observed and likely related to the nitrogen dissolution. Results showed that the rule of energy production with municipal wastewater is consistent with that of sodium acetate water, Which carbamide-doped activated carbon has both high coulombic efficiencies (the highest utilization of electronic) and actual wastewater COD removal rates.Based on specific cost for electricity production, the carbamide-doped activated carbon powder AC was 83.1% that of original carbon powder AC, and only 15.4% that of original carbon powder SC. Therefore, not only the cost of catalyst can be reduced, but also larger electricity output can be achieved when carbamide-doped activated carbon powder AC was used as catalyst. The carbamide-doped cathode holds broader prospects in municipal wastewater for building large scale microbial fuel cell. After we removed the biofilm from the cathode, the performance could restore for the reactors operated for 6 days. But that operated about 15 or 30 days didn’t improve, it may be because over time the biofilm could enter catalyst layer and block the micropore.