Method for preparing air cathode of microbial fuel cell by using petroleum cokes

[0031] Example 1:

[0032] The preparation method of the petroleum coke activator air cathode in the present invention includes the following steps:

[0033] Activation of petroleum coke

[0034] Put the petroleum coke solid into a ball mill and grind to a particle size of less than 200 microns as the raw material for the next activation. Mix a certain amount of petroleum coke powder and KOH according to a weight ratio of 4:1, and place in a mortar to continue grinding, so that the two can be evenly mixed. The mixed powder is placed in a porcelain boat, placed in a tube furnace, and activated under the protection of nitrogen.

[0035] The activation process includes preliminary activation and final activation. The initial activation is to increase the temperature of the tube furnace to 300 degrees Celsius at a heating rate of 3°C/min and keep it for one hour. The final activation is based on the preliminary activation, raising the temperature of the tube furnace to 800°C at a heating rate of 5°C/min, and keeping it for 1 hour.

[0036] After the two-step activation process is over, the petroleum coke activation product is placed in a nitrogen environment to cool, and then taken out. Rinse with deionized water until the pH is close to neutral, then place it in a drying oven at 80°C for more than two days. The dried activated product is placed in a mortar and ground into powder for use in making an air cathode catalytic activation layer.

[0037] Fabrication of air diffusion layer

[0038] Immerse the conductive carbon black in a certain amount of absolute ethanol and stir under ultrasonic conditions. After stirring evenly, add PTFE according to the ratio of conductive carbon black: PTFE weight ratio 3:7, and continue to stir under ultrasonic conditions , Until the elastic micelle appears. Roll this micelle into a 0.5mm thin layer, and then roll it to the surface of the stainless steel mesh, and continue rolling until the final thickness reaches 0.6mm. The air diffusion layer is calcined in a muffle furnace for 20 minutes.

[0039] Production of catalytic activation layer

[0040] The petroleum coke activation product prepared in the first step is immersed in a certain amount of absolute ethanol, and stirred under ultrasonic conditions to completely mix the two. On this basis, add a certain proportion of polytetrafluoroethylene, continue to stir under ultrasonic conditions, until the formation of elastic micelles. The micelle is rolled into a thin layer with a thickness of 0.5mm, and the thin layer is rolled onto the other side of the second step stainless steel mesh of the stainless steel mesh, and the rolling is continued until the final thickness reaches 1mm.

[0041] Drying of air cathode

[0042] Place the prepared air cathode in a drying box at 80° C. and dry for 12 hours for later use.

[0043] The scanning electron micrographs of the petroleum coke activated material and ordinary activated carbon prepared in this example are as follows figure 1 a and figure 1 As shown in b, the surface of activated petroleum coke is more irregular than ordinary activated carbon, and there are small spherical substances on the surface. These irregular structures increase the specific surface area of ​​the electrode, that is, the reduction reaction of oxygen obtains more reaction sites . The linear scanning voltammogram of petroleum coke and common activated carbon air cathode figure 2 As shown, under the same electrode potential, the current density of the petroleum coke activator air cathode is higher than that of ordinary activated carbon. Both the petroleum coke activator electrode and the ordinary activated carbon electrode were installed on a single-chamber microbial fuel cell for testing. The cell polarization curve and power density curve are as follows image 3 As shown, the maximum power density of petroleum coke activator air cathode battery is significantly higher than that of ordinary activated carbon air cathode battery. The electrode potential of the above-mentioned different air cathode batteries varies with current density as Figure 4 As shown, the anode potential of the two batteries is basically the same as the current density, while the cathode potential of the petroleum coke air cathode is significantly higher than that of the activated carbon electrode, showing better cathode performance.