Performance and biotoxicity evaluation of sulfur-doped graphene as a cathode for MFC
Sulfur-doped reduced graphene oxide(S-rGO)materials were prepared by hydrothermal method.The characterization revealed that doping of S atoms led to the formation of structural defects in the rGO,which increased the active site of the material.Electrochemical tests revealed that S-rGO exhibited better oxygen reduction reaction(ORR)performance than rGO.The limited current density of S-rGO was 4.08mA/cm2,which was 17.3%higher than that of rGO(3.48mA/cm2).This indicates that the S atom doping can effectively improve the ORR activity of rGO.S-rGO was mixed with activated carbon(AC)and carbon black(CB)at a mass ratio of 0.1∶0.25∶1 to prepare the cathode catalyst for microbial fuel cells.The results showed that the S-rGO-catalyzed microbial fuel cell reactor could operate for 27h per cycle and generate an output voltage of 0.33V,while the rGO-catalyzed reactor could run for 24h per cycle with an output voltage of 0.30V.The reactor catalyzed by CB could last for 23h per cycle and had an output voltage of 0.26V.Benzalammonium chloride(BAC)was used as a biotoxic substance to test the toxicity sensing performance of the S-rGO-modified microbial fuel cells.The linear fitting results of voltage and BAC concentration revealed that S-rGO had higher sensitivity and stability for toxicity detection(correlation coefficient was 0.996),whereas the correlation coefficient of the traditional Pt/C cathode catalyst was 0.932.All the above results indicates that S-rGO has great potential for application in the field of toxicity detection.
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