Optimizing biochar and conductive carbon black composites as cathode catalysts for microbial fuel cells to improve isopropanol removal and power generation

A cathodic metal-based catalyst in a microbial fuel cell (MFCs) is costly so alternative carbon-based materials, such as biochar, are favored. Biochar that is obtained from agricultural waste (peanut husks) was combined with high-conductivity conductive carbon black (CCB) to form a cathodic composite catalyst (biochar/CCB). The optimal ratio of biochar/CCB (70% over 30%) and its volume (4.45 cm3) were obtained by response surface methodology (RSM). A cathode catalyst with low resistance (55.1 omega) and a high reduction peak current (7.26 mu A) was developed with an overall regression model explanatory power (R2) >0.95. Following the optimal biochar/ CCB modification, the removal efficiency, voltage output, power density and Coulombic efficiency of the MFC were 6.91-21.6%, 1.82, 2.47 and 2.56 times higher, respectively, than those of a carbon MFC without a catalyst. The microbial community of the anode indicates that the cathode modified by biochar/CCB can promote the growth of electrogenic and degrading bacteria to achieve improved power production and pollutant removal efficiency. This result demonstrates that the optimized biochar/CCB in this study has great potential for sub-sequent use in pollutant treatment and power generation systems.