Acidic and alkaline pretreatments of activated carbon and their effects on the performance of air-cathodes in microbial fuel cells

Activated carbon (AC) is a high performing and cost effective catalyst for oxygen reduction reactions (ORRs) of air-cathodes in microbial fuel cells (MFCs). Acidic (HNO3) and alkaline (KOH) pretreatments on AC at low temperature (85 °C) are conducted to enhance the performance of MFCs. The alkaline pretreatment increased the power density by 16% from 804 ± 70 to 957 ± 31 mW m−2, possibly due to the decrease of ohmic resistance (from 20.58 to 19.20 Ω) and the increase of ORR activities provided by the adsorbed hydroxide ion and extra micropore area/volume after alkaline pretreatment. However, acidic pretreatment decreased the power output to 537 ± 36 mW m−2, which can be mainly attributed to the corrosion by adsorbed proton at the interface of AC powder and stainless steel mesh and the decreased pore area.