A hybrid microbial fuel cell stack based on single and double chamber microbial fuel cells for self-sustaining pH control

•We proposed a hybrid microbial fuel cell stack for self-sustaining pH control.•The hybrid stack was based on single and double chamber MFCs.•The hybrid stack demonstrated a high operational stability.•An improved stack performance was obtained in the hybrid stack.•The hybrid stack showed efficient conversion of acetate to electricity.

Proton accumulation in the anode chamber is the major problem that affects the operational stability and electricity generation performance of double chamber microbial fuel cells (MFCs). In this study, a hybrid microbial fuel cell stack (DS–DS stack) based on single (SCMFCs) and double chamber MFCs (DCMFCs) is proposed for self-sustaining pH control in the MFC stack. It is found that the aerobic microbial oxidation of acetate by the biofilm that is attached to the air cathode of SCMFCs is responsible for the self-sustaining removal of accumulated H+ in the effluent of DCMFCs. Compared with the stack that solely consists of SCMFCs (SS–SS stack) or DCMFCs (DD–DD stack), the hybrid stack exhibits the highest electricity output performance and the most effective conversion of acetate into electricity at high power levels. Furthermore, the hybrid stack demonstrates the operation time of 15.7 ± 1.1 h when the operating voltage is above 0.8 V. This value is much higher than that of the DD–DD (8.5 ± 2.4 h) and SS–SS (8.1 ± 1.4 h) stacks, which suggests that the hybrid stack had a good operational stability.

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