H2 production in membraneless bioelectrochemical cells with optimized architecture: The effect of cathode surface area and electrode distance

•MEC performance showed an indirect relationship with cathode surface area.•Larger electrode spacing (4 cm instead of 1 cm) resulted in better H2 production.•Electron transfer mechanism was investigated by cyclic voltammetry.

In this work we report on the hydrogen production capacity of single-chamber microbial electrohydrogenesis cell (MEC) with optimized design characteristics, in particular cathode surface area and anode-cathode spacing using acetate as substrate. The results showed that the maximal H2 production rates and best energetic performances could be obtained using the smallest, 71 cm2 stainless steel cathode and 4 cm electrode distances, employing a 60 cm2 bioanode. Cyclic voltammetric analysis was employed to investigate the dominant electron transfer mechanism of the architecturally optimized system.