Developing a self-powered microfluidic microbial electrolysis cell (MEC) for converting oxalate into hydrogen

The present study investigated the capability of coupled microfluidic microbial electrolysis cell-microbial fuel cell (MEC-MFC) to remove oxalate as a toxic end-metabolite and produce hydrogen as an effective antioxidant without any external power. The modification of the system to enhance the hydrogen generation and reduce the number of microfluidic MFCs supporting the external power supply of the microfluidic MEC was implemented by using zinc anode and inoculation of Shewanella oneidensis MR-1 at a simple straight microchannel. The selection of the mentioned elements resulted from the assessment of spiral and straight geometries, nanoparticle growth, and injection rates of the substrate. The open-circuit potential of one microfluidic MFC was obtained at about 1.3 V, which could quickly run MECs. The maximum hydrogen production rate was 1.12 mol H-2 mol Substrate(-1) day(-1), which was 12 times more than the results obtained by the coupled microfluidic MFC-MEC fed by glucose and using a nickel electrode. The performance of the coupled system was characterized by the polarization curves, the evolution of hydrogen production, and the morphology of the formed biofilm on the anode surface.