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Low power density, a main drawback in a mediator-type microbial fuel cell (MFC), has been greatly increased by immobilizing bacteria using carbon nanoparticles. Proteus vulgaris-containing carbon paste was prepared by mixing bacteria suspension with carbon nanoparticles using Teflon emulsion. Thus, prepared carbon paste was spread on the carbon cloth and used as an anode. Higher power density was obtained than when bacteria were suspended in solution. The maximum power density of 705mWnormalm−2 was achieved. Various electrode preparation conditions as well as operating conditions have been examined. Impedance measurements suggested that performance improvement came from the decrease in ohmic, charge-transfer, and diffusion resistances. This work demonstrates the importance of bacteria immobilization in enhancing the power density of a MFC.

A microbial electrolysis cell, though considered as a promising, environmentally friendly technology for hydrogen production, suffers from concomitant production of methane. The high hydrogen/methane ratio at the initial operation stage decreases with time. Here we report for the first time the photoassisted microbial electrolysis cell (MEC) for persistent hydrogen production using polyaniline nanofibers as a cathode. Under 0.8 V external bias and laboratory fluorescent light illumination in a single-chamber MEC, continuous hydrogen production from acetate at a rate of 1.78 mH2 m d with 79.2 % overall hydrogen recovery was achieved with negligible methane formation for six months. Energy efficiencies based on input electricity as well as input electricity plus substrate were 182 and 66.2 %, respectively. This was attributed to the p-type-semiconductor characteristics of polyaniline nanofibers in which photoexcited electrons are used to reduce protons at the surface and holes are reduced with electrons originating from acetate oxidation at the anode. This method can be extended to microbial wastewater treatment for hydrogen production.

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Domestic and industrial wastewaters are subject to the biological treatment process before discharged to environment. In that process, organic substances contained in the wastewater are degraded by microorganisms. Microbial electrolysis cells (MECs) are suitable technology for wastewater treatment, simultaneously producing hydrogen. In most case, however, a significant amount of methane instead of hydrogen is produced when the wastewater is used for MECs. Here we show that hydrogen is the main product when Makgeolli wastewater (MW) is used as a substrate in a single‐chamber MEC which was operated using acetate and MW. Although current generation profiles vary according to the substrate type and the applied voltage, hydrogen portions were maintained over 90% at −0.6 V and −0.8 V with production rates of 0.95 and 1.55 m3H2/m3/d, respectively. This result shows a possibility of implementing MECs in the real wastewater treatment and hydrogen production.