期刊
ENVIRONMENTAL SCIENCE & TECHNOLOGY
卷 42, 期 9, 页码 3401-3406出版社
AMER CHEMICAL SOC
DOI: 10.1021/es8001822
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Hydrogen gas can be produced by electrohydrogenesis in microbial electrolysis cells (MECs) at greater yields than fermentation and at greater energy efficiencies than water electrolysis. It has been assumed that a membrane is needed in an MEC to avoid hydrogen losses due to bacterial consumption of the product gas. However, high cathodic hydrogen recoveries (78 +/- 1% to 96 +/- 1%) were achieved in an MEC despite the absence of a membrane between the electrodes (applied voltages of 0.3 < E-ap < 0.8 V; 7.5 mS/cm solution conductivity). Through the use of a membrane-less system, a graphite fiber brush anode, and close electrode spacing, hydrogen production rates reached a maximum of 3.12 +/- 0.02 m(3) H-2/m(3) reactor per day (292 +/- 1A/m(3)) at an applied voltage of E-ap = 0.8 V. This production rate is more than double that obtained in previous MEC studies. The energy efficiency relative to the electrical input decreased with applied voltage from 406 +/- 6% (E-ap = 0.3 V) to 194 +/- 2% (E-ap = 0.8 V). Overall energy efficiency relative to both Eap and energy of the substrate averaged 78 +/- 4%, with a maximum of 86 +/- 2% (1.02 +/- 0.05 m(3) H-2/m(3) day, E-ap = 0.4 V). At E-ap = 0.2 V, the hydrogen recovery substantially decreased, and methane concentrations increased from an average of 1.9 +/- 1.3% (E-ap = 0.3-0.8 V) to 28 0% of the gas, due to the long cycle time of the reactor. Increasing the solution conductivity to 20 mS/cm increased hydrogen production rates for E-ap = 0.3-0.6 V, but consistent reactor performance could not be obtained in the high conductivity solution at E-ap > 0.6 V. These results demonstrate that high hydrogen recovery and production rates are possible in a single chamber MEC without a membrane, potentially reducing the costs of these systems and allowing for new and simpler designs.
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