A Solar-Powered Microbial Electrolysis Cell With a Platinum Catalyst-Free Cathode To Produce Hydrogen
Department of Environmental Science and Engineering, Gwangju Institute of Science and Technology, 1 Oryong-dong, Buk-gu, Gwangju 500-712, South Korea.Environmental Science and Technology (Impact Factor: 5.33). 12/2009; 43(24):9525-30. DOI: 10.1021/es9022317
This paper reports successful hydrogen evolution using a dye-sensitized solar cell (DSSC)-powered microbial electrolysis cell (MEC) without a Pt catalyst on the cathode, indicating a solution for the inherent drawbacks of conventional MECs, such as the need for an external bias and catalyst. DSSCs fabricated by assembling a ruthenium dye-loaded TiO(2) film and platinized FTO glass with an I(-)/I(3)(-) redox couple were demonstrated as an alternative bias (V(oc) = 0.65 V). Pt-loaded (0.3 mg Pt/cm(2)) electrodes with a Pt/C nanopowder showed relatively faster hydrogen production than the Pt-free electrodes, particularly at lower voltages. However, once the applied photovoltage exceeded a certain level (0.7 V), platinum did not have any additional effect on hydrogen evolution in the solar-powered MECs: hydrogen conversion efficiency was almost comparable for either the plain (71.3-77.0%) or Pt-loaded carbon felt (79.3-82.0%) at >0.7 V. In particular, the carbon nanopowder-coated electrode without Pt showed significantly enhanced performance compared to the plain electrode, which indicates efficient electrohydrogenesis, even without Pt by enhancing the surface area. As the applied photovoltage was increased, anodic methanogenesis decreased gradually, resulting in increasing hydrogen yield.
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- "Recently, a significant number of researchers have reported that the performance of MEC is greatly influenced by several factors, such as initial pH, temperature  , electrolyte solution [6e9], substrates and anode surface area [10e12], microbial anode potential (MAP) , electrode materials and electrode spacing  , cell internal and external resistance [16e18], and activated sludge concentration . Of these factors, cathode material with the high performance is the most important factor in the performance of MECs where H 2 as well as other value-added chemical compounds are produced. "
ABSTRACT: Microbial electrolysis cells (MECs) are generally regarded as a promising future technology for manufacturing green hydrogen from organic material present in wastewaters and other renewable energy sources. However, the development of inexpensive and high-efficient cathode catalyst is the most critical challenge for MECs to become a commercialized H2 production technology. In this study, a non-noble metal electroformed Ni mesh cathode alternatives to typical cathode material (Pt/CC) was intensively examined in a single-chamber membrane-free MEC. To the best of our knowledge, the use of electroformed Ni mesh as the MEC cathode catalyst has not been reported so far. The MEC was operated in fed-batch mode and the performance of the Ni mesh cathode was compared with that of Pt/CC cathode in terms of columbic efficiencies (75 ± 4% vs. 72.7 ± 1%), overall hydrogen recovery (89.3 ± 4% vs. 90.9 ± 3%), overall energy efficiency (62.9 ± 5% vs. 69.1 ± 2%), the maximum volumetric hydrogen production rate (4.18 ± 1 m3 H2/m3 d vs. 4.25 ± 1 m3 H2/m3 d), volumetric current density (312 ± 9 A/m3 vs. 314 ± 5 A/m3). The obtained results in this study highlight the great potential of using the electroformed Ni mesh catalysts as a viable cathode material for hydrogen production in MECs.
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- "In this system, the MFC acted as an external energy source to produce hydrogen at the MEC cathode. A solar-powered MEC with a Pt catalyst-free cathode was reported for the production of hydrogen (Chae et al., 2009). Because both the MFC and solar cell use renewable energy, the application of them as the external energy sources for MEC operation can extend this technology in practical fields. "
ABSTRACT: Microorganisms naturally form biofilms on solid surfaces for their mutual benefits including protection from environmental stresses caused by contaminants, nutritional depletion or imbalances. The biofilms are normally dangerous to human health due to their inherited robustness. On the other hand, a recent study suggested that electrochemically active biofilms (EABs) generated by electrically active microorganisms have properties that can be used to catalyze or control the electrochemical reactions in a range of fields, such as bioenergy production, bioremediation, chemical/biological synthesis, bio-corrosion mitigation and biosensor development. EABs have attracted considerable attraction in bioelectrochemical systems (BESs), such as microbial fuel cells and microbial electrolysis cells, where they act as living bioanode or biocathode catalysts. Recently, it was reported that EABs can be used to synthesize metal nanoparticles and metal nanocomposites. The EAB-mediated synthesis of metal and metal-semiconductor nanocomposites is expected to provide a new avenue for the greener synthesis of nanomaterials with high efficiency and speed than other synthetic methods. This review covers the general introduction of EABs, as well as the applications of EABs in BESs, and the production of bio-hydrogen, high value chemicals and bio-inspired nanomaterials.
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- "MEC ARB Acetate – 9.42 Chae et al. (2009) the existing systems. Particularly, the granule-based reactors, thermophilic processes, and integrated systems hold great promise for practical application, but many challenges are yet to be addressed. "
ABSTRACT: This chapter discusses high-rate hydrogen-producing bioreactors based on their HPR (hydrogen production rate), HY (hydrogen yield), biomass retention capability, and process stability. Development of bioreactors presents one important aspect of the fast progressing biohydrogen production technologies. It is widely accepted that the reactor configuration and operating mode can pose significant influences on the system biohydrogen production performance by directly affecting the hydrodynamics and bacteria properties. Both volumetric HPR and HY have been considered as important indexes to evaluate the performance of a biohydrogen production system. However, it is noted that the HY, defined by the amount of hydrogen produced per substrate consumed, is more dependent upon the microbial properties, substrate type, and environmental conditions rather than the reactor configurations. In fact, for dark-fermentation processes, HYs obtained with different systems are rather inconsistent so far and mostly no greater than those achieved with CSTRs (continuously stirred tank reactors). Thus, there is no reason to think that the reactor type would essentially influence the HY in dark-fermentation systems, and a comparison of these reactors here shall mainly be based on their HRPs. For the phototrophic and MEC (microbial electrolysis cells) hydrogen production processes, however, the HY is usually used for reactor evaluation because of the fewer microbial species and substrates involved as well as the relatively low HPR value of such systems. In addition, the operating stability is also a critical factor to be considered for the biological hydrogen production systems.
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