title: Comparison of Nonprecious Metal Cathode Materials for Methane Production by Electromethanogenesis.
abstract: In methanogenic microbial electrolysis cells (MMCs), CO2is reduced to methane using a methanogenic biofilm on the cathode by either direct electron transfer or evolved hydrogen. To optimize methane generation, we examined several cathode materials: plain graphite blocks, graphite blocks coated with carbon black or carbon black containing metals (platinum, stainless steel or nickel) or insoluble minerals (ferrihydrite, magnetite, iron sulfide, or molybdenum disulfide), and carbon fiber brushes. Assuming a stoichiometric ratio of hydrogen (abiotic):methane (biotic) of 4:1, methane production with platinum could be explained solely by hydrogen production. For most other materials, however, abiotic hydrogen production rates were insufficient to explain methane production. At -600 mV, platinum on carbon black had the highest abiotic hydrogen gas formation rate (1600 ± 200 nmol cm-3d-1) and the highest biotic methane production rate (250 ± 90 nmol cm-3d-1). At -550 mV, plain graphite (76 nmol cm-3d-1) performed similarly to platinum (73 nmol cm-3d-1). Coulombic recoveries, based on the measured current and evolved gas, were initially greater than 100% for all materials except platinum, suggesting that cathodic corrosion also contributed to electromethanogenic gas production.
authors.affiliation: Department of Civil and Environmental Engineering, The Pennsylvania State University , University Park, Pennsylvania 16802, United States.
authors.forename: Michael
authors.initials: M
authors.lastname: Siegert
authors.affiliation: Department of Civil and Environmental Engineering, The Pennsylvania State University , University Park, Pennsylvania 16802, United States.
authors.forename: Matthew D
authors.initials: MD
authors.lastname: Yates
authors.affiliation: Department of Civil and Environmental Engineering, The Pennsylvania State University , University Park, Pennsylvania 16802, United States ; Department of Civil and Environmental Engineering, Syracuse University , Syracuse, New York 13244, United States.
authors.forename: Douglas F
authors.initials: DF
authors.lastname: Call
authors.affiliation: Department of Civil and Environmental Engineering, The Pennsylvania State University , University Park, Pennsylvania 16802, United States.
authors.forename: Xiuping
authors.initials: X
authors.lastname: Zhu
authors.affiliation: Department of Civil and Environmental Engineering and Department of Chemical Engineering, Stanford University , Stanford, California 94305, United States.
authors.forename: Alfred
authors.initials: A
authors.lastname: Spormann
authors.affiliation: Department of Civil and Environmental Engineering, The Pennsylvania State University , University Park, Pennsylvania 16802, United States.
authors.forename: Bruce E
authors.initials: BE
authors.lastname: Logan
keywords: Biocathode; Carbon black; Carbon capturing and sequestration; Graphite; Microbial electrolysis cell; Microbially influenced corrosion; Polyacrylonitrile; Power-to-gas
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