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Characterizing nano-scale electrocatalysis during partial oxidation of methane.

ABSTRACT: Electrochemical analysis allows in situ characterization of solid oxide electrochemical cells (SOCs) under operating conditions. However, the SOCs that have been analyzed in this way have ill-defined or uncommon microstructures in terms of porosity and tortuosity. Therefore, the nano-scale characterization of SOCs with respect to three-phase boundaries has been hindered. We introduce novel in situ electrochemical analysis for SOCs that uses combined solid electrolyte potentiometry (SEP) and impedance measurements. This method is employed to investigate the oscillatory behavior of a porous Ni-yttria-stabilized zirconia (YSZ) anode during the partial oxidation of methane under ambient pressure at 800°C. The cyclic oxidation and reduction of nickel induces the oscillatory behavior in the impedance and electrode potential. The in situ characterization of the nickel surface suggests that the oxidation of the nickel occurs predominantly at the two-phase boundaries, whereas the nickel at the three-phase boundaries remains in the metallic state during the cyclic redox reaction.

SUBMITTER: Lee D

PROVIDER: S-EPMC3909905 | biostudies-other | 2014

REPOSITORIES: biostudies-other

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Characterizing nano-scale electrocatalysis during partial oxidation of methane.

Lee Daehee D Kim Dongha D Kim Joosun J Moon Jooho J

Scientific reports 20140203

Electrochemical analysis allows in situ characterization of solid oxide electrochemical cells (SOCs) under operating conditions. However, the SOCs that have been analyzed in this way have ill-defined or uncommon microstructures in terms of porosity and tortuosity. Therefore, the nano-scale characterization of SOCs with respect to three-phase boundaries has been hindered. We introduce novel in situ electrochemical analysis for SOCs that uses combined solid electrolyte potentiometry (SEP) and impe ...[more]

PMID: 24487242

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Project description:In this study, we investigated Mn3+-cycling microbial populations enriched from Lake Matano, Indonesia using metagenomics and metaproteomics. Lake Matano contains an active Mn cycle that links the oxic-anoxic interface with anoxic deep waters that are enriched in iron and manganese, and depleted in sulfate, phosphate, and oxidized nitrogen (Crowe et al., 2008; Jones et al., 2011). Sediments were incubated with sequential transfers for ~1 year with Mn3+ as the sole electron acceptor and methane as organic carbon until achieving sediment-free conditions. Here we investigate this novel species of Dechloromonas (Betaproteobacteria), “Candidatus Dechloromonas occultata,” which was the dominant population in enrichment cultures with active Mn3+ reduction. “Ca. D. occultata” expressed electron conduits related to those involved in Fe2+ oxidation (Mto-like), as well as a novel cytochrome c-rich gene cluster putatively involved in extracellular electron transfer, and an atypical nitrous oxide reductase. According to ribosomal counts, Dechloromonas outnumber Geobacter. In terms of functional genes, Dechloromonas expresses a wider variety and number of genes. Dechloromonas therefore seems to have a (selective?) advantage over Geobacter. Previous experiments revealed that Dechloromonas express nitrogen regulators, reductases and scavenging genes, as well as many carbon central metabolic pathways, and aromatic carbon degradation pathways. Dechloromonas is a beta proteobacteria, and these are "experts" in nitrogen metabolism. Geobacter, on the other hand, is well known for carbon degradation. Our previous experiments lead to our hypothesis that Dechloromonas is more active because they are more successful at acquiring nitrogen, a limiting nutrient for Geobacter. This would further suggest that carbon is not the limiting nutrient. We will test 2 hypotheses with the next suite of experiments 1) pyrophosphate supports the community, by allowing carbon fixation , 2)Dechloromonas has a (selective?) advantage over Geobacter. To test this hypothesis, bioreactors will be used to grow biotriplicate cultures of (1)- CH4 vs. pyrophosphate and (2)-CH4 vs. Mn(III) pyrophosphate. Here we have analyzed whole cell pellets using gas phase fractionations on the Q Exactive. Are Dechloromonas capable of out-competing Geobacter when grown in media with methane as the only carbon source bioreactors because they are capable of acquiring more nitrogen? Source of inoculum. Lake Matano is a metal-rich, ancient ocean analog (Crowe et al. 2011, Jones et al. 2011). Organic carbon in Lake Matano is mostly mineralized via methanogenesis before reaching the iron-rich sediments, limiting organic matter bioavailability for metal-reducers (Kuntz et al. 2015). A 15-cm sediment core from 200 m water depth in Lake Matano, Sulawesi Island, Indonesia (02°26′27.1′′S, 121°15′12.3′′E; in situ sediment temperature ~27°C) was sampled in November 2014 and sub-sampled at 5 cm increments. Sediments were sealed in gas-tight Mylar bags with no headspace (Hansen et al. 2000) and stored at 4°C until incubations began in December 2015.

Dataset Information

Characterizing nano-scale electrocatalysis during partial oxidation of methane.

Publications

Characterizing nano-scale electrocatalysis during partial oxidation of methane.

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