Assessment of the microbial community in the cathode compartment of a plant microbial fuel cell

Introduction: In plant microbial fuel cells (plant-MFCs) living plants and microorganisms form an electrochemical unit able to produce clean and sustainable electricity from solar energy. It is reasonable to assume that besides the bacteria in the anode compartment also the cathode compartment plays a crucial role for a stable high current producing plant-MFC. In this study we aim to identify dominant bacterial species in the cathode compartment of the plant-MFC

Monophyletic group of unclassified γ-Proteobacteria dominates in mixed culture biofilm of high-performing oxygen reducing biocathode

International audienceSeveral mixed microbial communities have been reported to show robust bioelectrocatalysis of oxygen reduction over time at applicable operation conditions. However, clarification of electron transfer mechanism(s) and identification of essential micro-organisms have not been realised. Therefore, the objective of this study was to shape oxygen reducing biocathodes with different microbial communities by means of surface modification using the electrochemical reduction of two different diazonium salts in order to discuss the relation of microbial composition and performance. The resulting oxygen reducing mixed culture biocathodes had complex bacterial biofilms variable in size and shape as observed by confocal and electron microscopy. Sequence analysis of ribosomal 16S rDNA revealed a putative correlation between the abundance of certain microbiota and biocathode performance. The best performing biocathode developed on the unmodified graphite electrode and reached a high current density for oxygen reducing biocathodes at neutral pH (0.9A/m(2)). This correlated with the highest domination (60.7%) of a monophyletic group of unclassified γ-Proteobacteria. These results corroborate earlier reports by other groups, however, higher current densities and higher presence of these unclassified bacteria were observed in this work. Therefore, members of this group are likely key-players for highly performing oxygen reducing biocathodes.[on SciFinder (R)

Struktur-Eigenschafts-Beziehungen von Verbindungen mit Pyrit- und Shanditstruktur mit Metall-Halbleiter-Übergang in InSnCo3S2

Ziel der Arbeit ist es theoretische Rechnungen mit experimentellen Ergebnissen zu korrelieren, um Stabilitäten und Strukturen zu verstehen damit man ihre Eigenschaften für mögliche Anwendungen beeinflussen zu können. Eigenschaften von Verbindungen sind über ihre elektronische Struktur definiert. Man kann sie über Substitution oder Dotierung beeinflussen. "Electronic design" ist ein grundlegendes Prinzip in der Materialwissenschaft. Durch sie kann man elektrische und magnetische Eigenschaften einer Ausgangsverbindung gezielt beeinflussen. In der Arbeit wurden Verbindungen mit Pyrit Struktur und die Verbindung Sn2Co3S2 und von diesen abgeleitete Verbindungen untersucht. Deren elektronische und kristallografische Struktur sind hoch flexibel und Sn2Co3S2 ist ein halbmetallischer Ferromagnet. Durch die Substitution von Indium gegen Zinn erhält man einen Halbleiter aufgrund der Ausordnung von Indium und Zinn. Bei der Dotierung von Selen gegen Schwefel tritt eine Veränderung des Magnetismus auf. Um diese Effekte zu verstehen wurden Magnetische-, XRD-, Neutronen- und Leitfähigkeitsmessungen durchgeführt genauso wie DFT Rechnungen im Reziproken- und Realraum

Origin and effect of In–Sn ordering in InSnCo3S2: a neutron diffraction and DFT study

The solid solution In2−xSnxCo3S2 is attractive due to a variety of interesting properties depending on the In/Sn content, i.e. half metal ferromagnetic Sn2Co3S2, low dimensional metal In2Co3S2, and semiconducting thermoelectric InSnCo3S2. For the latter, crystal structure effects and a metal to insulator transition are not only related to electron counting but also to ordering of In and Sn within and between Co Kagomé nets. These observations have not been adequately understood to date. The degree of ordering is now evaluated from neutron diffraction data to distinguish In and Sn. The origin and effects on crystal and electronic structures are studied by DFT calculations on a superstructure model. Relations of local bonding (electron localization function ELF and Bader's AIM theory), In/Sn site preference, crystal structure distortions, and the opening of the gap are explored. Results are generalised from predictions on isoelectronic compounds