Intercalating cobalt cation to Co9S8 interlayer for highly efficient and stable electrocatalytic hydrogen evolution

Non-noble metal based electrocatalysts for hydrogen evolution reactions hold great potential for commercial applications. However, effective design strategies are highly needed to manipulate the catalyst structures for high activity and...

Hydrogen transport property of polymer-derived cobalt cation-doped amorphous silica

The effect of the local structure of Co-doped amorphous silica on the hydrogen transport property was studied with the aim to improve the high-temperature hydrogen-permselectivity of microporous amorphous silica-based membranes.

Cobalt Resistance via Detoxification and Mineralization in the Iron-Reducing Bacterium Geobacter sulfurreducens

Bacteria in the genus Geobacter thrive in iron- and manganese-rich environments where the divalent cobalt cation (CoII) accumulates to potentially toxic concentrations. Consistent with selective pressure from environmental exposure, the model laboratory representative Geobacter sulfurreducens grew with CoCl2 concentrations (1 mM) typically used to enrich for metal-resistant bacteria from contaminated sites. We reconstructed from genomic data canonical pathways for CoII import and assimilation into cofactors (cobamides) that support the growth of numerous syntrophic partners. We also identified several metal efflux pumps, including one that was specifically upregulated by CoII. Cells acclimated to metal stress by downregulating non-essential proteins with metals and thiol groups that CoII preferentially targets. They also activated sensory and regulatory proteins involved in detoxification as well as pathways for protein and DNA repair. In addition, G. sulfurreducens upregulated respiratory chains that could have contributed to the reductive mineralization of the metal on the cell surface. Transcriptomic evidence also revealed pathways for cell envelope modification that increased metal resistance and promoted cell-cell aggregation and biofilm formation in stationary phase. These complex adaptive responses confer on Geobacter a competitive advantage for growth in metal-rich environments that are essential to the sustainability of cobamide-dependent microbiomes and the sequestration of the metal in hitherto unknown biomineralization reactions.

Oxygen Adsorption and Activation on Cobalt Center in Modified Keggin Anion-DFT Calculations

The influence of the cobalt cation geometric environment on catalytic activity, namely, oxygen adsorption and its activation, was investigated by exploring two groups of systems. The first group was formed by cobalt cation complexes, in which the Co2+ was surrounded by water-H2O or acetonitrile-CH3CN solvent molecules. This represents heteropolyacids salts (ConH3-nPW(Mo)12O40), where the Co2+ acts as a cation that compensates for the negative charge of the Keggin anion and is typically surrounded by solvent molecules in that system. The second group consisted of tungsten or molybdenum Keggin anions (H5PW11CoO39 and H5PMo11CoO39), having the Co2+ cation incorporated into the anion framework, in the position of one addenda atom. Detailed NOCV (Natural Orbitals for Chemical Valence) analysis showed that, for all studied systems, the σ-donation and σ-backdonation active channels of the electron transfer were responsible for the creation of a single Co-OO bond. Depending on the chemical/geometrical environment of the Co2+ cation, the different quantities of electrons were flown from the Co2+ 3d orbital to the π* antibonding molecular orbitals of the oxygen ligand, as well as in the opposite direction. In molybdenum and tungsten heteropolyacids, modified by Co2+ in the position of the addenda atom, activation of O2 was supported by a π-polarization process. Calculated data show that the oxygen molecule activation changed in the following order: H5PMo11CoO39 = H5PW11CoO39 > Co(CH3CN)52+ > Co(H2O)52+.

Role of Water in Diethyl Ether Dehydration Reaction

The study examined catalytic conversion of diethyl ether in a gas phase in the static system on the synthetic mordenite (NaM) and the mordenite which the bivalent cobalt cation was introduced into (CoM). The reaction was observed in the temperature range from 424 K to 653 K, and the reaction products on both catalysts were ethene and water, and on NaM a small quantity of butene.The reaction of diethyl ether dehydration in the observed temperature interval is accelerate in time. The initial reaction is registered at the very beginning of the reaction followed by the water occurrence. The water originating from the reaction is generated on the surface of the zeolite catalyst the active centers that is favorable for the dehydration reaction. With the temperature growth the initial period on NaM catalyst gradually disappears and the reaction becomes the first order reaction (temperature is 653 K), while on CoM catalyst the initial period is registered at all observed temperatures. The explanation of the role of water in the occurrence of active centers needed for diethyl ether hydrolysis was obtained by experiments in which water was also added to the reaction mixture of diethyl ether – catalyst.