Surface modified copper foam with cobalt phthalocyanine carbon nanotube hybrids for tuning CO2 reduction reaction products.

The CO2 reduction reaction (CO2RR) is a feasible way to convert this greenhouse gas into molecules of industrial interest. Herein we present the modification of the Cu foam cathode using molecular catalyst hybrid from cobalt phthalocyanine (CoPc) to increase selectivity and stability towards CO2RR products in a flow cell setup.

Testing Abiotic Reduction of NAD+ Directly Mediated by Iron/Sulfur Minerals.

Life emerged in a geochemical context, possibly in the midst of mineral substrates. However, it is not known to what extent minerals and dissolved inorganic ions could have facilitated the evolution of biochemical reactions. Herein, we have experimentally shown that iron sulfide minerals can act as electron transfer agents for the reduction of the ubiquitous biological protein cofactor nicotinamide adenine dinucleotide (NAD+) under anaerobic prebiotic conditions, observing the NAD+/NADH redox transition by using ultraviolet-visible spectroscopy and 1H nuclear magnetic resonance. This reaction was mediated with iron sulfide minerals, which were likely abundant on early Earth in seafloor and hydrothermal settings; and the NAD+/NADH redox reaction occurred in the absence of UV light, peptide ligand(s), or dissolved mediators. To better understand this reaction, thermodynamic modeling was also performed. The ability of an iron sulfide mineral to transfer electrons to a biochemical cofactor that is found in every living cell demonstrates how geologic materials could have played a direct role in the evolution of certain cofactor-driven metabolic pathways.

Room-temperature cycling of metal fluoride electrodes: Liquid electrolytes for high-energy fluoride ion cells.

Fluoride ion batteries are potential "next-generation" electrochemical storage devices that offer high energy density. At present, such batteries are limited to operation at high temperatures because suitable fluoride ion-conducting electrolytes are known only in the solid state. We report a liquid fluoride ion-conducting electrolyte with high ionic conductivity, wide operating voltage, and robust chemical stability based on dry tetraalkylammonium fluoride salts in ether solvents. Pairing this liquid electrolyte with a copper-lanthanum trifluoride (Cu@LaF3) core-shell cathode, we demonstrate reversible fluorination and defluorination reactions in a fluoride ion electrochemical cell cycled at room temperature. Fluoride ion-mediated electrochemistry offers a pathway toward developing capacities beyond that of lithium ion technology.

Geoelectrodes and Fuel Cells for Simulating Hydrothermal Vent Environments.

Gradients generated in hydrothermal systems provide a significant source of free energy for chemosynthetic life and may play a role in present-day habitability on ocean worlds. Electron/proton/ion gradients, particularly in the context of hydrothermal chimney structures, may also be relevant to the origins of life on Earth. Hydrothermal vents are similar in some ways to typical fuel cell devices: redox/pH gradients between seawater and hydrothermal fluid are analogous to the fuel cell oxidant and fuel reservoirs; the porous chimney wall is analogous to a separator or ion-exchange membrane and is also a conductive path for electrons; and the hydrothermal minerals are analogous to electrode catalysts. The modular and scalable characteristics of fuel cell systems make for a convenient planetary geology test bed in which geologically relevant components may be assembled and investigated in a controlled simulation environment. We have performed fuel cell experiments and electrochemical studies to better understand the catalytic potential of seafloor minerals and vent chimneys, using samples from a black smoker vent chimney as an initial demonstration. In a fuel cell with Na+-conducting Nafion® membranes and liquid fuel/oxidant reservoirs (simulating the vent environment), the black smoker mineral catalyst in the membrane electrode assembly was effective in reducing O2 and oxidizing sulfide. In a H2/O2 polymer electrolyte membrane (PEM) fuel cell with H+-conducting Nafion membranes, the black smoker catalyst was effective in reducing O2 but not in oxidizing H2. These fuel cell experiments accurately simulated the redox reactions that could occur in a geological setting with this particular catalyst, and also tested whether the minerals are sufficiently active to replace a commercial fuel cell catalyst. Similar experiments with other geocatalysts could be utilized to test which redox reactions could be driven in other hydrothermal systems, including hypothesized vent systems on other worlds.