Effect of Alkali- and Alkaline-Earth-Metal Promoters on Silica-Supported Co-Fe Alloy for Autocatalytic CO2 Fixation

Hydrothermal vents harbor numerous microbial communities rich in reduced carbon species such as formate, acetate, and hydrocarbons. Such essential chemicals for life are produced by H2 -dependent CO2 reduction, where serpentinization provides continuous H2 and thermal energy. Here, we show that silica-supported bimetallic Co-Fe alloys, naturally occurring minerals around serpentinite, can convert CO2 and H2 O to key metabolic intermediates of the acetyl coenzyme A pathway such as formate (up to 72 mM), acetate, and pyruvate under mild hydrothermal vent conditions. Long-chain hydrocarbons up to C6 including propene are also detected, just as in the Lost City hydrothermal field. The effects of promoters on structural properties and catalytic functionalities of the Co-Fe alloy are systematically investigated by incorporating a series of alkali and alkaline earth metals including Na, Mg, K, and Ca. Alkali and alkaline earth metals resulted in higher formate concentrations when dissolved in water and increased reaction pH, while alkaline earth metals also favored the formation of insoluble hydroxides and carbonates similar to the constituent minerals of the chimneys at the Lost City hydrothermal fields.

Facile Organometallic Synthesis of Fe-Based Nanomaterials by Hot Injection Reaction

Fe-based colloids with a core/shell structure consisting of metallic iron and iron oxide were synthesized by a facile hot injection reaction of iron pentacarbonyl in a multi-surfactant mixture. The size of the colloidal particles was affected by the reaction temperature and the results demonstrated that their stability against complete oxidation related to their size. The crystal structure and the morphology were identified by powder X-ray diffraction and transmission electron microscopy, while the magnetic properties were studied at room temperature with a vibrating sample magnetometer. The injection temperature plays a very crucial role and higher temperatures enhance the stability and the resistance against oxidation. For the case of injection at 315 °C, the nanoparticles had around a 10 nm mean diameter and revealed 132 emu/g. Remarkably, a stable dispersion was created due to the colloids' surface functionalization in a nonpolar solvent.