Influence of Composition of Nickel‐Iron Nanoparticles for Abiotic CO₂ Conversion to Early Prebiotic Organics

Abstract

Abiotic synthesis of formate and short hydrocarbons takes place in serpentinizing vents where some members of vent microbial communities live on abiotic formate as their main carbon source. To better understand the catalytic properties of NiÀ Fe minerals that naturally exist in hydrothermal vents, we have investigated the ability of synthetic NiÀ Fe based nanoparticular solids to catalyze the H 2 -dependent reduction of CO 2 , the first step required for the beginning of prebiotic chemistry. Mono and bimetallic NiÀ Fe nanoparticles with varied Ni-to-Fe ratios transform CO 2 and H 2 into intermediates and products of the acetylcoenzyme A pathway-formate, acetate, and pyruvatein mM range under mild hydrothermal conditions. Furthermore, NiÀ Fe catalysts converted CO 2 to similar products without molecular H 2 by using water as a hydrogen source. Both CO 2 chemisorption analysis and post-reaction characterization of materials indicate that Ni and Fe metals play complementary roles for CO 2 fixation.

Direct Synthesis of Formamide from CO2 and H2O with Nickel–Iron Nitride Heterostructures under Mild Hydrothermal Conditions

“…It is known that formate can be obtained from CO 2 via autocatalysis mechanisms in water over transition metals . A similar phenomenon has also been observed, and H 2 O was transformed into formate and acetate over metallic Ni 3 Fe nanoparticles . This phenomenon and the formation pathway of nitrogen-containing compounds is discussed below in detail.…”

“…The reduction of synthesized metal oxides was performed with 10% H 2 /Ar gas flow (total flow rate: 100 mL/min) at 500 °C for 2 h to obtain reduced metal nanoparticles (ramping rate is 2 °C/min). In order to prevent the complete oxidation of metal nanoparticles after H 2 reduction, the surface passivation process with air/Ar gas flow (100 mL/min, 2% air) was performed at room temperature for 1 h. 38 Ni−Fe nitrides were obtained via the ammonolysis method. After H 2 reduction, metal powders were subjected to ammonia treatment in the tube furnace.…”

“…The formation of formate in hydrothermal vents is driven by the serpentinization process, which yields H 2 for the reduction of CO 2 and its dissolved forms . The oxidized carbon species are presumed to be the ultimate source of carbon for the abiotic synthesis of organic molecules. , Several studies report the formation of formate from CO 2 with hydrothermal minerals under mild hydrothermal vent conditions. − The formation of formate and acetate occurs via the gas-phase H 2 -dependent CO 2 reduction over silica-supported Co nanoparticles, and Ni–Fe nanoparticles are able to reduce CO 2 to the free intermediates of the acetyl-CoA pathway of CO 2 fixationformate, acetate, and pyruvateunder mild hydrothermal conditions in the absence of the synthetic H 2 . The conditions of serpentinizing systems are reducing enough to have stable forms of Ni–Fe alloys and their native metal forms. , Awaruite (Ni 3 Fe) is known to exist in H 2 -rich serpentinizing systems. , Furthermore, a recent study by Peters et al reported that nickel–iron-containing meteoritic catalyst (Campo del Cielo) yields methanol, ethanol, acetaldehyde, and alkanes from the hydrogenation of CO 2 under hydrothermal conditions …”

Quantifying Catalysis at the Origin of Life**

“…Schemes 1 and 2 outline several studies that have used various batch and flow conditions to fix CO 2 into organic molecules. Under pressurized batch conditions, supported silica Co afforded the transformation of CO 2 to methane, acetate and methanol, [14] Fe−Ni nanoparticles facilitated the transformation of CO 2 to formate, acetate and pyruvate, [15,16] and iron nanoparticles mediated the reduction of CO 2 with H 2 to formic acid and acetic acid [17] . Fe powder in water [18] (without another reductant) likewise facilitates this transformation, as does a variety of iron‐based minerals [19] to generate several additional reduction products (including acetate, pyruvate, and citramalate).…”

“…Another method for the demonstration of heterogeneous catalysis is the ‘hot filtration test’ whereby heterogeneous particles are removed partway through a reaction and the progress of that reaction is compared to a reaction run where the heterogenous material remains throughout the duration of the reaction. Such a test was completed with the Fe−Ni particle mediated production of pyruvate from CO 2 ; when the reaction was filtered after 8 h, and the supernatant was allowed to continue reacting, the yield only negligibly increased when checked again after 24 h. The yield significantly increased when the mineral was left in reactor for the full 24 h [15] …”