Understanding abiotic carbon fixation offers insights into early Earth’s carbon cycles and the emergence of life in terrestrial hot springs. Iron sulfide (FeS), which resembles cofactors in metabolic enzymes, may play a key role in catalyzing prebiotic synthesis. However, the specific role of FeS in carbon fixation under these conditions has yet to be thoroughly explored.
A new study led by the Chinese Academy of Sciences investigates the catalytic properties of iron sulfide (FeS), both pure and doped with titanium (Ti), nickel (Ni), manganese (Mn), and cobalt (Co). The study explores FeS’s ability to drive hydrogen (H2)- powered carbon dioxide (CO2) reduction to methanol under simulated hot spring vapor-zone conditions. The researchers used an anaerobic flow chamber connected to a gas chromatograph to analyze the process.
The study suggests that the sulfides may have catalyzed the reduction of gaseous carbon dioxide into prebiotic organic molecules via nonenzymatic pathways. It offers new insights into Earth’s early carbon cycles and prebiotic chemical reactions.
Iron sulfides, abundant in early Earth’s hydrothermal systems, may have facilitated essential prebiotic chemical reactions, similar to the function of cofactors in modern metabolic systems. Previous studies on iron sulfides and the origin of life have focused primarily on deep-sea alkaline hydrothermal vents, which provide favorable conditions like high temperature, pressure, pH gradients, and hydrogen (H₂) from serpentinization—factors thought to support prebiotic carbon fixation.
However, some scientists have proposed terrestrial hot springs as another plausible setting for life’s origins due to their rich mineral content, diverse chemicals, and abundant sunlight.
To investigate the role of iron sulfides in terrestrial prebiotic carbon fixation, the research team synthesized nanoscale iron sulfides from mackinawite, including both pure iron sulfide and iron sulfides doped with elements commonly found in hot springs, such as manganese, nickel, titanium, and cobalt.
Their experiments demonstrated that these iron sulfides could catalyze the hydrogen (H₂)-driven reduction of carbon dioxide (CO₂) into methanol at temperatures between 80 and 120 °C and atmospheric pressure. Gas chromatography was used to measure and quantify the methanol production.
The study found that manganese-doped iron sulfides exhibited significantly higher catalytic activity at 120 °C, with the reaction further enhanced by both UV-visible (300–720 nm) and UV-enhanced (200–600 nm) light.
This suggests that sunlight could have played a role in driving the H₂-driven CO₂ reduction by facilitating chemical processes. Adding water vapor also boosted catalytic activity, supporting the idea that vapor-laden terrestrial hot springs may have been key sites for nonenzymatic organic synthesis on early Earth.
The team used diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) to explore the reaction mechanism for in-situ analysis. Results indicated that the process likely follows the reverse water-gas shift (RWGS) pathway, where CO₂ is first reduced to carbon monoxide (CO), which is then hydrogenated to form methanol.
Density functional theory (DFT) calculations showed that manganese doping lowered the reaction’s activation energy and introduced efficient electron transfer sites, enhancing the reaction’s efficiency. The redox properties of iron sulfides make them functionally similar to modern metabolic enzymes, offering a potential chemical foundation for prebiotic carbon fixation.
Journal Reference:
- Nan, J., Luo, S., Tran, Q.P. et al. Iron sulfide-catalyzed gaseous CO2 reduction and prebiotic carbon fixation in terrestrial hot springs. Nat Commun 15, 10280 (2024). DOI: 10.1038/s41467-024-54062-y