Interface-Engineered Methanogenic Nanobiohybrids Redirect Hydrogen Flux for Efficient CO₂ Fixation.

Area of Science:

• Biohybrid systems
• Nanomaterials science
• Microbial electrochemistry

Background:

• Nanobiohybrids integrate synthetic materials with microbes for applications like CO2 fixation.
• Inefficient electron transfer at interfaces limits current nanobiohybrid systems.
• Zerovalent iron (nZVI) is a strong reductant but suffers from hydrogen release and toxicity.

Purpose of the Study:

• To engineer a novel nanobiohybrid system for enhanced CO2 fixation and methane production.
• To overcome limitations of interfacial electron delivery and hydrogen evolution in nZVI-microbe systems.
• To develop a strategy for controlled electron and proton flux in biohybrid systems.

Main Methods:

• Fabrication of silicate-modified nZVI (Si-nZVI) nanoparticles.
• Co-culturing Si-nZVI with the methanogen *Methanosarcina barkeri*.
• Spectroscopic, biochemical, computational, and transcriptomic analyses to elucidate mechanisms.

Main Results:

• Achieved near-theoretical methane yields (4256 μmol g^-1 Fe) from CO2 with 99.5% selectivity.
• Demonstrated that surface Si-O bonds stabilize reactive hydrogen, directing flux to methanogenesis.
• Showcased reduced iron corrosion and improved microbial fitness under anaerobic conditions.

Conclusions:

• Surface modification of nZVI with silicate controls hydrogen speciation for efficient CO2 biomethanation.
• This engineered interface enhances electron and proton transfer, bypassing wasteful hydrogen production.
• The Si-nZVI/*M. barkeri* system presents a promising strategy for CO2 utilization and biogas upgrading.