Efficient Hydrogen Delivery for Microbial Electrosynthesis via 3D-Printed Cathodes

Journal Article · 02 August 2021 · Frontiers in Microbiology

DOI: https://doi.org/10.3389/fmicb.2021.696473 · OSTI ID:1821269

Kracke, Frauke ^[1]; Deutzmann, Jörg S. ^[1]; Jayathilake, Buddhinie S. ^[2]; Pang, Simon H. ^[2]; Chandrasekaran, Swetha ^[2]; Baker, Sarah E. ^[2]; Spormann, Alfred M. ^[1]

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1. Stanford Univ., CA (United States)
2. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

The efficient delivery of electrochemically in situ produced H₂ can be a key advantage of microbial electrosynthesis over traditional gas fermentation. However, the technical details of how to supply large amounts of electric current per volume in a biocompatible manner remain unresolved. Here, we explored for the first time the flexibility of complex 3D-printed custom electrodes to fine tune H₂ delivery during microbial electrosynthesis. Using a model system for H₂-mediated electromethanogenesis comprised of 3D fabricated carbon aerogel cathodes plated with nickel-molybdenum and Methanococcus maripaludis, we showed that novel 3D-printed cathodes facilitated sustained and efficient electromethanogenesis from electricity and CO₂ at an unprecedented volumetric production rate of 2.2 L_CH4 /L_catholyte/day and at a coulombic efficiency of 99%. Importantly, our experiments revealed that the efficiency of this process strongly depends on the current density. At identical total current supplied, larger surface area cathodes enabled higher methane production and minimized escape of H₂. Specifically, low current density (<1 mA/cm²) enabled by high surface area cathodes was found to be critical for fast start-up times of the microbial culture, stable steady state performance, and high coulombic efficiencies. Our data demonstrate that 3D-printing of electrodes presents a promising design tool to mitigate effects of bubble formation and local pH gradients within the boundary layer and, thus, resolve key critical limitations for in situ electron delivery in microbial electrosynthesis.

• Research Organization: Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)
• Sponsoring Organization: Southern California Gas Company; USDOE National Nuclear Security Administration (NNSA); USDOE Office of Energy Efficiency and Renewable Energy (EERE), Transportation Office. Bioenergy Technologies Office
• Grant/Contract Number: AC52-07NA27344
• OSTI ID: 1821269
• Report Number(s): LLNL-JRNL--821387; 1033367
• Journal Information: Frontiers in Microbiology, Journal Name: Frontiers in Microbiology Vol. 12; ISSN 1664-302X
• Publisher: Frontiers Research FoundationCopyright Statement
• Country of Publication: United States
• Language: English