Robust and biocompatible catalysts for efficient hydrogen-driven microbial electrosynthesis

Frauke Kracke,Mckenzie A Hubert,Karen Maegaard,Thomas F Jaramillo,Joerg S Deutzmann,Andrew Barnabas Wong,Alfred M Spormann,Christopher Hahn

doi:10.1038/s42004-019-0145-0

Frauke Kracke, Mckenzie A Hubert + Show 6 more

Open Access

https://doi.org/10.1038/s42004-019-0145-0

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Abstract

CO2 reduction by combined electro- and bio-catalytic reactions is a promising technology platform for sustainable production of chemicals from CO2 and electricity. While heterogeneous electrocatalysts can reduce CO2 to a variety of organic compounds at relatively high reaction rates, these catalysts have limitations achieving high selectivity for any single product beyond CO. Conversely, microbial CO2 reduction pathways proceed at high selectivity; however, the rates at bio-cathodes using direct electron supply via electricity are commonly limiting. Here we demonstrate the use of non-precious metal cathodes that produce hydrogen in situ to support microbial CO2 reduction to C1 and C2 compounds. CoP, MoS2 and NiMo cathodes perform durable hydrogen evolution under biologically relevant conditions, and the integrated system achieves coulombic efficiencies close to 100% without accumulating hydrogen. Moreover, the one-reactor hybrid platform is successfully used for efficient acetate production from electricity and CO2 by microbes previously reported to be inactive in bioelectrochemical systems.

Highlights

CO2 reduction by combined electro- and bio-catalytic reactions is a promising technology platform for sustainable production of chemicals from CO2 and electricity
While a direct comparison to other stateof-the-art catalysts is challenging due to the aforementioned factors, the results clearly indicate that all tested catalysts can achieve favorable hydrogen production rates for biointegration, with the nickel–molybdenum alloy (NiMo) alloy presenting the most promising material under the conditions tested
The observed long-term stability of H2 production on CoP, MoS2, and NiMo cathodes, despite the accumulation of organic and inorganic material on the electrode surface, demonstrates the potential of this technology to be usable at industrially relevant time scales

Summary

Introduction

CO2 reduction by combined electro- and bio-catalytic reactions is a promising technology platform for sustainable production of chemicals from CO2 and electricity. Several industrially relevant chemicals such as methane, acetic acid, butyric acid, isobutyric acid, hexanoic acid, ethanol, isopropanol, butanol, isobutanol, and hexanol have been shown to be produced via microbial electrosynthesis from CO2 and electricity[19,20,21,22,23]. These processes currently remain limited by low direct electron uptake rates from the cathode and by a limited number of microbes that are able to directly acquire electrons from solid state electrodes for CO2 reduction[18,24]. Severe deactivation of inorganic catalysts by microbial growth media components was observed in previous studies[33] as well as toxic effects towards the microorganisms caused by dissolution of the cathode material[34]

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