Project Details
Projekt
Magnetite anodes to inhibit oxygen production and to circumvent membranes in microbial electrosynthesis
Subject Area
Biological Process Engineering
Mineralogy, Petrology and Geochemistry
Mineralogy, Petrology and Geochemistry
Term
since 2021
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 445506379
Microbial electrosynthesis is a newly emerging biosynthesis strategy, which has shown great potential in producing value-added chemicals and fuels, while at the same time reducing environmental carbon dioxide concentration. The cathode performance during microbial electrosynthesis has been largely improved in the past years, due to its direct or mediated electron transfer interactions with anaerobic microbes. However, so far, the anode performance has not been given enough attention, despite its importance in closing the electric circuit and bearing the electrical energy to initiate the electrosynthesis. The most common product at the anode is oxygen, which is toxic to the anaerobic autotrophs that engage in microbial electrosynthesis. To limit oxygen toxicity, a membrane is used to separate the anode and the cathode chamber to avoid the contact between microbes and oxygen. Application of a membrane not only increases the maintenance cost, but also comprises the production efficiency by introducing an extra internal resistance. Further, the electro-osmotic flux occurring within the membrane inevitably drives some transfer of oxygen to the catholyte. Therefore, the overarching goal of this proposal is to develop a new anode system to simultaneously inhibit oxygen evolution and circumvent the membrane application. This would ultimately allow the microbial electrosynthesis to proceed in a single chamber. Environmental iron minerals are highly redox-active and naturally abundant. Specifically, we propose here that magnetite (Fe3O4), which is a mixed valent iron mineral (i.e., contains both Fe(II) and Fe(III)), could be used as an alternative anode (electrode) material due to its thermodynamic favorability in proceeding oxidation than oxygen evolution at the anode. We will specifically focus on: (1) assessing magnetite anode stability in inhibiting oxygen formation; (2) investigating the in-situ reversibility of magnetite anode to sustain long-term microbial electrosynthesis; and (3) improving the conductivity and regeneration of the magnetite anode to facilitate the application of magnetite anode in industrial-scale bioelectrochemical systems. We will use Methanothermobacter thermoautotrophicus and Clostridium ljungdahlii as anaerobic microbes to quantify the oxygen inhibiting efficiency of the magnetite anode and its improvement in electrosynthesis efficiency. We will employ multiple spectroscopic techniques to probe the crystalline structural change of the magnetite minerals during its functioning as an anode material. Eventually, we will implement a four-electrode single-chamber bioelectrochemical system to complete an in-situ regeneration of the magnetite anode for its application in a commercially profitable large-scale system. The mechanistic understanding of how a magnetite anode functions is essential for achieving a high-performance microbial electrosynthesis.
DFG Programme
Priority Programmes
