Oxic microbial electrosynthesis using aerobic hydrogenotrophic bacteria requires productive cathodic biofilm formation, yet reactive oxygen species generated at the electrode surface present a critical barrier to initial colonisation. In this study, the authors investigate biofilm development by Cupriavidus necator H16 on Aerographite, an ultralow-density carbon foam with a hierarchical tetrapodal pore network and a porosity above 99 percent, used as a cathode material in microfluidic bioelectrochemical systems. Its performance is compared with graphite, a composite material consisting of graphite and polypropylene.
A biphasic cultivation strategy, in which heterotrophic biofilm establishment preceded a switch to electroautotrophic conditions, successfully overcame the reactive oxygen species barrier on both electrode materials. Noninvasive optical coherence tomography revealed a final biovolume on graphite after 14 days, representing the first continuous kinetic characterisation of C. necator cathode biofilm formation under defined flow conditions. Despite a lower absolute biovolume per projected area, Aerographite supported higher biomass per unit electrode mass, reflecting its 585-fold higher mass-specific electroactive surface area relative to graphite.
Scanning electron microscopy confirmed colonisation of internal pore regions up to 500 micrometres below the electrode surface under laminar flow-over conditions. The macropore dimensions substantially exceed documented self-limiting biofilm thicknesses, indicating that pore occlusion is unlikely even at full biofilm development. The results position Aerographite as a structurally enabling electrode material for smart, scalable, flow-through carbon dioxide valorisation systems.
The study is a collaboration between Hamburg University of Technology and Kiel University, carried out within the Collaborative Research Centre CRC 1615 (SMART Reactors).
Sri Sannihita Chavali, Christiane Roller, Tom Liebing, Jonas Lumma, Morten Möller, Rainer Adelung, Thorsten Alexander Kern, Miriam Edel, Bodo Fiedler, Johannes Gescher (2026). Aerographite vs Graphite: Investigating the Role of Electrode Architecture in H2-Mediated Electroautotrophic Biofilms. Ind. Eng. Chem. Res. 65 (32), 17018-17029.
