Influence of carbon-based cathodes on biofilm composition and electrochemical performance in soil microbial fuel cells

Increasing energy demands and environmental pollution concerns press for sustainable and environmentally friendly technologies.Soil microbial fuel cell(SMFC)technology has great potential for carbon-neutral bioenergy generation and self-powered electrochemical bioremediation.In this study,an in-depth assessment on the effect of several carbon-based cathode materials on the electrochemical performance of SMFCs is provided for the first time.An innovative carbon nanofibers electrode doped with Fe(CNFFe)is used as cathode material in membrane-less SMFCs,and the performance of the resulting device is compared with SMFCs implementing either Pt-doped carbon cloth(PtC),carbon cloth,or graphite felt(GF)as the cathode.Electrochemical analyses are integrated with microbial analyses to assess the impact on both electrogenesis and microbial composition of the anodic and cathodic biofilm.The results show that CNFFe and PtC generate very stable performances,with a peak power density(with respect to the cathode geometric area)of 25.5 and 30.4 mW m^(−2),respectively.The best electrochemical performance was obtained with GF,with a peak power density of 87.3 mW m^(−2).Taxonomic profiling of the microbial communities revealed differences between anodic and cathodic communities.The anodes were predominantly enriched with Geobacter and Pseudomonas species,while cathodic communities were dominated by hydrogen-producing and hydrogenotrophic bacteria,indicating H_(2)cycling as a possible electron transfer mechanism.The presence of nitrate-reducing bacteria,combined with the results of cyclic voltammograms,suggests microbial nitrate reduction occurred on GF cathodes.The results of this study can contribute to the development of effective SMFC design strategies for field implementation.

Recent Advances in the Unconventional Design of Electrochemical Energy Storage and Conversion Devices

As the world works to move away from traditional energy sources,effective efficient energy storage devices have become a key factor for success.The emergence of unconventional electrochemical energy storage devices,including hybrid batteries,hybrid redox flow cells and bacterial batteries,is part of the solution.These alternative electrochemical cell configurations provide materials and operating condition flexibility while offering high-energy conversion efficiency and modularity of design-to-design devices.The power of these diverse devices ranges from a few milliwatts to several megawatts.Manufactur-ing durable electronic and point-of-care devices is possible due to the development of all-solid-state batteries with efficient electrodes for long cycling and high energy density.New batteries made of earth-abundant metal ions are approaching the capacity of lithium-ion batteries.Costs are being reduced with the advent of flow batteries with engineered redox molecules for high energy density and membrane-free power generating electrochemical cells,which utilize liquid dynamics and interfaces(solid,liquid,and gaseous)for electrolyte separation.These batteries support electrode regeneration strategies for chemical and bio-batteries reducing battery energy costs.Other batteries have different benefits,e.g.,carbon-neutral Li-CO_(2) batteries consume CO_(2) and generate power,offering dual-purpose energy storage and carbon sequestration.This work considers the recent technological advances of energy storage devices.Their transition from conventional to unconventional battery designs is examined to identify operational flexibilities,overall energy storage/conversion efficiency and application compatibility.Finally,a list of facilities for large-scale deployment of major electrochemical energy storage routes is provided.