In this study we show that a chemical ferricyanide cathode can be replaced by a biological oxygen reducing
cathode in a plant microbial fuel cell (PMFC) with a new record power output. A biocathode was successfully
integrated in a PMFC and operated for 151 days. Plants growth continued and the power density
increased reaching a maximum power output of 679 mW/m2 plant growth area (PGA) in a 10 min polarization.
The two week record average power densities was 240 mW/m2 PGA. The new records were
reached due to the high redox potential of oxygen reduction which was effectively catalyzed by microorganisms
in the cathode. This resulted in a 127 mV higher cathode potential of the PMFC with a biocathode
than a PMFC with a ferricyanide cathode. We also found that substrate availability in the anode likely
limits the current generation. This work is crucial for PMFC application as it shows that PMFC can be a
completely sustainable biotechnology with an improved power output.