Invited feature articleA biocathode-driven photocatalytic fuel cell using an Ag-doped TiO2/Ti mesh photoanode for electricity generation and pollutant degradation

•A well-prepared Ag-doped TiO2/Ti 3D nanotube arrays formed on Ti mesh.•High efficiency in the degradation of pollutant compared to TiO2/Ti electrode.•Biocathode-driven PFC system for electricity generation.•Electrotrophic microorganisms are determined in biocathode.

A biocathode-drived photocatalytic fuel cell (bio-PFC) was established for simultaneous refractory wastewater treatment and electricity generation. The successful doping of Ag nanoparticles into the three-dimensional arrays of TiO2 nanotubes formed on Ti mesh was found to effectively reduce recombination of the photogenerated carriers and extend the light absorption properties of TiO2. The biocathode provided the sustainable oxygen-reducing reaction in cathode, which eliminated the persistent kinetic limitations using abiotic cathode and ensured the stable operation of photoanode. The bio-PFC using Ag/TiO2 photoanode achieved higher RhB degradation efficiency of 99.5% with the k of 0.0451 min−1, compared to that using TiO2 photoanode (degradation efficiency of 97.3% with the k of 0.0301 min−1). A maximum power density of 318.19 mW m−2 at a current density of 1.26 mA m−2 was obtained. Pyrosequencing revealed that the cathodic microbial community was dominated by electrographic microorganisms including Acinetobacter sp., Shewanella sp., and nitrifiers (Nitrospira sp., Nitrobacter sp., Nitrosococcus sp.). Little differences in cathodic microbial structures were observed between the bio-PFCs using Ag/TiO2 and TiO2 photoanodes, indicating the improvement of system performance was mainly attributed to the effective modification of TiO2 by Ag doping.

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