Ameliorating Cu²⁺ reduction in microbial fuel cell with Z-scheme BiFeO₃ decorated on flower-like ZnO composite...

BiFeO₃ nanoparticle decorated on flower-like ZnO (BiFeO₃/ZnO) was fabricated through a facile hydrothermal-reflux combined method. This material was utilized as a composite photocathode for the first time in microbial fuel cell (MFC) to reduce the copper ion (Cu²⁺) and power generation concomitantly. The resultant BiFeO₃/ZnO-based MFC displayed distinct photoelectrocatalytic activities when different weight percentages (wt%) BiFeO₃ were used. The 3 wt% BiFeO₃/ZnO MFC achieved the maximum power density of 1.301 W m^-2 in the catholyte contained 200 mg L^-1 of Cu²⁺ and the power density was greatly higher than those pure ZnO and pure BiFeO₃ photocathodes. Meanwhile, the MFC exhibited 90.7% removal of Cu²⁺ within 6 h under sunlight exposure at catholyte pH 4. The addition of BiFeO₃ nanoparticles not only manifested outstanding capability in harvesting visible light, but also facilitated the formation of Z-scheme BiFeO₃/ZnO heterojunction structure to induce the charge carrier transfer along with enhanced redox abilities for the cathodic reduction. The pronounced electrical output and Cu²⁺ reduction efficiencies can be realized through the synergistic cooperation between the bioanode and BiFeO₃/ZnO photocathode in the MFC. Furthermore, the developed BiFeO₃/ZnO composite presented a good stability and reusability of photoelectrocatalytic activity up to five cyclic runs.