Ameliorating Cu reduction in microbial fuel cell with Z-scheme BiFeO decorated on flower-like ZnO composite photocathode.

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