Ferroelectric solid solution Li1 − xTa1 − xWxO3 as potential photocatalysts in microbial fuel cells: Effect of the W content

Abstract Microbial fuel cells (MFCs) are bio-electrochemical systems that can directly convert the chemical energy contained in an effluent into bioelectricity by the action of microorganisms. The performance of these devices is heavily impacted by the choice of the material that forms the cathode. This work focuses on the assessment of ferroelectric and photocatalytic materials as a new class of non-precious catalysts for MFC cathode construction. A series of cathodes based on mixed oxide solid solution of LiTaO 3 with WO 3 formulated as Li 1 −  x Ta 1 −  x W x O 3 ( x  = 0, 0.10, 0.20 and 0.25), were prepared and investigated in MFCs. The catalyst phases were synthesized, identified and characterized by DRX, PSD, MET and UV–Vis absorption spectroscopy. The cathodes were tested as photoelectrocatalysts in the presence and in the absence of visible light in devices fed with industrial wastewater. The results revealed that the catalytic activity of the cathodes strongly depends on the ratio of substitution of W 6 + in the LiTaO 3 matrix. The maximum power densities generated by the MFC working with this series of cathodes increased from 60.45 mW·m − 3 for x  = 0.00 (LiTaO 3 ) to 107.2 mW·m − 3 for x  = 0.10, showing that insertion of W 6 + in the tantalate matrix can improve the photocatalytic activity of this material. Moreover, MFCs operating under optimal conditions were capable of reducing the load of chemical oxygen demand by 79% (COD initial  = 1030 mg·L − 1 ).