W2N-MXene composite anode catalyst for efficient microbial fuel cells using domestic wastewater

Microbial fuel cells (MFCs) have enormous potential to treat wastewater and reduce the energy demands of wastewater treatment plants while generating electricity using active microorganisms as biocatalysts. However, the practical application of MFCs is limited by the low power density produced, mainly due to poor anode performance. A tungsten nitride (W2N)-MXene composite catalyst is introduced to modify the anode surface for use in microbial fuel cells during domestic wastewater treatment. The aim is to improve the wettability, electrical conductivity, electron transfer efficiency, and microorganism attachment capability of the anode and ultimately increase the overall performance of the microbial fuel cell to produce electricity during wastewater treatment. In detail, a hydrofluoric acid etching approach is used to synthesize the Ti3C2Tx MXene, the urea glass technique is used to prepare the W2N particles, and an adequate mixing and heat treatment approach is used to produce the W2N-Ti3C2Tx composite catalyst. The W2N-Ti3C2Tx composite on carbon cloth anode provides one of the best performances recorded for MXene in this type of fuel cells and using real domestic wastewater: with a 523 % increase in the power density (548 mW m-2), an 83 % decrease in the chemical oxygen demand (COD), and a 161 % increase in the electron transfer efficiency compared to those of the plain carbon cloth. We demonstrate that this outstanding performance is due to the improvements in hydrophilicity and microorganism attachment, particularly nanowires (or pili) which promote electron transfer. The present work offers an exciting avenue toward the process scale-up and optimization of single-chamber microbial fuel cells.