Three-dimensional hierarchical MoO2/MoC@NC-CC free-standing anode applied in microbial fuel cells

Abstract

In general, enrichment of a higher number of exoelectrogens implies higher power density. However, the low electrocatalytic activity of anodes limits the performance of microbial fuel cells. Here, based on this consideration, we designed and fabricated an anode by integrating the 3D hierarchical architecture and excellent electrocatalytic activity of MoO₂/MoC@NC nanodendrites grown on carbon fiber cloth. The as-designed MoO₂/MoC@NC-CC electrode exhibits a relatively large specific areal capacitance of 710.21 F m⁻² and a charge transfer resistance of only 5.29 Ω, which are 46.9 times higher and 67.9 times lower than those of the bare carbon cloth (CC) anode respectively, providing abundant electroactive sites for the colonization of exoelectrogens and accelerating the rate of extracellular electron transfer. At the same time, there was a positive correlation between the enrichment amount of Geobacter and the power density, demonstrating the successful preparation of the desired electrode. In addition, the branched-lily-like architecture of the MoO₂/MoC@NC-CC anode exhibits super hydrophilicity and open 3D structure, facilitating microbial attachment, colonization, proliferation and diffusion of the internal culture matrix, thus shortening the start-up time and improving the long-term stable current output. Consequently, the MoO₂/MoC@NC-CC anode achieved the maximum power density of 2.93 W m⁻², which is improved by 70.3% compared to that of the bare CC, and is also the best among the reported Mo-based nanomaterial modified electrodes. This work presents valuable insights for the design and fabrication of high performance anodes for MFCs.