Carbon nanotubes/polythiophene composite anodes: Fabrication and electrochemical energy storage performance

This study presents a significant advancement in a capacitive carbon felt/carbon nanotube/polythiophene (CF/CNT/PTh) bioanode. The CF framework provides mechanical stability. CNTs form a mesoporous structure (Barrett-Joyner-Halenda (BJH) pore volume: 0.016991 cm³/g), which supports increased populations of electroactive microorganisms. High-throughput sequencing confirmed a 6.67-fold increase in the relative abundance of electroactive genera. The key innovation of the CF/CNT/PTh is the incorporation of PTh to redesign the bioelectrochemical interface. The hydrophobic surface of PTh (confirmed by Fourier-transform infrared spectroscopy and Brunauer-Emmett-Teller analysis) reduces interfacial water barriers. Consequently, the charge-transfer resistance decreases by 65.3 % (R_ct = 2.80 Ω), as measured via electrochemical impedance spectroscopy. Additionally, the pseudocapacitive properties of PTh enable the storage of 5842.55C/m² of charge and generate a stronger bioelectric field (-578 mV open-circuit potential (OCP)), which enhances microbial activity. These effects create an "energy hub" in the bioanode, as stored and real-time electrons merge during discharge. Therefore, the CF/CNT/PTh bioanode achieves a current density of 147.925 A/m² and a power density of 1216.03 mW/m², which is 1.64 times that of bare CF. This design establishes a novel system through a microbial habitat environment constructed with CNT and a polythiophene-enhanced electron transfer mechanism, offering an innovative solution for micropower applications.