Rational Selection of Carbon Fiber Properties for High-Performance Textile Electrodes in Bioelectrochemical Systems

Abstract

Novel applications of bioelectrochemical systems (BES) are emerging constantly, but the majority still lacks economic viability. Especially the use of electrochemical system components without adaptation to BES requirements causes poor exploitation of the potential system performance. The electrode material is one central component that determines BES performance. While commercial carbon fiber (CF) fabrics are commonly used, their customizability as two-or three-dimensional electrode material for BES is rarely investigated. Using pure cultures of S. oneidensis MR-1, we identified CF properties impacting bacterial current generation: (1) The removal of the sizing (protective coating) is of great importance for all the fibers studied, as it acts as an electrical insulator. By desizing, the maximum current density (j max) is increased by up to 40-fold. (2) Alteration of the filament surface chemistry results in an accelerated initial development of current generation, but the maximum current density (j max) is hardly affected. (3) A specific yarn structure, the stretch-broken yarn, supports exceptionally high current densities. The good electrode performance is correlated to the presence of free filament ends (responsible for 41% current increase), which are characteristic for this yarn. (4) Moreover, a combination of these free filament ends with a high degree of graphitization enhances electrode performance of a commercial fabric by 100%. The results demonstrate that the CF selection can greatly influence the achievable electrode performance of CF fabrics, and thereby contributes to rational engineering of CF based electrodes that can be tailored for the many BES applications envisaged.

High current production ofShewanella oneidensiswith electrospun carbon nanofiber anodes is directly linked to biofilm formation

“…1A, red), a maximum current density of (255±71) µA cm −2 was recorded with the ES300 material. This current density is about 1.4-fold higher than the highest value of 186 µA cm −2 reported up to now Pötschke et al [2019]. A trend towards higher current densities with decreasing fiber diameter is apparent (Fig.…”

“…Similar to our results, the increasing current production with decreasing fiber diameter could result from the macrostructure with a larger accessible surface area and smaller macropores. In a study by Pötschke et al [27], the effect of the chemical carbon fiber composition and fiber breaks on the current production was investigated. SEM images of fiber bundles depicted in Tab.…”

“…Increased current production was observed with increasing specific BET surface area. Pötschke et al [2019] investigated the carbon composition and fiber breaks. They identified a combination of highly conductive graphitic carbon, and free filament ends as key to high current densities.…”

“…Additionally, the electrospun carbon fiber surface was modified by steam and CO 2 activation to increase the surface area further and introduce micro-and mesopores, which have been hypothesized to enhance MET [Kipf et al, 2013, Patil et al, 2013]. We also reevaluate previous systematic anode material studies [Kipf et al, 2013, Patil et al, 2013, Pötschke et al, 2019] based on the premise that mainly the macrostructure of the anode determines the current production and biofilm formation of MR-1. The commercial reference materials were investigated previously [Dolch et al, 2014, Förster et al, 2017, Kipf et al, 2013, 2014] and serve as a benchmark in this work.…”

Microbial Electrolysis Cells for Decentralised Wastewater Treatment: The Next Steps

“…Carbon fibre (CF) electrodes are functional and have been showed to achieve high performances in previous studies [61]. However, they are more expensive [62]. Mesh CF anodes tend to produce higher current densities than plate shaped anodes due to better mass transfer, surface area and biofilm formation.…”