Modified stainless steel for high performance and stable anode in microbial fuel cells
Graphical abstract
A high performance and stable anode was prepared for microbial fuel cells by surface modification of stainless steel mesh including steps of acid etching, binder-free carbon black (CB) coating and the low-temperature heat treatment below 400 °C. The modified anode could deliver a stable and high current density of 1.91 mA cm−2.
Introduction
Microbial fuel cell (MFC) is a device that use bacteria to oxide organic matters and transfer the chemical energy to electrical power [1]. MFC is able to use waste organic matters as fuels to generate electricity, thus is a promising technology for simultaneous wastewater treatment and energy recovery. Though, a tremendous progresses in the development of MFC and its related technologies has been made in the past few years [2], [3], [4], the increase of the performance of MFC is still a major challenge. As one of dominant factors that affect the performance of MFC, the anode has been attracting special attention. The function of anode is to provide the space for bacteria propagation and collect the electrons released by the electroactive bacteria. The microbial bioelectrocatalytic activity of the anode is mainly determined by the numbers of bacteria grown in the anode and the rate of electron transfer between the bacteria and the anode.
Carbon or graphite is one of popularly used anode materials for MFC due to its good conductivity and biocompatibility, excellent microbial adhesion performance and chemical stability. [2], [5], [6] Various types of carbon materials have been used as anodes in MFCs [5], [7], such as bulk or particulate porous carbon, fibrous carbon and powdery carbon materials. However, the bulk carbon material shows comparatively low specific conductivity of 0.77 ∼ 1.25 × 105 S m−1, which is one order of magnitude lower than metal materials, e.g. stainless steel (1 × 106 S m−1). Moreover, bulk carbon or graphite is in low mechanical property and mechanically rigid and is difficult to get into specific shapes.
Stainless steel (SS) materials show a sufficiently high electric conductivity and good corrosion resistance, as well as are comparatively inexpensive and easy to process and connect, thus are well suitable for up-scaling. The direct use of SS as anode material in microbial bioelectrochemical system is so far relatively rare [8], most likely because the Cr component in the SS would inhibit the microbial activity [9], [10] and lead to a low microbial bioelectrocatalytic activity. Surface modification of SS electrodes, including flame-oxidization[11], flame-deposition[12], binder and binder-free nanocarbon coating [13], [14], [15], [16] were recently taken to produce a more biocompatible electrode surface with enhanced microbial bioelectrocatalytic activity. However, the oxidation and deposition modification of SSs at the high temperature was stable under the negative potential of −0.2 V (vs Ag/AgCl), but they would face the risk of corrosion under the MFC environmental (under positive potential, e.g. +0.2 V vs Ag/AgCl) [17]; the coating of nanocarbon using polymer binder usually resulted in a high internal resistance and would hinder the electron transfer from the bacteria to the SS surface[16]; the coating of nanocarbon without polymer binder onto SS would have a low interaction and resulted in unstable current generation[15].
In this paper, the microbial bioelectrocatalysis of stainless steel mesh (SSM) was greatly enhanced by a surface modification process including steps of acid etching, binder-free carbon black (CB) coating and low-temperature heat treatment. The modified SSM electrode could generate a high current density of up to 1.91 mA cm−2, is nearly three orders of magnitude higher than the untreated SSM electrode (0.0025 mA cm−2). Moreover, the modification layer was firm and corrosion-resistant, it still could deliver the equal current density after removing the formed biofilms.
Section snippets
Materials
304 stainless steel mesh (SSM) (Hongye Stainless Steel Wire Cloth Co.,Ltd, Hengshui, Hebei, containing about 19% Cr and 9% Ni) with mesh size of 50 and wire diameter of 0.20 mm, and carbon black (CB, VULCAN® XC72) were used as received.
Electrode preparation
The electrode preparation steps was illustrated in Scheme 1. SSM was washed by acetone to remove the impurity on the surface, then was immerged in 1 M H2SO4 solution and etched for different times under room temperature. The resulted SSM electrodes was named as SSM-
Bioelectrochemical activity of acid-etched SSM
It was well-known that the as-received commercial SSM was covered by a layer of compact passivation layer which mainly consisted of FeCr2O4, MnCr2O4 and FeOOH to prevent the SSM from rusting [20], [21]. After being etched by dilute H2SO4 solution, the passivation layer on the SSM surface was removed and a rough SSM surface was obtained, as shown in Fig. 1A and B. Moreover, SSMs with different etching ratio and different roughness were obtained after etching for different time, as shown in Table
Conclusion
The microbial bioelectrocatalysis of the SSM was greatly enhanced by a surface modification process including steps of acid etching, binder-free CB coating and heating treatment. The acid-etched SSM could increase the current density nearly two orders of magnitude due to the removal of the passivation layer and formation of rough surface. The SSM/CB prepared by binder-free coating CB onto the acid-etched SSM further boosted the current density one order of magnitude, from 0.161 to 1.85 mA cm−2
Acknowledgements
This research was supported by the National Natural Science Foundation of China (No. 51202096, No.21464008), the Science and Technology Project of Jiangxi Province (No. 20121BBE50024, 20143ACB21015).
References (24)
- et al.
Trends Biotechnol.
(2005) - et al.
J. Power Sources
(2011) - et al.
Bioresour. Technol.
(2011) - et al.
Bioresour. Technol.
(2011) - et al.
Electrochim. Acta
(2007) - et al.
J. Power Sources
(2011) - et al.
J. Power Sources
(2013) - et al.
Bioresour. Technol.
(2013) - et al.
J. Power Sources
(2015) - et al.
J. Power Sources
(2014)
Electrochim. Acta
Biosens. Bioelectron.
Cited by (42)
Advancements on sustainable microbial fuel cells and their future prospects: A review
2022, Environmental ResearchCitation Excerpt :Some studies have been conducted to modify pristine metal and carbon-based anodes to enhance their electron transfer rate. The bare anode is subjected to heat or chemical (acid and ammonia) treatment (Peng et al., 2016; Abbas et al., 2021) and electrochemical oxidation (Zhou et al., 2012, Umapathi et al., 2021; Umapathi et al., 2022). Such treatments afford three-dimensional structures that alter the surface and enlarge the active surface area of the anode.
Metal-organic framework-derived iron oxide modified carbon cloth as a high-power density microbial fuel cell anode
2022, Journal of Cleaner ProductionAnode modification: An approach to improve power generation in microbial fuel cells (MFCs)
2022, Development in Wastewater Treatment Research and Processes: Bioelectrochemical Systems for Wastewater ManagementMicro/nanostructures for biofilm establishment in microbial fuel cells
2022, Nanotechnology in Fuel CellsNanostructures and nanomaterials in microbial fuel cells
2022, Nanotechnology in Fuel Cells