Abstract
During microbial electrosynthesis (MES) driven CO2 reduction, cathode plays a vital role by donating electrons to microbe. Here, we exploited the advantage of reduced graphene oxide (RGO) paper as novel cathode material to enhance electron transfer between the cathode and microbe, which in turn facilitated CO2 reduction. The acetate production rate of Sporomusa ovata-driven MES reactors was 168.5 ± 22.4 mmol m−2 d−1 with RGO paper cathodes poised at −690 mV versus standard hydrogen electrode. This rate was approximately 8 fold faster than for carbon paper electrodes of the same dimension. The current density with RGO paper cathodes of 2580 ± 540 mA m−2 was increased 7 fold compared to carbon paper cathodes. This also corresponded to a better cathodic current response on their cyclic voltammetric curves. The coulombic efficiency for the electrons conversion into acetate was 90.7 ± 9.3% with RGO paper cathodes and 83.8 ± 4.2% with carbon paper cathodes, respectively. Furthermore, more intensive cell attachment was observed on RGO paper electrodes than on carbon paper electrodes with confocal laser scanning microscopy and scanning electron microscopy. These results highlight the potential of RGO paper as a promising cathode for MES from CO2.
Highlights
Thin paper made of reduced graphene oxide (RGO) has a wide range of potential applications in research fields such as materials science, life sciences, environmental engineering, and electrochemical technologies[1,2,3,4,5,6]
We have investigated the biofilm formation on both RGO and carbon paper electrodes and their electrochemical behavior in detail
The intensity of all peaks corresponding to carbon-oxygen groups, especially the C-O-C peak, decreased significantly for RGO paper, revealing that most oxygen-containing functional groups were removed during the reduction reaction
Summary
Thin paper made of reduced graphene oxide (RGO) has a wide range of potential applications in research fields such as materials science, life sciences, environmental engineering, and electrochemical technologies[1,2,3,4,5,6]. Carbon paper is another paper-like material employed in electrochemical devices that share several properties with RGO papers such as high electrical conductivity, large surface area, biocompatibility, and low cost[11]. Carbon paper has been used extensively in the field of bioelectrochemistry to fabricate electrodes for the bioelectrochemical generation of electrical energy via microbial fuel cells[13,14,15,16]. Microbial electrosynthesis (MES) is a promising bioelectrochemical application in which the greenhouse gas CO2 is reduced into multicarbon products or methane with electrons derived from the cathode of an electrochemical reactor[20,21,22,23]. To construct an efficient cathode, the ideal material should possess good biocompatibility, high surface area, high durability, low production cost and high electrical conductivity[44]. We have investigated the biofilm formation on both RGO and carbon paper electrodes and their electrochemical behavior in detail
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