In the water sector, there are many challenges to overcome. For example, the industry needs more efficient and affordable wastewater or process treatment. To achieve these goals, innovative materials are needed that can improve existing processes and introduce new ones. Carbon-based electrodes, for example, are capable of offering high current densities and corrosion resistance. It is also simple to scale-up and fabricate. Their characteristics allow them to be used in a range of applications.
This study investigated the performance and characteristics of graphite electrodes in EAOP. Comparing borondoped-diamond (BDD) and RVC in a two-electron-oxygen-reduction electrochemical reactor. The porous GF and RVC outperformed non-porous BDD at lower potentias with greater limiting currents. The results indicate that the superior pore structure and surface roughness of GF and rVC, together with their high conductivity, are key factors in their excellent performance in EAOP.
GF was subjected to a variety of surface treatments in order to improve the EAOP electrode properties. The microbial bioanode current production was determined using chronoamperometry and it was found that the average current densities of the bioanodes generated on the treated graphite surfaces were higher by 17% to 56% compared to that on the control. The microbial community composition was studied by metagenomics pyrosequencing, which showed that bacteria belonging to the family of Geobacteraceae were predominant in the biofilms grown on the treated graphite surfaces (A + E and A) whereas they were not dominant in the biofilms formed on the control electrodes.
In SEM pictures of the treated bioanode surfaces, the surface had a smoother appearance with lower pore volumes and reduced roughness. Sku, a measure of sharpness of the graphite surfaces modified with acid and electrochemical surface treatments showed remarkably improved values. XPS tests confirmed that the improved surface chemistry was present on the graphite modified surface (Table 3).
In addition to their high electrical conductivity, porous GF and rVC have a large specific surface area and a low density. It is crucial for mass transportation, which leads to improved H2O and oxygen production, as well as electrochemical efficiency. In fact, the bioanode-current production by GF and the rVC is much higher than for the BDD nonporous cathode. In addition, GF/rVC's excellent mechanical strength and chemical resistance made it suitable for repeat use in tough conditions. Additionally, they are low-vapor pressure materials and can tolerate up to 350degC. These results indicate that GF/rVC is a promising candidate for electrodes in the EAOPs to produce H2O efficiently. This study is a major step forward in achieving environmentally and economically friendly water-treatment technologies.
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