RESUMEN
A selective composite membrane for vanadium redox flow battery (VRFB) was successfully prepared by layer-by-layer (LbL) technique using a perfluorosulfonic sulfonic acid or Nafion 117 (N117). The composite membrane referred as N117-(PEI/GO)n, was obtained by depositing alternating layers of positively charged polyethylenimine (PEI) and negatively charged graphene oxide (GO) as polyelectrolytes. The physicochemical properties and performance of the pristine and composite membranes were investigated. The membrane showed an enhancement in proton conductivity and simultaneously exhibited a notable 90% reduction in vanadium permeability. This, in turn, results in a well-balanced ratio of proton conductivity to vanadium permeability, leading to high selectivity. The highest selectivity of the LbL membranes was found to be 19.2 × 104 S.min/cm3, which is 13 times higher than the N117 membrane (n = 0). This was translated into an improvement in the battery performance, with the n = 1 membrane showing a 4-6% improvement in coulombic efficiency and a 7-15% improvement in voltage efficiency at current densities ranging from 40 to 80 mA/cm2. Furthermore, the membrane displays stable operation over a long-term stability at around 88% at a current density of 40 mA/cm2, making it an attractive option for VRFB applications using the LbL technique. The use of PEI/GO bilayers maintains high proton conductivity and VE of the battery, opening up possibilities for further optimization and improvement of VRFBs.
An innovative N117-(PEI/GO)n layer-by-layer membrane prepared for vanadium redox flow battery improved the balance between the proton conductivity and vanadium permeability, yielding a remarkable selectivity of 19.2 × 104 S.min/cm3.
RESUMEN
The scarcity of water leads to research nowadays to focus on techniques for treating wastewater. Photocatalysis emerged as a technique of interest due to its nature of friendliness. It utilizes light and catalyst to degrade the pollutants. One of the popular catalysts to be used is zinc oxide (ZnO), but its usage is limited due to the high recombination rate of electron-hole pair. Herein, in this study, ZnO is modified with graphitic carbon nitride (GCN), and the GCN loading amount was varied to study the impact on photocatalytic degradation of mixed dye solution. To the best of our knowledge, this is the first work that reports on the degradation of mixed dye solution using modified ZnO with GCN. Structural analysis showed that GCN is present in the composites which proves the success of the modification. Photocatalytic activity revealed that the composite with 5 wt% loading of GCN showed the best activity at a catalyst dosage of 1 g/L with degradation rates of 0.0285, 0.0365, 0.0869, and 0.1758 min-1 for methyl red, methyl orange, rhodamine B, and methylene blue dyes, respectively. This observation is expected due to the formation of heterojunction between ZnO and GCN which creates a synergistic effect and thus led to an improvement in the photocatalytic activity. Based on these results, ZnO modified with GCN has a good potential to be used in the treatment of textile wastewater which consists of various dye mixtures.
