Graphene oxide

A comprehensive comparison between Bi$_{25}$FeO$_{40}$-reduced graphene oxide(rGO) nanocomposite and BiFeO$_{3}$-rGO nanocomposite has been performed to investigate their photocatalytic abilities in degradation of Rhodamine B dye and generation of hydrogen by water-splitting. The hydrothermal technique adapted for synthesis of the nanocomposites provides a versatile temperature-controlled phase selection between perovskite BiFeO$_{3}$ and sillenite Bi$_{25}$FeO$_{40}$. Both perovskite and sillenite structured nanocomposites are stable and exhibit considerably higher photocatalytic ability over pure BiFeO$_{3}$ nanoparticles and commercially available Degussa P25 titania. Notably, Bi$_{25}$FeO$_{40}$- rGO nanocomposite has demonstrated superior photocatalytic ability and stability under visible light irradiation than that of BiFeO$_{3}$-rGO nanocomposite. The possible mechanism behind the superior photocatalytic performance of Bi$_{25}$FeO$_{40}$-rGO nanocomposite has been critically discussed.

Published in: "arXiv Material Science".

Water dissociation is of fundamental importance in scientific fields and has drawn considerable interest in diverse technological applications. However, the high activation barrier of breaking the O-H bond within the water molecule has been identified as the bottleneck, even for the water adsorbed on the graphene oxide (GO). Herein, using the density functional theory calculations, we demonstrate that the water molecule can be spontaneously dissociated on GO supported by the (111) surface of the copper substrate (Copper-GO). This process involves a proton transferring from water to the interfacial oxygen group, and a hydroxide covalently bonding to GO. Compared to that on GO, the water dissociation barrier on Copper-GO is significantly decreased to be less than or comparable to thermal fluctuations. This is ascribed to the orbital-hybridizing interaction between copper substrate and GO, which enhances the reaction activity of interfacial oxygen groups along the basal plane of GO for water dissociation. Our work provides a novel strategy to access water dissociation via the substrate-enhanced reaction activity of interfacial oxygen groups on GO and indicates that the substrate can serve as an essential key to tune the catalytic performance of various two-dimensional material devices.

Published in: "arXiv Material Science".

Graphene sponge electrodes were employed for chlorine-free inactivation of Escherichia coli from low conductivity water. The nitrogen-doped reduced graphene oxide (NRGO) sponge anode bearing more positive charge achieved complete E. coli inactivation (i.e., 5 log removal) in the anode-cathode configuration at 115 A m-2, versus 2.6 log removal using boron-doped reduced graphene oxide sponge anode. The bacteria were mainly inactivated via electrosorption and electroporation, as confirmed by the scanning electron microscopy. Storage of the electrochemically treated samples revealed further killing of the bacteria due to the damaged cell membranes. When using real tap water, 5.5 log E. coli removal required 5.70 kWh m-3, which was drastically lowered to 1.38 kWh m-3 using intermittent current and thus exploiting the capacitive properties of graphene. The developed graphene sponge anode does not form any chlorine, chlorate, or perchlorate, and holds great promise for efficient electro-disinfection without forming toxic disinfection byproducts.

Published in: "arXiv Material Science".