Electric field induced alignment of graphene oxide nanoplatelets in polyethersulfone matrix

In recent years, in order to obtain improved mechanical, thermal, electrical and barrier/transport properties, aligned carbonaceous nanomaterials/polymer nanocomposite films have been receiving growing attention. Correspondingly, graphene oxide (GO) nanoplatelets alignment influence on the structure of the polyethersulfone (PES) membrane films for potential applications in water treatment field has been investigated. Aligned GO/PES nanocomposite membrane films were prepared by non-solvent phase inversion technique after the starting sol phase was preliminarily exposed to high electric fields (50 kV/m). Either AC (100, 1000 Hz) or DC mode electric fields were alternatively employed, and the results from both vertical and horizontal field configurations were investigated for structural and morphological comparison. Both XRD, FTIR-ATR, EIS, SEM, TEM and tensile strength analyses were applied in order to characterize the films. The microscopic analyses results have demonstrated successful GO/PES nanocomposite formation and alignment of GO nanoplatelets with the field direction in the matrix at low to moderate (0.02 to 0.1 %. wt) GO loadings where the flakes were dispersed and exfoliated sufficiently. However, at higher loading levels (1 and 2%. wt) the nanoplateles were mostly agglomerated and the big flakes consisting irregular plates could not orient their axis parallel to the electric field at the employed field strengths. The results suggest more effective role of higher frequencies (1000 Hz vs 100 Hz) electric field for alignment of GO nanoplatelets. Simple tensile tests have also similarly confirmed GO alignment under the electric fields at both low (0.1. % wt) and moderately high (0.5%. wt) GO contents. The tensile strength improvement of the horizontal field processed PES/GO nanocomposite up to 24% compared to its vertical field processed counterpart could be accounted as a proof of the successful alignment of the nanoplatelets. However, EIS results unveiled that non-solvent phase inversion casting method, in its general form, may not be a suitable method for producing materials with tailored properties, due to its random and uncontrollable pore forming mechanism

Advances in Carbon Nitride-Based Materials and Their Electrocatalytic Applications

As a group of large-surface-area nonmetal materials, polymeric carbon nitride (CxNy) and its hybrid structures are nowadays of ever-increasing interest for use in energy devices involved in energy conversion and storage, offering low expenses and facile production processes. With the growing requirement for clean and renewable energy generation and storage systems, progress in the replacement of expensive noble-metal catalysts with CxNy-based materials as efficient electrocatalysts has expanded considerably, and the demand for these materials has increased. The modified CxNy architectures are beneficial to electrocatalytic applications, improving their moderate electrical conductivities and capacity loss. The present review strives to highlight the recent advances in the research on the aforementioned identities of CxNy-derived materials and their structurally modified polymorphs. This review also discusses the use of CxNy-based materials in fuel cells, metal-air batteries, water splitting cells, and supercapacitor applications. Herein, we deal with electrocatalytic oxidation and reduction reactions such as hydrogen evolution, oxygen evolution, oxygen reduction, CO2 reduction, nitrogen reduction, etc. Each device has been studied for a clearer understanding of the patent applications, and the relevant experiments are reviewed separately. Additionally, the role of CxNy-derived materials in some general redox reactions capable of being exploited in any of the relevant devices is included