Wool roving textured reduced graphene oxide-HoVO4-ZnO nanocomposite for photocatalytic and supercapacitor performance

Ultrasonic-assisted synthesis of CaCu3Ti4O12/reduced graphene oxide composites for enhanced photocatalytic degradation of pharmaceutical products: Ibuprofen and Ciprofloxacin

The objective of this research is to create a highly effective approach for eliminating pollutants from the environment through the process of photocatalytic degradation. The study centers around the production of composites consisting of CaCu3Ti4O12 (CCTO) and reduced graphene oxide (rGO) using an ultrasonic-assisted method, with a focus on their capacity to degrade ibuprofen (IBF) and ciprofloxacin (CIP) via photodegradation. The impact of rGO on the structure, morphology, and optical properties of CCTO was inspected using XRD, FTIR, Raman, FESEM, XPS, BET, and UV-Vis. Morphology characterization showed that rGO particles were dispersed within the CCTO matrix without any specific chemical interaction between CCTO and C in the rGO. The BET analysis revealed that with increasing the amount of rGO in the composite, the specific surface area significantly increased compared to the CCTO standalone. Besides, increasing rGO resulted in a reduction in the optical bandgap energy to around 2.09 eV, makes it highly promising photocatalyst for environmental applications. The photodegradation of IBF and CIP was monitored using visible light irradiation. The results revealed that both components were degraded above 97% after 60 min. The photocatalyst showed an excellent reusability performance with a slight decrease after five runs to 93% photodegradation efficiency.

Graphene-based strontium niobate-zinc oxide heterojunction photocatalyst for effective reduction of hexavalent chromium

A hydrothermal technique was employed to synthesize a Sr₂Nb₂O₇-rGO-ZnO (SNRZ) ternary nanocatalyst, in which ZnO and Sr₂Nb₂O₇ were deposited on reduced graphene oxide (rGO) sheets. The surface morphologies, optical properties, and chemical states, of the photocatalysts were characterized to understand their properties. The SNRZ ternary photocatalyst was superior over the reduction of Cr (VI) to harmless Cr (III) compared to the efficiencies obtained using bare, binary, and composite catalysts. The effects of various parameters, including the solution pH and weight ratio, on the photocatalytic reduction of Cr (VI) were investigated. The highest photocatalytic reduction performance (97.6%) was achieved at pH 4 and a reaction time of 70 min. Photoluminescence emission measurements were used to confirm efficient charge migration and separation across the SNRZ, which improved the reduction of Cr (VI). A feasible reduction mechanism for the SNRZ photocatalyst is proposed. This study presents an effective, inexpensive, non-toxic, and stable catalyst, for the reduction of Cr (VI) to Cr (III) using SNRZ ternary nanocatalysts.

Remediation of pharmaceutical pollutants using graphene-based materials - A review on operating conditions, mechanism and toxicology

Graphene is a high surface area special carbon compound with exceptional biological, electronic and mechanical properties. Graphene-based materials are potential components used in water treatment on different modes and processes. Ibuprofen and ciprofloxacin are two commonly found pharmaceutical contaminants discharged into water bodies from industrial, domestic and hospital sources. Their concentration levels in water bodies are reported in the range of 1 μg/L to 6.5 mg/L and 0.050-100 μg/L respectively. Their toxic effects pose very high risk to the inhabiting organisms. Their ability to resist biodegradation and capacity to bioaccumulate makes the conventional methods less effective in removal. In the present article, treatment of these compounds via three methods, adsorption, photocatalytic degradation and electro-fenton reactions using graphene-based materials along with the methods adopted for synthesis and treatment are reviewed. The uptakes obtained by graphene-derived adsorbents are presented along with the optimal operating conditions. Studies reported complete removal of ibuprofen from wastewater was achieved at 7 pH for 60 min using graphene membrane as adsorbent and uptake of 99% of ciprofloxacin was exhibited for graphene nanoplates/boron nitrate aerogel at a pH of 7 and 60 min. The reduced graphene oxide surface exhibits higher affinity to light adsorption which leads to the formation of photo generated electrons. The future perspectives for improved applications of graphene-based materials and the research gap currently existing are highlighted.

Rare Earth-Based Nanomaterials for Supercapacitors: Preparation, Structure Engineering and Application

Supercapacitors (SCs) can effectively alleviate problems such as energy shortage and serious greenhouse effect. The properties of electrode materials directly affect the performance of SCs. Rare earth (RE) is known as "modern industrial vitamins", and their functional materials have been listed as key strategic materials. In the past few years, the number of scientific reports on RE-based nanomaterials for SCs has increased rapidly, confirming that adding RE elements or compounds to the host electrode materials with various nanostructured morphologies can greatly enhance their electrochemical performance. Although RE-based nanomaterials have made rapid progress in SCs, there are very few works providing a comprehensive survey of this field. In view of this, a comprehensive overview of RE-based nanomaterials for SCs is provided here, including the preparation methods, nanostructure engineering, compounds, and composites, along with their capacitance performances. The structure-activity relationships are discussed and highlighted. Meanwhile, the future challenges and perspectives are also pointed out. This Review can not only provide guidance for the further development of SCs but also arouse great interest in RE-based nanomaterials in other research fields such as electrocatalysis, photovoltaic cells, and lithium batteries.

Facile synthesis of sphere-like structured ZnIn2S4-rGO-CuInS2 ternary heterojunction catalyst for efficient visible-active photocatalytic hydrogen evolution

Photocatalysis is a promising approach for generating hydrogen, an eco-friendly and cost-effective fuel. It is hypothesized that the ternary catalyst ZnIn₂S₄-rGO-CuInS₂, prepared by ultrasonication method, should be effective for optimized photocatalytic hydrogen generation in a Na₂S/Na₂SO_3-water mixture. The as-synthesized catalyst was characterized using various surface analytical and optical techniques. Field-emission scanning electron microscopy and high-resolution transmission electron microscopy analyses revealed that marigold-like structured ZnIn₂S₄ and layer-structured CuInS₂ were dispersed on the reduced graphene oxide sheets. The ternary ZnIn₂S₄-rGO-CuInS₂ system showed enhanced photocatalytic H₂ production compared to pure ZnIn₂S₄, CuInS₂, ZnIn₂S₄-rGO, CuInS₂-rGO, and ZnIn₂S₄-CuInS₂ catalysts under visible light illumination. The fabricated ZnIn₂S₄-rGO-CuInS₂ catalyst afforded hydrogen generation of 2531 μmol/g after 5 h. The enhanced performance of the ZnIn₂S₄-rGO-CuInS₂ catalyst originates from the synergetic effect with rGO as the electron transfer medium, and is confirmed by photocurrent density and photoluminescence measurements that indicate reduced recombination between the excited electron and hole pairs, and fast electron transfer in the ternary composite. The excellent performance of the ZnIn₂S₄-rGO-CuInS₂ catalyst for up to three consecutive cycles was demonstrated in cyclic stability tests under visible-light illumination.

Toward the Development of Disposable Electrodes Based on Holmium Orthovanadate/f-Boron Nitride: Impacts and Electrochemical Performances of Emerging Inorganic Contaminants

Rare-earth metal orthovanadates have great technological relevance in the family of rare-earth compounds owing to their excellent physical and chemical properties. A significant number of studies have been carried out on this class of compounds to exploit their electrochemical properties in virtue of variable oxidation states. But holmium vanadate (HoV) and its morphology selective synthesis have not been considered, which can have potential applications similar to the rest of the family. In this work, we propose the synthesis of superior architectures of HoV with a functionalized boron nitride (f-BN) nanocomposite. The synergistic effect between HoV and f-BN can have a positive effect on the physical characteristics of the nanocomposite, which can be explored for its electrochemical capacity. Here, HoV incorporated with f-BN is explored for the electrochemical detection of Hg²⁺ ions, which is known for its toxicity-induced environmental health hazards. The structural and compositional revelation reveals higher conductivity and faster electron transfer in the composite, which facilitates a wide working range (0.02-53.8 and 64.73-295.4 μM), low limit of detection (5 nM), higher sensitivity (66.6 μA μM^-1 cm^-2), good selectivity over 10-fold higher concentration of other interfering compounds compared to Hg²⁺ ion concentration, and good cycles stability (30 segments) toward Hg²⁺ ion detection. This also envisages the morphology selective synthesis and utilization of other rare-earth metals, whose electrochemical capacities are unexplored.