A simple, green, novel, time-efficient, and potentially cost-effective water activation method was employed to enhance the electrochemical activity of graphite felt (GF) electrodes for vanadium redox ...flow batteries (VRFBs). The GF electrode prepared with a water vapor injection time of 5 min at 700 °C exhibits the highest electrochemical activity for the VO2+/VO2+ couple among all the tested electrodes. This is attributed to the small, controlled amount of water vapor that was introduced producing high contents of oxygen-containing functional groups, such as OH groups, on the surface of the GF fibers, which are known to be electrochemically active sites for vanadium redox reactions. Charge–discharge tests further confirm that only 5 min of GF water activation is required to improve the efficiency of the VRFB cell. The average coulombic efficiency, voltage efficiency, and energy efficiency are 95.06%, 87.42%, and 83.10%, respectively, at a current density of 50 mA cm-2. These voltage and energy efficiencies are determined to be considerably higher than those of VRFB cells assembled using heat-treated GF electrodes without water activation and pristine GF electrodes.
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•The effect of water activation on the electrochemical activity of GF is investigated.•A high content of oxygen-containing groups improves the performance of VRFB.•Improved wettability due to increased surface-active oxygen functional groups.•WA-GF-5 min improves battery energy efficiency from 69.84% to 78.12% at 80 mA cm-2.•WA-GF-5 min acts as more powerful positive electrode for the VO2+/VO2+ redox couple.
•Cu2O NWs@rGO/CuF with exposed {111} facet was fabricated by feasible electrodeposition route.•Cu2O NWs@rGO/CuF has a hydrophilic nanostructure and provides a certain degree of influence on the ...fouling level.•Cu2O NWs with exposed {111} facet could reduce ion diffusion distance and couple with improved electronic conductivity.•Cu2O NWs@rGO/CuF exhibits long-term stability for sensitive and efficient glucose detection in human blood.•Cu2O NWs {111} could adsorb and catalyze glucose oxidation in human blood effectively via DFT calculations.
Accurate glucose sensing in complex biological fluids could enable diagnostics for home healthcare. However, glucose oxidase (GOx) has been suffered from poor reproducibility and chemical instability due to intrinsic nature of enzymes. Here, we report a free-standing and robust reduced graphene oxide wrapped Cu foam (rGO/CuF)-supported Cu2O nanowires (Cu2O NWs) with exposed {111} facet via facile electrodeposition route. When being used as an electrode for nonenzymic glucose detection, Cu2O NWs@rGO/CuF exhibited the distinguished performances with powerful reliability for analyzing human plasma and even whole blood samples. These unprecedented performances could be ascribed to nanoscale hydrophilic structure of Cu2O NWs, which could control the fouling level especially for protein. Moreover, taking into account the Cu2O NWs with exposed {111} facet, Cu2O NWs {111} could reduce ion diffusion distance and couple with improved electronic conductivity, thus leading to high glucose sensitivity. Through the theoretical calculations, a reliable interpretation of the catalytic mechanism with Cu2O NWs {111} has been provided. This study deepens the understanding of hydrophilic nanostructure and facet-dependent activity of Cu2O NWs and points out a strategy to improve their sensitivity and stability.
Hierarchical porosity and the exposure of sufficient active sites are primary features for robust frameworks designed towards efficient adsorption, especially that of large molecules. Herein, we have ...introduced a powerful strategy called linker transformation to create mesopores and Cu2O nanoparticles in CuBTC simultaneously. Relying on this method, we constructed hierarchically porous CuBTC with tunable pore size distribution, and the crystallinity and stability were maintained after adding transformed linkers. Furthermore, linker transformation promoted the formation of Cu2O nanoparticles immobilized in the open framework of CuBTC, which exhibited more active sites for sulfur compounds. The hierarchical porous structure enabled easy diffusion of large-sized sulfur compounds, while the small Cu2O nanoparticles were highly dispersed, which led to highly enhanced desulfurization adsorption performance. The strategy presented here may provide new insights for designing more abundant MOF structures and further expanding their application range.
We report a catalyst-free pathway for the polymerization of furfuryl alcohol (FA) into poly(furfuryl alcohol) (PFA) using a deep eutectic solvent (DES) system. The DES prepared by mixing choline ...chloride (ChCl) and zinc chloride (ZnCl
2
) to polymerize FA in high yield under comparatively moderate reaction conditions. The FA conversion was found to increase with increasing reaction temperature and weight ratio of DES/FA. The highest yield of PFA (92.5%) was achieved at 80 °C in 4 h using a weight ratio of DES : FA of 10. FT-IR,
1
H and
13
C NMR, TGA, XRD and DSC analytical techniques were used to elucidate the structure and thermal behavior of the end product to confirm the successful formation of PFA. Moreover, we investigated the kinetics and calculated the activation energy for the reaction. A plausible mechanism for the reaction was proposed, focusing on the important role of the Ch
+
cation to initiate the polymerization process. The main advantage of this work is the exploitation of DES systems as a recyclable medium that can efficiently catalyze FA polymerization without using any external solvent and catalyst.
A catalyst-free pathway for the polymerization of furfuryl alcohol (FA) into poly(furfuryl alcohol) (PFA) using a deep eutectic solvent (DES) system is reported.
The photocatalytic process over semiconducting oxide surfaces has attracted worldwide attention as a potentially efficient, environmentally friendly, and low-cost method for wastewater treatment. ...This study presents a straightforward, inexpensive, and rapid route for the synthesis of nickel oxide (NiO) and its composites with zinc oxide (NiO/ZnO) and copper oxide (NiO/CuO) nanoparticles through the chemical precipitation method using capping agent-hexadecyltrimethylammonium bromide (CTAB) for photocatalytic degradation of the methylene blue dye. The structure, morphology, and elemental constituents were characterized by X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The energy band gap of pure NiO, NiO-ZnO, and NiO-CuO composites was evaluated using the Tauc plot from absorption spectra and resulted as 3.00, 2.90, and 3.25 eV, respectively. The optimum parameters for all photocatalysts were the following: pH 8, irradiation time 175 min, catalyst amount 75 mg, and dye concentration 7 mg/L. At these optimum parameters, the degradation efficiency of the prepared photocatalysts toward the MB dye achieved was 89.8% for NiO, 97% for NiO/ZnO, and 94.2% for NiO/CuO. The highest activity of the p-type/n-type (NiO/ZnO) nanocomposite for MB degradation is possibly due to electron–hole pair recombination inhibition by charge transfer processes. Therefore, semiconducting composite-based nanocatalysts such as NiO/ZnO with high photocatalytic activity are promising for future industrial applications to remove undesirable organic pollutants from the environment.
As one of the most promising electrochemical energy storage systems, vanadium redox flow batteries (VRFBs) have received increasing attention owing to their attractive features for large-scale ...storage applications. However, their high production cost and relatively low energy efficiency still limit their feasibility. One of the critical components of VRFBs that can significantly influence the effectiveness and final cost is the electrode. Therefore, the development of an ideal electrocatalyst with low cost, high electrical conductivity, large active surface area, good chemical stability, and excellent electrochemical reaction activity toward the VO
2+
/VO
2
+
and V
2+
/V
3+
redox reactions is essential for the design of VRFBs. Extensive research has been carried out on electrode modification routes for VRFBs to improve the energy density and overall performance for large-scale applications. This review article focuses on numerous state-of-the-art modification methods for VRFB electrodes, including those based on carbon materials, metal and metal oxide-based materials, and metal oxide/carbon composite materials. The challenges in the development of electrode materials and future research directions are also proposed.
This review article highlights the current research progress and future prospects of powerful electrode materials for Vanadium Redox Flow Battery (VRFB) applications.
Tetracyclines are extensively used to treat human and animal infectious diseases due to its effective antimicrobial activities. About 70–90% of its parent materials are released into the environment ...through urine and feces, implying they are the most frequently detected antibiotics in the environment with high ecological risks. Adsorption and photocatalysis have been promising techniques for the removal of tetracyclines due to effectiveness and efficiency. Graphene-based materials provide promising platforms for adsorptive and photocatalytic removal of tetracyclines from aqueous environment owning to distinctive remarkable physicochemical, optical, and electrical characteristics. Herein, we intensively reviewed the available literatures in order to provide comprehensive insight about the applications and mechanisms of graphene-based materials for removal of tetracyclines via adsorption and phototocatalysis. The synthesis methods of graphene-based materials, the tetracycline adsorption and photocatalytic-degradation conditions, and removal mechanisms have been extensively discussed. Finally concluding remarks and future perspectives have been deduced and recommended to stimulate further researches in the subject. The review study can be used as theoretical guideline for further researchers to improve the current approaches of material synthesis and application towards tetracyclines removal.
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•Extensive use of tetracyclines poses environmental pollution.•Adsorption and photocatalysis are excellent approaches to treat tetracyclines.•Graphene-based materials are promising platforms for TCs removal.•Surface modification of graphene exhibits excellent adsorptive performance.•Graphene sheets inhibit photo-induced electron/hole recombination during degradation.
In this paper, we propose a new, abundant, cost-effective, non-toxic, and environmentally benign iron–copper redox flow battery (Fe/Cu RFB), which employs Fe2+/Fe3+ and Cu+/Cu0 as the positive and ...negative electrolytes, respectively. The effect of graphite felt (GF) electrode modification and addition of Bi3+ into the electrolytes on the performance of the Fe/Cu RFB were investigated. It was found that the cell containing Bi3+ in the electrolytes revealed higher coulombic efficiency (89.18%) and energy efficiency (35.24%) than the cell without Bi3+ (CE = 84.10% and EE = 34.43%) at 20 mA cm−2. This is because after adding Bi3+, Cu metal precipitation was not observed on the electrode surface, which indicates that the deposition process was potentially reversible on the electrode material, thus leading to enhanced performance of the battery. Furthermore, the efficiencies of the battery are stable over 10 cycles, which demonstrates that Fe/Cu RFB exhibits good stability on the microwave heat treated GF plus one layer microwave heat treated carbon paper (HT-GF + HT-CP) electrode after adding Bi3+ into the electrolytes.
In this study, kocho was prepared from pseudostem and corm of Ensete ventricosum (enset).The behaviors of kocho were examined by using FESEM, TGA, XRD and FTIR spectroscopy. The biosorption potential ...of kocho, a possible low-cost new biosorbent for the efficient removal of MB dye from wastewater was investigated. Biosorption experiments were carried out in batch mode to study the effects of biosorbent dosages (0.025-0.2 g), pH (2–10), initial concentrations of MB (10 to 100 mg/L) and contact time (10 to 120 min).The highest removal efficiency of methylene blue dye (94.2%) was recorded at optimum experimental conditions. Following the removal study, it was determined that the pseudo-second order kinetics (R2 = 0.997) and Langmuir isothermal (R 2= 0.996) models may well describe the MB dye biosorption process. Furthermore, this newly developed biosorbent was fairly recyclable up to five cycles without significant loss of re-adsorption efficiency (around 9.6% loss) between 1st and 5th cycle. Thus, the findings of this study revealed that a new kocho biosorbent derived from Ensete ventricosum can be used as a promising low-cost, environmentally friendly and efficient biosorbent for the rapid removal of MB from aqueous solutions.
KEY WORDS: Kocho, Ensete ventricosum, Biosorption, Methylene blue, Kinetics, Isothermal
Bull. Chem. Soc. Ethiop. 2024, 38(1), 69-84. DOI: https://dx.doi.org/10.4314/bcse.v38i1.6
In this study, a simple, low-cost, and powerful titanium niobium oxide–reduced graphene oxide (TiNb2O7–rGO) nanocomposite electrocatalyst was synthesized through dispersion and blending in aqueous ...solution followed by freeze-drying and annealing for all-vanadium redox flow batteries (VRFBs). The TiNb2O7 nanoparticles are uniformly anchored between the rGO sheets; simultaneously, the rGO sheets are separated using TiNb2O7 nanoparticles. The synergistic effects between them prevent the agglomeration of the nanoparticles and restacking of the rGO sheets. The cyclic voltammetry and electrochemical impedance spectroscopy results reveal that among all the prepared samples, the TiNb2O7–rGO nanocomposite electrocatalyst exhibits the most favorable electrocatalytic activity toward VO2+/VO2+ and V3+/V2+ at the positive electrode and the negative electrode, respectively, to facilitate the electrochemical kinetics of the vanadium redox reactions. The corresponding energy efficiency is improved by ∼11.1% and 12.34% at current densities of 80 and 120 mA cm−2, respectively, compared with that of pristine graphite felt. The superior performance of the TiNb2O7–rGO nanocomposite electrode may have been due to the synergistic effects related to the high electronic conductivity of rGO nanosheets and the interfacial properties created within TiNb2O7 and rGO. Furthermore, the charge–discharge stability test demonstrates the outstanding stability of the TiNb2O7–rGO electrode. The TiNb2O7–rGO-based VRFB exhibits negligible activity decay after 200 cycles. The remarkable electrocatalytic activity and mechanical stability are achieved due to the TiNb2O7–rGO nanocomposite being strongly anchored on the graphite felt surface for a substantial time during repetitive cycling.
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