2D-2D nanohybrids of Ni–Cr-layered double hydroxide and graphene oxide nanosheets: Electrode for hybrid asymmetric supercapacitors

Enhanced sonophotocatalytic degradation of phthalate acid ester using copper-chromium layered double hydroxides on carbon nanotubes and biochar

Layered double hydroxides (LDHs) are lamellar and stable nanocatalysts driven by visible light. They have received much attention in the context of advanced oxidation processes. Their catalytic performance is remarkably restricted owing to undesired aggregation and the possibility of electron-hole recombination. To address these issues, we engineered carbon-nanotube (CNT)-and biochar (BC)-based CuCr LDH nanocomposites via a facile hydrothermal method. The synthesized nanocomposites were physically and chemically characterized using various methods. The performances of the BC-CuCr LDH and CNT-CuCr LDH nanocomposites were compared during the sonophotocatalytic degradation of dimethyl phthalate. With 1.5 g L-1 of BC-CuCr LDH, complete degradation of dimethyl phthalate was achieved within 25 min under 50 W light intensity and 150 W ultrasound irradiation with a synergy factor of 14. The critical roles of the hydroxyl and superoxide radicals were confirmed by the addition of several inhibitors. Ultimately, six possible intermediates generated during the sonophotocatalytic process were identified using gas chromatography-mass spectrometry (GCMS).

Highly Efficient and Stable Bifunctional Co3Ni6S8 for Electrocatalytic Oxidation of Benzyl Alcohol and Facilitation of Hydrogen Production

The electrocatalytic oxidation of benzyl alcohol (BAOR) is crucial for promoting green industrial oxidation processes and enhancing the yield and productivity of high-value chemicals. However, there are challenges in this field, such as difficult oxidation steps in alkaline electrolytes, slow reaction kinetics, and difficulty in preserving the activity of catalysts during long-term catalytic reactions. Addressing these issues and achieving synergistic reactions to improve energy utilization by combining hydrogen evolution with enhanced catalyst activity and stability warrants focused investigation. Herein, the study reports a Co3Ni6S8-based catalyst, Co0.33Ni0.67S1-10c, which can achieve the oxidation of benzyl alcohol (BA) in alkaline solution for over 350 h, with a conversion rate of BA exceeding 90% and a Faraday efficiency of benzoic acid (BAA) exceeding 99%. The hydrogen production capacity of Co0.33Ni0.67S1-10c is also evaluated in both three-electrode and dual-electrode systems. In the three-electrode system, the hydrogen evolution rate is enhanced by a factor of 9.59 compared to the absence of BA, while in the dual-electrode system, the rate is increased by a factor of 7.85. This work presents a highly efficient and durable catalyst for the oxidation of BA and its synergistic integration with hydrogen production.

Advances in anion-intercalated layered double hydroxides for supercapacitors: study of chemical modifications and classifications

Hybrid material-based electrochemical supercapacitors (SCs) possessing improved energy density (ED), enhanced stability, high porosity, and a large accessible surface area have attracted attention as promising energy storage devices. SCs also demonstrate excellent specific capacitance (Cs) across various current densities, increased capacitance, and high cell voltages, all contributing to improved ED. Layered double hydroxides (LDHs), with their anionic exchange capabilities and laminar structures, offer significant potential for boosting charge transfer in SCs. This review provides a comprehensive overview of the recent advances in anion-based LDHs, discussing their storage mechanisms, chemical modifications, and classification based on interlayer anions. The roles of different anions, including monovalent, divalent, and polyoxometalates, in enhancing storage properties are examined. In addition, the challenges, future research directions, and practical perspectives of anion-storing LDHs are presented. Hence, this review provides a concise overview of anion-based LDHs for SCs, highlighting their potential significance in energy storage applications.

Growth of Succulent Shaped Fluorine Incorporated Ni─Co LDH (F-NiCo(OH)2): Elevating Supercapacitor Efficiency

The unparalleled morphological tuning of layered double hydroxides (LDHs), specifically NiCo(OH)2, through fluorine doping, is systematically investigated. The unique morphological tuning is achieved by precisely modulating the fluorine dopant concentration using a straightforward solvothermal approach. Field Emission Scanning Electron Microscopy (FESEM) results show distinct succulent-like morphologies in the samples, influencing the surface area and electrochemical performance. Electrochemical studies of the fabricated asymmetric supercapacitor consisting of 2F-NiCo(OH)2|Activated Carbon(AC) electrodes exhibit very high charge storage capacity as high as 402 C g-1. Further, the X-ray photoelectron spectroscopy analysis confirms the incorporation and chemisorption of fluorine within the LDH layers, thereby corroborating its presence influencing the electronic environment and enhancing the electrochemical performance. The device shows an exceptionally high energy density, of 67 Wh kg-1 with power density of 10.6 kW kg-1 while retaining 95% specific capacity after 13 000 cycles at 10 mA cm-2 current density. The practical applicability of the developed supercapacitor is demonstrated by successfully powering an LED and a calculator, underscoring its potential for real-world energy storage solutions.

2D porous hexaniobate-bismuth vanadate hybrid photocatalyst for photodegradation of aquatic refractory pollutants

Metal oxide semiconductors are highly promising due to their excellent photocatalytic performance in the photodegradation of industrial waste containing refractory chemical compounds. A hybrid structure with other semiconductors provides improved photocatalytic performance. In this work, porous and two-dimensional (2D) hexaniobate-bismuth vanadate (Nb6-BiVO4) Z-scheme hybrid photocatalysts are synthesized by chemical solution growth (CSG) of BiVO4 over electrophoretically deposited Nb6 thin films. The structural and morphological analysis of Nb6-BiVO4 hybrid thin films evidenced the well-crystalline uniform growth of monoclinic scheelite BiVO4 over lamellar Nb6 nanosheets. The Nb6-BiVO4 hybrid thin films exhibit a highly porous randomly aggregated nanosheet network, creating the house-of-cards type morphology. The Nb6-BiVO4 hybrid thin films display a strong visible light absorption with band gap energy of 2.29 eV and highly quenched photoluminescence signal, indicating their visible light harvesting nature and intimate electronic coupling between hybridized species beneficial for photocatalytic applications. The visible-light-driven photodegradation performance of methylene blue (MB), rhodamine-B (Rh-B) dyes, and tetracycline hydrochloride (TC) antibiotic over Nb6-BiVO4 hybrid are studied. The best optimized Nb6-BiVO4 thin film shows superior photocatalytic activity for photodegradation of MB, Rh-B dyes, and TC antibiotic with photodegradation rates of 87.3, 92.8, and 64.7 %, respectively, exceptionally higher than that of pristine BiVO4. Furthermore, the mineralization study of Nb6-BiVO4 thin film is conducted using chemical oxygen demand (COD) analysis. The optimized Nb6-BiVO4 thin film shows superior percentage COD removal of 83.33, 85.42, and 61.36 % for MB, Rh-B dyes and TC antibiotic, respectively. The present results highlight the expediency of hybridization in enhancing the photocatalytic activity of pristine BiVO4 by minimizing its charge recombination rate and improving chemical stability.

Facile Synthesis of Mesoporous Nanohybrid Two-Dimensional Layered Ni-Cr-S and Reduced Graphene Oxide for High-Performance Hybrid Supercapacitors

This study describes the single-step synthesis of a mesoporous layered nickel-chromium-sulfide (NCS) and its hybridization with single-layered graphene oxide (GO) using a facile, inexpensive chemical method. The conductive GO plays a critical role in improving the physicochemical and electrochemical properties of hybridized NCS/reduced GO (NCSG) materials. The optimized mesoporous nanohybrid NCSG is obtained when hybridized with 20% GO, and this material exhibits a very high specific surface area of 685.84 m2/g compared to 149.37 m2/g for bare NCS, and the pore diameters are 15.81 and 13.85 nm, respectively. The three-fold superior specific capacity of this optimal NCSG (1932 C/g) is demonstrated over NCS (676 C/g) at a current density of 2 A/g. A fabricated hybrid supercapacitor (HSC) reveals a maximum specific capacity of 224 C/g at a 5 A/g current density. The HSC reached an outstanding energy density of 105 Wh/kg with a maximum power density of 11,250 W/kg. A 4% decrement was observed during the cyclic stability study of the HSC over 5000 successive charge-discharge cycles at a 10 A/g current density. These results suggest that the prepared nanohybrid NCSG is an excellent cathode material for gaining a high energy density in an HSC.