Recent Advances on the Use of Nickel Nano Layered Double Hydroxides as Green, and Efficient, Catalysts for Water Splitting

Hybridization of layered double hydroxides with functional particles

Layered double hydroxides (LDHs) are a class of materials with useful properties associated with their anion exchange abilities as well as redox and adsorptive properties for a wide range of applications including adsorbents, catalysts and their supports, electrodes, pigments, ceramic precursors, and drug carriers. In order to satisfy the requirements for each application as well as to find alternative applications, the preparation of LDHs with the desired composition and particle morphology and post-synthetic modification by the host-guest interactions have been examined. In addition, the hybridization of LDHs with various functional particles has been reported to design materials of modified, improved, and multiple functions. In the present article, the preparation, the heterostructure and the application of hybrids containing LDHs as the main component are overviewed.

Layered Double Hydroxide Catalysts Preparation, Characterization and Applications for Process Development: An Environmentally Green Approach

The adage of new generation of fine chemicals process is the best process applied in the absence of conventional methods. However, many methods use different reaction parameters, such as basic and acidic catalysts, for example oxidation, reduction, bromination, water splitting, cyanohydrin, ethoxylation, syngas, aldol condensation, Michael addition, asymmetric ring opening of epoxides, epoxidation, Wittig and Heck reaction, asymmetric ester epoxidation of fatty acids, combustion of methane, NOx reduction, biodiesel synthesis, propylene oxide polymerization. Layered Double Hydroxides (LDHs) have received considerable attention due their potential applications in flame retardant and has excellent medicinal property for reducing acidity. These catalysts are characterized using analytical techniques, such as: X-ray diffraction (XRD), Fourier-transform infrared (FT-IR), Raman spectroscopy, Thermogravimetric-Differential Thermal Analyzer (TG-DTA), Scanning electron microscope (SEM), Transmission electron microscopes (TEM), Brunauer-Emmett-Teller (BET) surface area, N2 Adsorption-desorption, Temperature programmed reduction (TPR), X-ray photoelectrons spectroscopy (XPS), which gives its overall picture of its structure, porosity, morphology, thermal stability, reusability, and activity of catalysts. LDHs catalysts have proven to be economic and environmentally friendly. The above discussed applications make these catalysts unique from Green Chemistry point of view since they are reusable, and eco-friendly catalysts. Copyright © 2021 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0). 

Transition metal-based layered double hydroxides for photo(electro)chemical water splitting: a mini review

The conversion of solar energy into usable chemical fuels, such as hydrogen gas, via photo(electro)chemical water splitting is a promising approach for creating a carbon neutral energy ecosystem. The deployment of this technology industrially and at scale requires photoelectrodes that are highly active, cost-effective, and stable. To create these new photoelectrodes, transition metal-based electrocatalysts have been proposed as potential cocatalysts for improving the performance of water splitting catalysts. Layered double hydroxides (LDHs) are a class of clays with brucite like layers and intercalated anions. Transition metal-based LDHs are increasingly popular in the field of photo(electro)chemical water splitting due to their unique physicochemical properties. This article aims to review recent advances in transition metal-based LDHs for photo(electro)chemical water splitting. This article provides a brief overview of the research in a format approachable for the general scientific audience. Specifically, this review examines the following areas: (i) routes for synthesis of transition metal-based LDHs, (ii) recent developments in transition metal-based LDHs for photo(electro)chemical water splitting, and (iii) an overview of the structure-property relationships therein.

Cobalt and nitrogen co-doped Ni3S2 nanoflowers on nickel foam as high-efficiency electrocatalysts for overall water splitting in alkaline media

The development of high-performance and cost-effective bifunctional water splitting catalysts has enormous significance in the hydrogen production industry from water electrolysis. Herein, an in situ Co and N co-doping method was developed to improve the electrocatalytic performance of Ni3S2 catalysts. The Co-N-Ni3S2/NF is successfully synthesized for the first time by a one-step hydrothermal method, wherein nickel foam, thioacetamide and Co(NO3)2·6H2O are used as the nickel source, sulfur source, nitrogen source and cobalt source. Co-N-Ni3S2/NF exhibits excellent oxygen evolution reaction activity (an overpotential of 285 mV@50 mA cm-2) and hydrogen evolution reaction activity (an overpotential of 215 mV@10 mA cm-2) in 1 M KOH solution. The electrolytic cell displayed a low cell voltage of 1.50 V when the Co-N-Ni3S2/NF material was used as the bifunctional water splitting electrocatalyst, which is one of the best catalysts reported so far. Density functional theory calculations show that Co-N-Ni3S2/NF exhibits stronger water adsorption energy than those of N-Ni3S2/NF, Co-Ni3S2/NF and Ni3S2/NF. It is proved that the doping of Co and N can effectively regulate the electron cloud density of Ni, thus enhancing the electrochemical activity of Co-N-Ni3S2/NF.

Flower-like Fe-Co-M (M=S, O, P and Se) Nanosheet Arrays Grown on Nickel Foam as High-efficiency Bifunctional Electrocatalysts

The development of highly efficient, inexpensive, abundant and non-precious metal electrocatalysts is the lifeblood of the hydrogen production industry, especially the hydrogen production industry by electrolysis of water. A Fe-Co-S/NF bifunctional electrocatalyst with nanoflower-like structure was synthesized on three-dimensional porous nickel foam through one-step hydrothermal and one-step high-temperature sulfuration operations, and the material displays high-efficiency electrocatalytic performance. As a catalyst for the hydrogen evolution reaction, Fe-Co-S/NF can drive a current density of 10 mA/cm² at an overpotential of 143 mV with a Tafel slope of 80.2 mV/dec. When it was used as an oxygen evolution reaction catalyst, it exhibits good OER reactivity with a low Tafel slope (82.6 mV/dec) and with requiring only 117 mV overpotential to drive current densities up to 50 mA/cm² . In addition, the Fe-Co-S/NF//Fe-Co-S/NF electrolytic cell was assembled, an electrolysis voltage of 1.64 V is required to drive a current density of 50 mA/cm² , which is one of the most active catalysts reported so far. This work indicates that the introduction of S, P and Se treating processes could effectively improve electrical conductivity of the material and enhance the catalytic activity of the material. This work offers an effective and convenient method for improving the morphology of the catalyst, increasing the surface area of the catalyst and developing high-efficiency and low-cost catalysts.

Construction of hierarchical layered hydroxide grown in situ on carbon tubes derived from a metal-organic framework for asymmetric supercapacitors

Electrode materials are very important for the performance of supercapacitors (SCs). Therefore, preparation of hybrid electrode materials is an effective way to develop high-performance SCs. We firstly design and prepare metal organic framework (MOF) derived carbon nanotubes as the core skeleton to support the shell of a nickel gallium layered hydroxide nanosheet (NiGa-LDH). MOF derived carbon nanomaterials have high conductivity and a large specific surface area, which can promote electron transfer and improve the agglomeration of LDH. The deposited LDH can provide high specific capacitance and the layered structure can further enhance the reaction site. The NiGa-LDH@CNT-500@CC has an excellent specific capacitance of 2580 F g-1 at 1 A g-1 and a high capacitance retention rate of 83.3% at 5 A g-1 due to the synergistic effect of two materials. The assembled NiGa-LDH@CNT-500@CC//carbon NS asymmetric supercapacitor (ASC) has an operating voltage of 1.6 V and a high energy density of 52 W h kg-1 at a power density of 952 W kg-1. Therefore, the core-shell structure composed of LDH and carbon nanomaterials provides an effective way for the design of high-performance electrodes.

Recent Progress on NiFe-Based Electrocatalysts for the Oxygen Evolution Reaction

The seriousness of the energy crisis and the environmental impact of global anthropogenic activities have led to an urgent need to develop efficient and green fuels. Hydrogen, as a promising alternative resource that is produced in an environmentally friendly and sustainable manner by a water splitting reaction, has attracted extensive attention in recent years. However, the large-scale application of water splitting devices is hindered predominantly by the sluggish oxygen evolution reaction (OER) at the anode. Therefore, the design and exploration of high-performing OER electrocatalysts is a critical objective. Considering their low prices, abundant reserves, and intrinsic activities, NiFe-based bimetal compounds are widely studied as excellent OER electrocatalysts. Moreover, recent progress on NiFe-based OER electrocatalysts in alkaline environments is comprehensively and systematically introduced through various catalyst families including NiFe-layered hydroxides, metal-organic frameworks, NiFe-based (oxy)hydroxides, NiFe-based oxides, NiFe alloys, and NiFe-based nonoxides. This review briefly introduces the advanced NiFe-based OER materials and their corresponding reaction mechanisms. Finally, the challenges inherent to and possible strategies for producing extraordinary NiFe-based electrocatalysts are discussed.