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Electrochemistry of Porous Oxides and Related Materials
Published in Antonio Doménech-Carbó, Electrochemistry of Porous Materials, 2021
Layered double hydroxides (LDHs) of Al, Ni, Zn, and other metals are composed by rigid layers where anions and water molecules can move. Typical layered double hydroxides can be represented by the formula [M1–xM′x(OH)2][An−]x/n·mH2O, where M is a divalent metal cation, M′ could be a trivalent metal cation or a mix of trivalent and divalent metal cations, and An– represents an interlayer anion or mix of anions. Both divalent and trivalent cations are located at the center of octahedral composed of OH– ions; M(OH)6 and M′(OH)6 units share edges forming two-dimensional layers while the interlayer space incorporates anions (and water molecules) to maintain electroneutrality. These materials exhibit a stable lamellar structure (see scheme in Figure 8.5) while 0.2 ≤ x ≤ 0.5, and the interlamellar An– anions can be freely exchanged by foreign anions [17,18]. Figure 8.2 depicts a schematic representation of LDHs.
Anion Exchange Membrane Water Electrolysis
Published in Lei Zhang, Hongbin Zhao, David P. Wilkinson, Xueliang Sun, Jiujun Zhang, Electrochemical Water Electrolysis, 2020
Ya Yan, Bao Yu Xia, Hongbin Zhao, Muhammad Arif Khan
Layered double hydroxides (LDHs), a kind of hydrotalcite-like compound, are a large category of 2D anionic clay materials. To date, a broad collection of LDHs such as binary ZnCo, CoCo, CoFe, NiCo, NiFe, and LiFe and ternary FeNiCo and NiFeMn have been developed for water oxidation electrocatalysts [69–76]. In particular, LDH materials containing Fe usually exhibited much higher activity for the OER. Many studies have indicated that NiFe LDHs exhibit the best performance among various LDH materials by comparing the OER activity of NiFe LDH with other LDH materials. Recently, Sun et al. [74] reported a Ni-Fe-Mn ternary LDH, experimental results showed that the obtained Ni-Fe-Mn LDHs exhibit higher OER activity than that of NiFe LDH and commercial Ir-based catalysts. It is found that the electronic structure of the material has been adjusted after doping the layered structure with the Mn4+ ions, which also improves the electrical conductivity. Additionally, the limited conductivity and low specific surface area for the NiFe-based LDHs can be optimized by growing vertically aligned nano-structures on conductive substrates, such as conductive novel carbon materials.
Dimensionality Transformation of Layered Materials toward the Design of Functional Nanomaterials
Published in Kazuhiro Shikinaka, Functionalization of Molecular Architectures, 2018
Layered materials accommodate various ions and molecules, and the intercalation properties are also able to be modified by the formation of 0D nanoparticles. Layered double hydroxides (LDHs) are anion exchanging layered compounds [91]. The brucite sheet of LDHs consists of divalent cations, and a part of them is substituted with trivalent cations, resulting in the formation of permanent positive layer charge. Charge compensating anions and water molecules are present in the interlayer gallery. Because of the anion exchangeability, LDHs are useful as scavenger for harmful anionic species. However, the anion exchangeability is c because of the irreversible inclusion of CO2– originating from CO, which limits their use under practical conditions. Decarbonation requires exclusion of CO2 and use of additives [92–94].
Two-dimensional materials beyond graphene for the detection and removal of antibiotics: A critical review
Published in Critical Reviews in Environmental Science and Technology, 2022
Lingxia Lu, Qi Yang, Qing Xu, Yongjun Sun, Susu Tang, Xiaobin Tang, Heng Liang, Yadong Yu
Layered double hydroxides (LDHs) are anionic clays that contain positively charged ionic groups on the layers and negatively charged anions in the interlayer regions. The general formula of LDHs is [M2+1-xM3+x(OH−)2][An−]x/n·zH2O (x = –0.2–0.4), where M2+ and M3+ are divalent and trivalent metal cations, respectively, and An− is the inorganic or organic anion (Goh et al., 2008) (Figure 3E). The chemical composition of LDHs is tunable, and the incorporation of suitable photoactive transition metals (e.g., Zn, Ti, Fe) in the structure of LDHs has yielded effective photocatalysts that have been used in antibiotic photodegradation (Table S3). The structural characteristics, such as large surface area, and high anion-exchange capacity (2–3 meq/g) of LDHs make them useful adsorbent materials for many anionic species (Cornejo et al., 2008; Sepehr et al., 2017).
Phosphorus pollution control using waste-based adsorbents: Material synthesis, modification, and sustainability
Published in Critical Reviews in Environmental Science and Technology, 2022
Hongxu Zhou, Andrew J. Margenot, Yunkai Li, Buchun Si, Tengfei Wang, Yanyan Zhang, Shiyang Li, Rabin Bhattarai
Layered double hydroxides (LDHs) are composed of positively charged metal hydroxide layers, including the divalent cation (Fe2+, Mg2+, Ni2+, and Mn2+) or trivalent cation (Fe3+, Al3+, and Cr3+) and the interlayer anion (CO32−, SO42−, OH−, and Cl−) along with water molecule (Yang, Zhang, et al., 2019). Immense interests have shown by scientists to assemble LDHs with biochar to manufacture mineral-biochar composites, and the resulting biochar/LDH composites exhibit significant improvement in the physicochemical and adsorption characteristics (Peng et al., 2021). Yang, Zhang, et al. (2019) prepared Al/Mg-modified biochar (feedstock: corn stalks biomass) with a P adsorption capacity of 152 mg g−1. In another study, Peng et al. (2019) applied response surface methodology (RSM) to optimize the production of synthesized Fe/Al (Hydr)oxides-Biochars (feedstocks: almond shell, corn stalk, and dairy manure) for the P removal. These Fe/Al (hydr)oxides-Biochars presented excellent P adsorption capacities (ranged from 180 to 215 mg P g−1) due to a good amount of surface area, pore volume, and reactive surface hydroxyl sites.
Synthesis and characterization of zinc-aluminum based layered double hydroxide and oxide nanomaterials by performing different experimental parameters
Published in Journal of Dispersion Science and Technology, 2022
Layered double hydroxides (LDHs) are famous group of layered materials known as anionic clays, as well as positively charged hydrotalcite-like compounds. LDHs are represented by the general formula where M2+ and M3+ are divalent and trivalent cations, respectively and An− is the intercalated anion.[1] LDHs are synthesized in several contents like ZnAl-X-LDHs (X = Cl−, or ),[2] graphene oxide modified ZnAl-LDH,[3] SnO2–ZnAl-LDH,[4] ZnAl-SO4-LDH,[5] CoNiAl-LDH nanocomposite,[6] Cu0.35Ni0.31Fe0.34-LDH, Cu0.33Zn0.32Cr0.35-LDH,[7] and so forth with several preparation methods to apply for series important purposes. The most common method for the preparation of LDH is coprecipitation and urea hydrolysis technique that can be produced with high crystallinity.