The Cu2O/ZnTi-LDH (Cu2O/LDH) composite was synthesized via Cu-doping into the ZnTi-LDH followed by in-situ reduction strategy for Cr(VI) reduction and tetracycline (TC) degradation under ...visible-light, where the Cu2O nanoparticles (NPs) were homogeneously embedded onto the LDH host layers through in-situ reducing the Cu-doped ZnTi-LDH (CuZnTi-LDH). The optical, photoelectric and photocatalytic performances of the Cu2O/LDH could be adjusted by changing the Cu-doping amount in the CuZnTi-LDH. As expected, the optimal Cu2O/LDH0.10 exhibited high photocatalytic activities for the Cr(VI) reduction (95.5% Cr(VI) removal) and TC degradation (71.6% TC removal) after 120 min. Based on the experimental and density functional theory (DFT) calculation results, a possible p-n heterostructure formation between Cu2O and ZnTi-LDH as well as the transfer route of photogenerated electron-hole pairs toward for Cr(VI) reduction and TC degradation were proposed. This work may provide a rational and facile strategy for improving the LDH-based materials in catalytic oxidation-reduction reactions.
The schematic diagram of the evolution process of the Cu2O/ZnTi-LDH, and photocatalytic of Cr(VI) reduction and TC degradation under visible-light. Display omitted
•Cu2O NPs were evenly embedded onto the LDH host layers by in-situ reduction strategy.•Cu2O self-photooxidation was restrained due to the high dispersion of Cu2O NPs.•The p-n heterostructure provided a new path for transfer and separation of electron-hole pairs.•Cu2O/ZnTi-LDH displayed excellent Cr(VI) reduction and TC degradation performances.
•A novel layered Ta doped NiFe LDH for electrochemical water splitting catalysis.•Intrinsic electron transfer from Fe to Ta was observed in Ta-NiFe LDH.•The increased activity of OER is due to the ...low coordination state at the Ta-doping site.
Structural manipulation of electrocatalyst via doping strategy has always held great interests for developing advanced and stable non-noble metal electrocatalyst for oxygen evolution reaction (OER). Herein, a high-valence state tantalum (Ta) was incorporated into the pristine NiFe layered double hydroxide (LDH) by hydrothermal method. Interestingly, as revealed by structural characterizations, Ta doping causes the lattice expansion of LDH and electronic structure modification through electron transfer from Fe to Ta. DFT calculations further verified that the modulated electronic structure among Ni, Fe and Ta and the modified eg orbital of Ta induced by charge transfer are beneficial for the adsorption of OH species on Ta site in Ta-doped NiFe LDH and increasing the intrinsic metallic property of NiFe LDH. Consequently, the Ta site has lower overpotential compared with other sites on NiFe LDH including the pristine oxygen vacancies, which can improve the electrocatalytic activity for OER. Furthermore, the optimized Ta-NiFe LDH (0.5:6:1.5) exhibited a superior OER activity in contrast to bimetallic LDH, with a low overpotential of 260 mV to drive the current density of 50 mA·cm−2 and a small Tafel slope of 58.95 mV·dec-1. This work provides the theoretical basis for the enhancement of electrochemical OER activity by doping LDH with high-valence state foreign metal.
As a promising bifunctional electrocatalyst for water splitting, NiFe-layered double hydroxide (NiFe LDH) demonstrates an excellent activity toward oxygen evolution reaction (OER) in alkaline ...solution. However, its hydrogen evolution reaction (HER) activity is challenged owing to the poor electronic conductivity and insufficient electrochemical active sites. Therefore, a three-dimensional self-supporting metal hydroxide/oxide electrode with abundant oxygen vacancies is prepared by electrodepositing CeO x nanoparticles on NiFe LDH nanosheets. According to the density functional theory calculations and experimental studies, the oxygen vacancies at the NiFe LDH/CeO x interface can be introduced successfully because of the positive charges accumulation resulting from the local electron potential difference between NiFe LDH and CeO x . The oxygen vacancies accelerate the electron/ion migration rates, facilitate the charge transfer, and increase the electrochemical active sites, which give rise to an efficient activity toward HER in alkaline solution. Furthermore, NF@NiFe LDH/CeO x needs a lower potential of 1.51 V to drive a current density of 10 mA cm–2 in overall water splitting and demonstrates a superior performance compared with the benchmark Pt/C and RuO2, which is indicated to be a promising bifunctional electrode catalyst.
Nanocontainers encapsulating corrosion inhibitors are commonly incorporated into organic coatings to enable self-healing effects, thereby ensuring long-term anticorrosion performance. In this study, ...a novel dual corrosion inhibitor-loaded self-healing nanocontainer with core-shell structure was proposed for fabricating composite waterborne epoxy coatings with both active and passive corrosion prevention properties.
The nanocontainer, named BTA-ZIF-8@LDH-Mo, was synthesized through the in-situ growth of molybdate-intercalated ZnAl layered double hydroxide (LDH-Mo) on the surface of 1H-benzotriazole-inbuilt zeolitic imidazolate framework (BTA-ZIF-8). Potentiodynamic polarization results showed that the Icorr of bare Q235 carbon steel immersed in a 3.5 wt% NaCl solution decreased from 4.658 × 10−6 A/cm2 to 1.274 × 10−6 A/cm2 after introducing BTA-ZIF-8@LDH-Mo nanocontainers, resulting in a superior corrosion inhibition efficiency of 72.65 %. Electrochemical impedance spectroscopy further demonstrated that the |Z|f=0.01Hz of epoxy coating doped with BTA-ZIF-8@LDH-Mo reached 4.24 × 109 Ω·cm2 after 42 d of immersion in 3.5 wt% NaCl solution, approximately 30 times higher than that of pure EP coating. Moreover, investigations on artificially scratched coatings indicated that the incorporation of BTA-ZIF-8@LDH-Mo nanocontainers effectively mitigated the corrosion process by forming an inhibiting layer on the metal substrate that impeded the corrosion process. The dual corrosion inhibitor strategy relies on the synergistic action of BTA pre-loaded in ZIF-8 nanoparticles and molybdate (MoO42-) intercalated in LDH interlayers for active corrosion protection. Additionally, the nanocontainers enhance passive protection by elongating the diffusion paths of corrosive media and trapping chloride ions. This nanocontainer design offers a facile strategy for fabricating a smart coating with the excellent anticorrosion properties.
•BTA-ZIF-8@LDH-Mo core-shell structured nanocontainers were prepared.•Resulted nanocontainers exhibited effective dual inhibitor release.•The nanocontainers provide both active and passive corrosion protection for waterborne epoxy coating.
Layered double hydroxides (LDHs) have been considered as promising electrodes for supercapacitors due to their adjustable composition, designable function and superior high theoretic capacity. ...However, their experimental specific capacity is significantly lower than the theoretical value due to their small interlayer spacing. Therefore, obtaining large interlayer spacing through the intercalation of large‐sized anions is an important means to improve capacity performance. Herein, a metal organic framework derived cobalt‐nickel layered double hydroxide hollowcage intercalated with different concentrations of 1,4‐benzenedicarboxylic acid (H2BDC) through in‐situ cationic etching and organic ligand intercalation method is designed and fabricated. The superior specific capacity and excellent rate performance are benefit from the large specific surface area of the hollow structure and increasing interlayer spacing of LDH after H2BDC intercalation. The sample with the largest layer spacing displays a maximum specific capacity of 229 mA h g−1 at 1 A g−1. In addition, the hybrid supercapacitor assembled from the sample with the largest layer spacing and active carbon electrode has a maximum specific capacity of 158 mA h g−1 at 1 A g−1; the energy density is as high as 126.4 W h kg−1 at 800 W kg−1 and good cycle stability.
CoNi‐BDC hollowcage is obtained by intercalating H2BDC ligand into the CoNi‐LDH nanocage through in‐situ cationic etching and organic ligand intercalation methods for the first time. The structure design and engineering strategies of molecular layer spacing regulation endow larger specific surface areas and increase the interlayer spacing of CoNi‐LDH, thereby evidently boosting their electrochemical performance.
Oxygen evolution reaction (OER) is a significant half-reaction in varied energy conversion devices. Ni-based layered double hydroxides (LDHs) have attracted immense attention recently for OER. ...Herein, we have provided a comprehensive overview of the recent development of the Ni-based LDHs for OER. We firstly introduced some fabrication strategies and in situ characterization followed by some typical Ni-based LDHs as electrocatalysts for OER. Then the structure modifications such as exfoliation, layer composition tuning, interlayer space adjustment and integrating Ni-based LDHs with complementing functional materials were overviewed. Some obstacles that hinder the practical applications of Ni-based LDHs were also discussed and it was pointed out that more efforts should be given to structure rational design and the catalyst application in the real water electrolysis technique. This review can help readers understand the recent development of the Ni-based LDHs and get some insights into the rational design of Ni-based LDHs catalyst and catalytic performance improvement strategy.
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•Ni-based LDHs were reviewed for oxygen evolution reaction.•Fabrication strategy and in situ characterization overview for some typical Ni-based LDHs materials.•Structure modification and activity correlation for Ni-based LDHs materials.•Problems and challenges for practical application of Ni-based LDHs.
Seawater electrolysis is an extremely attractive approach for harvesting clean hydrogen energy, but detrimental chlorine species (i.e., chloride and hypochlorite) cause severe corrosion at the anode. ...Here, we report our recent finding that benzoate anions-intercalated NiFe-layered double hydroxide nanosheet on carbon cloth (BZ-NiFe-LDH/CC) behaves as a highly efficient and durable monolithic catalyst for alkaline seawater oxidation, affords enlarged interlayer spacing of LDH, inhibits chlorine (electro)chemistry, and alleviates local pH drop of the electrode. It only needs an overpotential of 320 mV to reach a current density of 500 mA·cm–2 in 1 M KOH. In contrast to the fast activity decay of NiFe-LDH/CC counterpart during long-term electrolysis, BZ-NiFe-LDH/CC achieves stable 100-h electrolysis at an industrial-level current density of 500 mA·cm–2 in alkaline seawater. Operando Raman spectroscopy studies further identify structural changes of disordered δ (NiIII-O) during the seawater oxidation process.
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•V-doped ZnFe LDH was synthesized by co-precipitation.•V doping to ZnFe LDH increased the sonocatalytic removal of pymetrozine by 32%.•The synergy factor of the sonocatalytic process ...using V-doped ZnFe LDH was 7.17.•O2•−, h+ and •OH took part in the sonocatalytic degradation of pymetrozine.•The V-doped ZnFe LDH presented high activity stability for five repetitive runs.
In ultrasonic (US) processes, the development of environmentally friendly, effective, low-cost, and durable catalysts is needed to degrade pollutants. Here, ZnFe layered double hydroxide (LDH) was doped with vanadium (V) for the sonocatalytic degradation of a pesticide pymetrozine. The resulting catalyst had an average thickness of 25 nm, a specific surface area of 125.38 m2/g, and a bandgap value of 2.20 eV. In 90 min ultrasonic treatment, V-doped ZnFe LDH had 73% pymetrozine removal efficiency, which was 32% more than that of undoped ZnFe LDH. The US/V-doped ZnFe LDH process had a strong synergistic effect (synergy factor 7.17), which resulted in 57% and 68% greater efficiencies than the US alone and V-doped ZnFe LDH alone, respectively. The role of radical oxygen species was confirmed by carrying out radical trapping experiments using different scavengers and electron paramagnetic resonance analyses. Due to its high stability, the catalyst had good reuse potential with only an 8% performance reduction after 5 reuse cycles. Besides, the leaching of heavy metals was insignificant owing to the high integrity of the catalyst as confirmed by SEM and X-ray diffraction analysis. According to the GC–MS analysis, pymetrozine was first transformed into cyclic compounds then into aliphatic compounds such as animated products and carboxylic acids.
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•The high adsorption capacity of A-LDH is due to the metal-chelating function.•The reactive sites in ATMP are firstly revealed by Multiwfn calculation.•The non-covalent interactions ...of water/clay interface are firstly presented by IGM.•IGM analysis confirmed that ATMP/LDH is combined together mainly by H-bond.•The reactive sites and non-covalent interactions support experimental results.
Phosphonates are environmental friendly materials, and can be potentially employed to improve the removal efficiency of the clay materials. In the present work, Zn-Al layered double hydroxide (LDH) intercalated with amino trimethylene phosphonic acid (ATMP) by a facile technique and employed as an adsorbent for Cu2+ and Pb2+ from wastewater. The adsorption characteristics and microscopic mechanism of ATMP in the interlayer space were explored by a combination of experimental and density functional theory (DFT). The adsorption capacity for Cu2+ and Pb2+ could reach 42.02 mg.g−1 and 84.06 mg.g−1, respectively. The adsorption kinetics curves were matched well with the pseudo-second-order model, indicating chemical adsorption via electrostatic interaction mechanism. Based on Multiwfn and VMD program calculation, the ways of electrostatic potential and average local ionization energy were firstly applied to predict reactive sites of ATMP molecule and corresponding anion, suggesting that anion state was more easily to provide lone pair electrons for electrophilic reaction. The weak interaction analysis indicated that interactions among ATMP and LDH are mainly dominated by H-bond. These results recommended that modified LDH can be a promising adsorbent for the adsorption of toxic metal ions in practical applications.
Exploring highly active and inexpensive bifunctional electrocatalysts for water‐splitting is considered to be one of the prerequisites for developing hydrogen energy technology. Here, an efficient ...simultaneous etching‐doping sedimentation equilibrium (EDSE) strategy is proposed to design and prepare hollow Rh‐doped CoFe‐layered double hydroxides for overall water splitting. The elaborate electrocatalyst with optimized composition and typical hollow structure accelerates the electrochemical reactions, which can achieve a current density of 10 mA cm−2 at an overpotential of 28 mV (600 mA cm−2 at 188 mV) for hydrogen evolution reaction (HER) and 100 mA cm−2 at 245 mV for oxygen evolution reaction (OER). The cell voltage for overall water splitting of the electrolyzer assembled by this electrocatalyst is only 1.46 V, a value far lower than that of commercial electrolyzer constructed by Pt/C and RuO2 and most reported bifunctional electrocatalysts. Furthermore, the existence of Fe vacancies introduced by Rh doping and the typical hollow structure are demonstrated to optimize the entire HER and OER processes. EDSE associates doping with template‐directed hollow structures and paves a new avenue for developing bifunctional electrocatalysts for overall water splitting. It is also believed to be practical in other catalysis fields as well.
Etching‐doping sedimentation equilibrium induces the conversion of zeolitic imidazolate framework‐67 nanotriangles into template‐directed hollow Rh‐doped CoFe‐layered double hydroxides, which can combine the effects of doping and the synthesis method of etching precursor to accelerate the kinetics for water splitting. These findings provide a new avenue for the combination of doping and template‐directed hollow structures.
