Alkoxide-intercalated CoFe–LDHs have been successfully synthesized and characterized, showing size-dependent magnetism, supercapacitive properties and excellent water oxidation electrocatalytic behaviour.

Layered double hydroxides (LDHs) are low dimensional materials that act as benchmark catalysts for the oxygen evolution reaction (OER). Many LDH properties affecting the OER have been studied to reach the optimal efficiency but no systematic studies concerning the influence of the interlayer space have been developed. In this context, these materials allow a large tunability in their chemical composition enabling the substitution of the interlayer anion and therefore modifying exclusively the basal space. Here, we synthesize by anion exchange reactions a surfactantintercalated family of NiFe-LDHs with increasing basal spacing ranging from 8.0 to 31.6 (one of the largest reported so far for a NiFe-LDH) while the electrochemical OER performance of this family of compounds was explored to analyse the interlayer distance effect keeping similar morphology, dimensions and metallic composition. Results show the increase of the LDH basal space undergo to lower Tafel slopes, higher electrochemical surface area and a reduction of the resistance related to the chemisorption of oxygen leading to better kinetic behaviour, showing an optimum enhancement of the electrocatalytic performance for the NiFe-dodecyl sulphate (basal space of 25 ). Interestingly, the NiFe-dodecyl sulphate exhibits optimum proton diffusion values, indeed a further increment in the basal space compromises the onset potential, a fact that could be related to an increase in the hydrophobicity between the layers. Moreover, by judicious tuning of the interlayer space, it is possible to reach a Tafel slope value for the most spaced LDH (NiFe-octadecyl sulphate, basal space of 31.6 ), similar to the one obtained for exfoliated NiFe nanosheets, showing a much better long-time stability due to the three-dimensional robustness of the catalysts. This work illustrates the importance of molecular engineering in the design of novel highly active catalysts and provides important insights into the understanding of basic principles of oxygen evolution reaction in NiFe-LDHs.

Layered double hydroxides (LDHs) exhibit unparalleled anion exchange properties and the ability to be exfoliated into 2D nanosheets, which can be used as a building block to fabricate a wide variety of hybrid functional nanostructured materials. Still, if one wants to use LDHs as a magnetic building blocks in the design of complex architectures, the role played by the dipolar magnetic interactions in these layered materials needs to be understood. In this work, we synthesized and characterized a five-membered CoAl-LDH series with basal spacing ranging from 7.5 to 34 Å. A detailed experimental characterization allows us to conclude that the main factor governing the dipolar interactions between magnetic layers cannot be the interlayer spacing. Supporting theoretical modeling suggests instead a relevant role for spin correlation size, which, in the limit, is related to the lateral dimension of the layer. These results highlight the importance of cation ordering in the magnetic behavior of LDHs, and underpin the differences with homometallic-layered hydroxides.

a Alkoxide-intercalated NiFe-layered double hydroxides were synthesized via the nonaqueous methanolic route. These nanoplatelets exhibit high crystalline quality as demonstrated by atomic resolution scanning transmission electron microscopy combined with electron energy-loss spectroscopy. Moreover, the presence of the alkoxide moieties has been unambiguously demonstrated by means of thermogravimetric analysis coupled to a mass spectrometer. These NiFe-LDHs can be exfoliated in water or organic solvents and processed into homogeneous ultra-thin films (<3 nm thick) with the assistance of O 2 -plasma. The study of their behaviour as water oxidation electrocatalysts has shown an outstanding performance at basic pHs (small overpotential of ca. 249 mV and Tafel slopes in the range of 52-55 mV per decade).

Some recent reports claiming room temperature spontaneous magnetization in layered double hydroxides (LDHs) have been published; however, the reported materials cause serious concern as to whether this cooperative magnetic behavior comes from extrinsic sources, such as spinel iron oxide nanoparticles. The syntheses of crystalline Fe(3+)-based LDHs with and without impurities have been developed, highlighting the care that must be taken during the synthetic process in order to avoid misidentification of magnetic LDHs.

The synthesis of ultrathin films (UTFs) of NiFe‐LDHs has been achieved by means of an in situ hydrothermal approach, leading to a flat disposition of the LDH crystallites on the substrate, in clear contrast to the most common perpendicular orientation reported to date. Experimental factors like time of synthesis or the nature of the substrate, seem to play a crucial role during the growing process. The 2D morphology of the NiFe‐LDH crystallites was kept after a calcination procedure, leading to a topotactic transformation into mixed‐metal oxide platelets. Hereby, in order to study the catalytic behavior of our samples, a chemical vapor deposition process is explored upon the as‐synthesized films. In presence of a carbon source (ethylene), these films catalyze a preferential low‐temperature (550 °C) growth of bamboo‐like carbon nanotubes, in stark contrast to the different mixture of carbon nanoforms obtained from the bulk samples. This work opens the door for the development of UTFs based on LDHs, which may be of utmost importance in a wide range of potential applications ranging from magnetic storage, catalysis or biomedical applications, to electrochemical batteries, anti‐corrosion and superhydrophobic coatings.

We report the synthesis of magnetic CoAl and NiFe layered double hydroxides endowed with well-defined morphology (hexagonal and flower-like shapes) and how the distortion of the nanosheets influences their magnetic properties.

Direct exfoliation of carbonate layered double hydroxides has been achieved by using a novel horn-probe sonic tip, avoiding the development of time-consuming anion-exchange reactions.