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) are promising supercapacitor materials due to their wide chemical versatility, earth abundant metals and high specific capacitances. Many parameters influencing the supercapacitive performance have been studied such as the chemical composition, the synthetic approaches, and the interlayer anion. However, no systematic studies about the effect of the basal space have been carried out. Here, two‐dimensional (2D) CoAl‐LDHs were synthesized through anion exchange reactions using surfactant molecules in order to increase the interlayer space (ranging from 7.5 to 32.0 Å). These compounds exhibit similar size and dimensions but different basal space to explore exclusively the interlayer distance influence in the supercapacitive performance. In this line, Co : Al ratios of 2 : 1, 3 : 1 and 4 : 1 were explored. In all cases, an enhancement of the specific capacitance was observed by increasing the basal space, reaching ca. 50 % more than the value obtained from the less‐spaced 2 : 1 CoAl‐LDH (going from ca. 750 to 1100 F.g−1 at 1 A.g−1). This increment mainly occurs because of the increase in the electrochemical surface area (up to ca. 260 %) and the higher electrolyte diffusion. Interestingly, the best performance is achieved for the lowest Co : Al ratio (i. e. the highest Al content) revealing the important role of the electrochemically inert Al in the structure.

Layered double hydroxides (LDHs) are ac lass of 2D anionic materials exhibiting wide chemical versatility and promising applications in different fields, ranging from catalysis to energy storage and conversion.H owever,t he covalent chemistry of this kind of 2D materials is still barely explored. Herein, the covalentf unctionalization with silanes of am agnetic NiFe-LDH is reported. The synthetic route consists of at opochemical approach followed by anion exchange reaction with surfactant molecules prior to covalent functionalization with the (3-aminopropyl)triethoxysilane (APTES) molecules. The functionalized NiFe-APTES was fully characterized by X-ray diffraction, infrared spectroscopy, electron microscopy,t hermogravimetric analysis coupled with mass spectrometry and 29 Si solid-state nuclear magnetic resonance, among others. The effect on the electronic properties of the functionalizedL DH was investigated by am agnetic study in combination with Mçssbauer spectroscopy. Moreover,t he reversibility of the silane-functionalizationa t basic pH was demonstrated, and the quality of the resulting LDH was proven by studying the electrochemical performance in the oxygen evolution reaction in basic media. Furthermore, the anion exchange capability for the NiFe-APTES was tested employing Cr VI ,r esulting in an increase of 200 %o ft he anion retention. This report allows for an ew degree of tunability of LDHs, openingt he door to the synthesis of new hybrid architectures and materials.[a] Dr.Figure 2. FESEM (A), TEM (B) and mapping images (bottom panel) of NiFe-APTES. The inset in (A) shows DLS and the inset in (B) showst he SAED pattern. Mapping imagesare obtained from the single particle in the bottom left image( scale bar of 100 nm).