Alkoxide-intercalated CoFe-layered double hydroxides as precursors of colloidal nanosheet suspensions: structural, magnetic and electrochemical properties

摘要

Alkoxide-intercalated CoFe-layered double hydroxides (CoFe-LDHs) were synthesized via the nonaqueous methanolic route. According to powder X-ray diffraction and field emission scanning electron microscopy, they exhibit a nanosized plate-like morphology with a basal space of 9.21 A. The hydrolysis of the material in water leads to colloidal suspensions of nanosheets with lateral dimensions of about 20 nm and thicknesses of ca. 4 nm as demonstrated by atomic force microscopy and dynamic light scattering. Atomic resolution scanning transmission electron microscopy combined with electron energy-loss spectroscopy confirm the high crystalline quality of the crystals and the proper Co/Fe stoichiometry. The magnetic properties of the CoFe-LDH have been investigated by means of DC and AC magnetic susceptibility measurements and isothermal magnetisation, showing a low-temperature magnetic ordering below ca. 7 K with a size-dependent spin-glass like behaviour, and displaying hysteresis cycles at 2 K with a coercive field of 402 G. Moreover, the sample has been tested as an electrode material for supercapacitors in a three-electrode system by means of cyclic voltammetry and galvanostatic charge-discharge experiments, showing high capacitances and stability. Finally, we have explored the electrocatalytic behaviour towards water oxidation, demonstrating its efficient and persistent performance at basic pHs, highlighting their tremendous potential in energy storage devices.