Layered double hydroxides (LDH) is a large family of chemical compounds exhibiting a wide composition variety which results in many possible applications such as catalysts, antacids or flame retardants. LDHs have a structure similar to that of brucite, where single layers are made of edge sharing Mg(OH)6 octahedrons. Contrary to brucite, the layers of LDH present a net positive charge resulting from the partial substitution of divalent cations with trivalent ones. In order to ensure overall electrical charge neutrality, anions are intercalated within the interlayer space, which results in electrostatic interactions between the layers. These forces together with van der Waals interactions and hydrogen bonds keep the sheets together to form a three-dimensional layered framework. Recently, a special attention has been placed on Ni-Fe LDH, which has shown a great potential as electrocatalyst in oxygen evolution reaction (OER). Moreover, it was also suggested that Ni-Fe LDH catalytic activity is related not only to the surface area, but also to the number of open coordination sites at the edges, so the design of simple synthesis routes for the preparation of Ni-Fe LDH is crucial in order to achieve reliable and highly active electrocatalysts. In this work, we present a simple synthesis method to produce pure and highly crystalline Ni-Fe LDH hexagonal platelets at a relatively low temperature of 100 oC carried out in a conventional round bottom flask with upscaling possibilities. Additionally, we have analyzed the reaction intermediates and proposed a possible formation mechanism of the Ni-Fe LDH platelets. Furthermore, advanced microscopic characterization let us understand the material properties and its stability at elevated temperature. Finally, an OER overpotential value electrochemically measured was 0.36 V with potential improvement via post-processing treatment.

Synthesis and investigation into the formation mechanism of Ni-Fe layered double hydroxides for oxygen evolution reaction

256th National Meeting (2018)

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