Facile topochemically prepared hierarchical Ni–Fe LDH nanoflowers for the electrochemical oxygen elution reaction

Abstract

Here we report a simple topochemical method to prepare Ni–Fe layered double hydroxide (LDH). Ni(II)Fe(II) hydroxide was prepared via coprecipitation of Ni²⁺ and Fe²⁺ by NH₄HCO₃ under anaerobic conditions at room temperature. Ni–Fe LDH was obtained via oxidation intercalation by exposing the precipitate to air. The structure of the LDH was characterized and the performance in the electrochemical oxygen elution reaction (OER) was determined. Residual Fe(II) was observed by XPS due to incomplete oxidation, resulting in Fe replacing the Ni site in the LDH. It is found that LDH embedded with both Fe–O–Fe and Ni–O–Fe moieties is beneficial to the OER in terms of a low overpotential (240 mV at 10 mA cm⁻²), small Tafel slope (25 mV dec⁻¹) and high electrochemical stability.