Tailoring nanostructured NiFe-LDH catalysts via ammonium fluoride-mediated hydrothermal synthesis: enhanced electrocatalytic performance in oxygen evolution reactions

Abstract

The performance of NiFe-layered double hydroxides (LDHs) as electrocatalysts for the oxygen evolution reaction (OER) can be significantly enhanced through precise structural and compositional modifications. In this study, ammonium fluoride (NH₄F) was introduced as an effective reagent to tune the microstructure and cation distribution of NiFe-LDHs, which in turn influenced their OER activity. Through a one-step hydrothermal synthesis method, NiFe-LDHs were fabricated with varying amounts of NH₄F. The X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analysis revealed a shift in the oxidation states of Ni and Fe, with an increase in the proportion of high-valent cations in the NFL-7F sample. This shift was closely correlated with enhanced OER performance. Detailed characterization through scanning electron microscopy (SEM), transmission electron microscopy (TEM), and electrochemical tests demonstrated that the NFL-7F sample exhibited the best OER performance, including superior stability and activity, compared to other samples. The results indicate that NH₄F plays a crucial role in optimizing the electronic structure and morphology of NiFe-LDHs, thereby facilitating enhanced OER kinetics. This study provides valuable insights into the structure–performance relationship of NiFe-LDH catalysts and highlights the importance of tuning the oxidation states of metal cations for the development of efficient electrocatalysts.