Iron (III)-Facilitated reconstruction in NiMn layered double hydroxides for initiating rapid oxygen evolution reaction

Abstract

Layered double hydroxides (LDHs) are emerging as efficient oxygen evolution reaction (OER) electrocatalysts due to their structural advantages and compositional flexibility. Despite their promise, Mn-based LDHs are hampered by poor conductivity, limiting their OER efficacy. This research introduces a hydrothermal and chemical etching technique to fabricate NF/NiMn LDH@NiMnFe(OH)_x structures, significantly improving OER performance. The study reveals that integrating Fe³⁺ into the NiMn LDH fosters a synergistic Ni–Fe interaction, markedly boosting electrocatalytic efficiency. The NF/NiMn LDH@NiMnFe(OH)_x-90 shows a low overpotential of 250 mV at 10 mA cm⁻² and a Tafel slope of 49.9 mV dec⁻¹ in 1 M KOH, surpassing both its NM precursor and other Ni-based LDH catalysts, including commercial RuO₂. In situ, Raman spectroscopy indicates a pivotal phase transition in NF/NiMn LDH@NiMnFe(OH)_x to NiOOH at elevated potentials, essential for OER activity. Raman peaks at 463 and 585 cm⁻¹ confirm this structural evolution. The OER activity boost is attributed to increased oxygen vacancies and enhanced conductivity. Moreover, NF/NiMn LDH@NiMnFe(OH)_x-90 maintains stability with negligible degradation after 24 h, underscoring its durability. These findings offer a strategic approach to designing high-performance OER electrocatalysts, leveraging nickel-based layered double-metal oxides for potential water-splitting applications, and emphasize the significance of surface engineering and compositional tuning.