Collaborative reconstruction of FeOOH/FeNiCo-LDH heterogeneous nanosheets for enhancing anion exchange membrane seawater electrolysis

Abstract

Transition-metal based layered double hydroxides (TM-LDHs) have attracted widespread attention due to their advantages for the electrocatalytic oxygen evolution reaction (OER). However, their sluggish and unstable reconstruction during the OER has seriously limited their applications in water electrolysis at industrial-level current density. Herein, FeOOH/FeNiCo-LDH heterogeneous nanosheets (2.1 nm in thickness) are uniformly integrated on honeycomb-channel N-doped carbon (FeOOH/FeNiCo-LDH/HCNC) through a self-sacrificing and dual-ion etching strategy. Thermodynamically favoured hydrogen/electron-capturing ability of FeOOH together with kinetically favoured rapid mass/electron transfer efficiency of conductive HCNC collaboratively accelerates the reconstruction of FeNiCo-LDH to generate highly active and stable FeNiCoOOH species, which displays an optimal reaction pathway with reduced energy barrier for the OER. Consequently, FeOOH/FeNiCo-LDH/HCNC exhibits superior OER activity in both alkaline freshwater (η₁₀ = 258 mV with Tafel slope of 32.4 mV dec⁻¹) and alkaline natural seawater (η₁₀ = 296 mV with Tafel slope of 54.7 mV dec⁻¹). When applied in anion exchange membrane electrolyzer as OER electrocatalyst, FeOOH/FeNiCo-LDH/HCNC achieves outstanding stability with low cell-voltage increase rates of 1.7 mV h⁻¹ (freshwater) and 1.5 mV h⁻¹ (seawater) over 120 h at the industrially required current density of 500 mA cm⁻². This study proposed an ingenious reconstruction strategy for advanced TM-LDH electrocatalysts toward industrial applications.