Collaborative reconstruction of FeOOH/FeNiCo-LDH heterogeneous nanosheets for enhancing anion exchange membrane seawater electrolysis
Abstract
Transition-metal based layered double hydroxides (TM-LDHs) has drawn widespread attention due to their advantages for electrocatalytic oxygen evolution reaction (OER). However, their sluggish and unstable reconstruction during OER has seriously limits their application 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. Take full advantage of rapid mass transfer effeciency from conductive HCNC, the hydrogen-affinitive and strong-electronegative FeOOH can well accelerate the surface reconstruction of FeNiCo-LDH to generate highly active and stable FeNiCoOOH. 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 industrially required current density of 500 mA cm-2. This study proposed an ingenious reconstruction strategy for advanced TM-LDHs electrocatalysts toward industrial applications.