NiFe-Layered Double Hydroxides Nanosheets Coordinated with Terephthalic Acid: Preferentially Adsorbing OH ^– but Repelling Cl ^– during Alkaline Seawater Oxidation

When NiFe-LDH is used as an oxygen evolution reaction (OER) catalyst for alkaline seawater electrolysis, the performance still suffers from slow catalytic kinetics and poor long-term stability. Inspired by the hard–soft-acid–base concept, herein, terephthalic acid (TPA) molecules are anchored on the surface of a NiFe-layered double hydroxide in situ grown on Ni foam (TPA-NiFe-LDH/NF) through coordination bonds, thus creating harder acidic Ni and Fe sites, preferentially adsorbing hard base OH– over soft base Cl–. Comprehensive characterizations indicate that the C–O–M bonds through metal-carboxylate coordination can stabilize the metal centers, suppress the metal dissolution, and accelerate catalytic OER kinetics. As a result, the modified sample demonstrates improved OER performance. Specifically, TPA-NiFe-LDH/NF exhibits lower overpotentials than NiFe-LDH/NF in the electrolytes of 1 M KOH, 1 M KOH + 0.5 M NaCl, and 1 M KOH + seawater. TPA-NiFe-LDH/NF also possesses much better long-term stability with stable operation even in alkaline seawater at 400 mA cm–2 for 560 h than NiFe-LDH/NF (less than 60 h). The anion exchange membrane electrolyzer of (+)TPA-NiFe-LDH/NF||MoNiP(−) delivers a high current density of 500 mA cm–2 at a cell voltage of 1.65 V for industrial alkaline simulated seawater splitting (6 M KOH + 0.5 M NaCl at 80 °C) and robust durability with stable operation over 110 h at 250 mA cm–2 for alkaline simulated seawater splitting (1 M KOH + 0.5 M NaCl at 25 °C). This study offers a new strategy to fabricate high-performance electrocatalysts for seawater oxidation.