Tannic acid salt-modified CoFe-layered double hydroxide boosts stable seawater oxidation at an industrial-level current density†

Abstract

Seawater electrolysis for green hydrogen production is a promising approach toward achieving carbon neutrality. However, the abundance of Cl⁻ in seawater can severely corrode catalytic sites, significantly reducing the lifespan of seawater electrolysis systems. Herein, we present metal ion-chelated tannic acid nanoparticles anchored on the CoFe layered double hydroxide nanosheet array on nickel foam (CoFe LDH@CoFe-TA/NF), synthesized via an interfacial coordination assembly method, serving as an efficient and stable electrocatalyst for alkaline seawater oxidation (ASO). The formed CoFe-TA nanoparticles promote the transformation of Co³⁺ into the more robust acid Co⁴⁺, thereby favoring the adsorption of the hard base OH⁻ rather than the soft base Cl⁻. In addition, the CoFe-TA ligand network effectively inhibits metal ion leaching and stabilizes active sites. As a result, the CoFe LDH@CoFe-TA/NF electrode requires a low overpotential of only 379 mV to obtain a current density of 1000 mA cm⁻² in 1 M KOH + seawater. Furthermore, the electrode also shows a stable operation for 450 h at an industrial-level current density, underscoring its potential for sustainable energy applications.