Rare-earth carbonate hydroxide regulated FeCoNi-layered double hydroxides heterostructures: enhanced proton desorption and chloride corrosion tolerance for alkaline water/seawater oxidation

Transition-metal-based layered double hydroxides (LDHs) are attractive yet challenging catalysts for the alkaline oxygen evolution reaction (OER). To advance their practical applications in overall water splitting, substantial enhancements in both activity and, more critically, long-term stability are imperative. Herein, we develop a heterostructured catalyst, comprising Fe-Co-Ni LDH and lanthanum(praseodymium) carbonate hydroxide grown on nickel foam (FCN-LDH/LPCH@NF), which demonstrates significantly enhanced OER activity and durability in both alkaline freshwater and seawater. The strong interfacial electronic coupling within the FCN-LDH/LPCH heterostructure leads to an 8.7-fold increase in electrocatalytic current density at an overpotential of 250 mV compared to the FCN-LDH@NF, achieving a low overpotential of 194 mV at 10 mA cm⁻² in freshwater. Comprehensive experimental and theoretical analyses reveal that such coupling promotes the deprotonation of the FCN-LDH and the key reaction intermediates during the OER, thereby accelerating the OER kinetics, while simultaneously reinforcing the structural stability against chemical and chloride corrosion. This work elucidates the critical link between deprotonation capability and OER activity, offering a generalizable design principle for developing robust electrocatalysts. More impressively, the FCN-LDH/LPCH@NF exhibits great potential for overall water/seawater splitting in anion exchange membrane electrolyzers, maintaining stable performance at 1.5 A cm⁻² for >1000 h.