Unveiling rare ionic bonds in dissimilar 2D materials for selective ampere-level oxygen evolution reaction in seawater

Abstract

Direct electrocatalytic seawater splitting is a potential sustainable solution for large-scale green hydrogen production. However, anode deactivation due to impurities and unwanted reactions in seawater hinders its long-term performance. Here, we present a stable ionically bonded metal–organic framework/iron oxide (MOF/Fe₂O₃) heterostructured catalyst constructed via solid–liquid interfacial chemistry at room temperature. The unique M–O–M (M = metal) ionic bonds at the two-dimensional interface enhance the individual material properties, introducing additional active sites and creating facile charge flow. Theoretical calculations reveal that this system favours hydroxyl ion adsorption and inhibits the chlorine reaction, preventing corrosion and making the catalyst functional for over 900 h in complex seawater. It achieves a current density of 1 A cm⁻² at an overpotential of 410 mV, which is ∼200% higher than that of commercially used IrO₂. The heterostructured catalyst demonstrated durable performance at a higher current density of ∼1.5 A cm⁻² for more than 350 h due to selective anodic reaction and anti-corrosive behaviour against chlorine corrosion. This study provides a scalable strategy to modify the chemical states at heterointerfaces to develop robust catalysts for large-scale direct seawater splitting.