Ce(OH) ₃ /NiFe-PO Heterojunction with an Interfacial Hydrogen-Bond Network for Enhanced Seawater Splitting

Direct seawater splitting to produce hydrogen is widely recognized as a sustainable green technology; however, the sluggish kinetics of the oxygen evolution reaction (OER) and the high chloride ion (Cl–) concentration in seawater severely limit overall efficiency. Here, we develop a Ce(OH)3/NiFe-PO heterostructured electrocatalyst that simultaneously enhances the dynamic activity and durability for seawater splitting. The formation of a Ce(OH)3/NiFe-PO heterojunction induces interfacial electronic interactions, generating electron-deficient sites to rapidly reconstruct NiFeOOH catalytic sites for enhancing the OER activity. Meanwhile, it facilitates the formation of a hydrogen-bond network at the electrode–solution interface to significantly accelerate OH– transport for boosting the kinetics of the OER kinetics. As a result, the catalyst achieves 0.5 A cm–2 at an overpotential of only 284 mV in 1 M KOH with a low Tafel slope of 23.1 mV dec–1. In alkaline seawater, the catalyst reaches the same current density at an overpotential of 353 mV, effectively suppressing the chlorine evolution reaction. Furthermore, phosphate groups and the hydrogen-bond network on the catalyst surface effectively block the Cl– adsorption, enabling stable operation at 0.5 A cm–2 for at least 500 h with negligible current decay. The results highlight a heterojunction structure strategy that comprises high activity, selectivity, and corrosion resistance for practical seawater splitting applications.