Phosphate-functionalized amorphous NiMoO4 nano-armor on hematite: Robust ligand-anchoring engineering for efficient corrosion-resistant seawater splitting

Photoelectrochemical seawater splitting is promising for renewable hydrogen, yet severe chloride corrosion remains a roadblock. Although amorphous catalysts improve hematite ( α -Fe 2 O 3 ) photoanode activity, their defect-enabled functionality inherently accelerates structural degradation, exacerbating chloride-induced corrosion. Here, a synergistic dual-functional nano-armor is designed by anchoring phosphate (PO 4 3− ) to active sites on amorphous NiMoO 4 (a-NiMoO 4 @PO 4 3− ), achieving dual activity-stability enhancement. Detailed physicochemical characterization and density functional theory (DFT) calculations show that the successful and stable anchoring of phosphate is highly dependent on the amorphous structural properties of a-NiMoO 4 . Its rich disordered coordination environment provides sufficient highly reactive sites, allowing PO 4 3− to be firmly bound through strong coordination bonds, which is the key for the dual role of PO 4 3− coordination. As a dynamic Cl − shield, PO 4 3− coordinates unsaturated Ni sites, forming an anionic layer that resists Cl − via steric-electrostatic blocking. As an electronic modulator, PO 4 3− triggers metal-to-ligand charge transfer at Ni sites, depleting electron density to optimize the intermediate adsorption of oxygen evolution reaction (OER) and reduce kinetic barriers. Simultaneously, this charge redistribution induces a built-in electric field that accelerates hole-selective transport. Benefiting from these dual effects, the Fe 2 O 3 /a-NiMoO 4 @PO 4 3− achieves 4 mA cm −2 at 1.23 V RHE with exceptional stability in seawater. This work leverages the unique coordination flexibility of amorphous structures to construct a phosphate-coordinated bifunctional nano-armor on hematite photoanodes, which simultaneously enables efficient chloride exclusion and electronic structure optimization. The synergistic mechanism, rooted in strong phosphate anchoring on amorphous carriers, establishes a new design paradigm for photoelectrochemical systems that integrate high activity with extreme environmental stability, providing an efficient pathway toward corrosion-resistant seawater splitting.