Phosphate-Modulated Heterojunction to Trigger the Lattice Oxygen Mechanism for Industrial-Scale Water Electrolysis

To address the issue of slow kinetics in the oxygen evolution reaction (OER) during industrial hydrogen evolution, phosphate adsorption or intercalation is commonly employed to modulate the electronic structure of electrocatalysts. However, these binding modes suffer from weak interfacial attachment and limited electronic coupling, leading to gradual phosphate leaching under operating potentials and a loss of structural stability in the material. Here we report a surface chemical anchoring strategy that grafts phosphate groups directly onto a Ni–Mo-based heterojunction catalyst (Pi-NiO/Ni/MoO3) via P–O–Ni bonds. The chemically bonded phosphate, synergizing with interfacial charge transfer across the heterojunction, raises the Ni valence state and strengthens metal–oxygen covalency, enhancing stability and lowering the potential required for dynamic surface reconstruction into highly active NiOOH. A series of in situ spectroscopic measurements, differential electrochemical mass spectrometry (DEMS), and density functional theory (DFT) reveal that phosphate modulation shifts the dominant OER pathway from the adsorbate evolution mechanism (AEM) to the lattice oxygen mechanism (LOM), with the 18O/16O ratio establishing a marked increase of 2.03 times. Consequently, Pi-NiO/Ni/MoO3 achieves an industrial-level current density of 500 mA·cm–2 at an overpotential of 359 mV in 1 M KOH and maintains stable operation for over 2250 h. When employed in an anion exchange membrane water electrolyzer (AEMWE), it delivers 1 A·cm–2 at a low cell voltage of only 1.68 V, outperforming most of reported state-of-the-art electrocatalysts. This work lays a solid foundation for the rational design of durable electrocatalysts toward sustainable industrial-scale hydrogen production.