Dynamic Reconstruction of Crystal/Amorphous Hetero‐Phosphate Janus Interfaces for Highly Stable Seawater Splitting

Abstract The abundant seawater resources provide favorable advantages for the large‐scale application of seawater electrolysis to produce hydrogen. However, the catalysts are prone to triggering the chlorine evolution reaction (CER) and are easily corroded by Cl ⁻ , which are key challenges that need urgent resolution in seawater electrolysis technology. Here, a crystal/amorphous heterostructure bifunctional composite catalyst (caMo‐NiFePO/NMF) for seawater splitting is synthesized through in situ etching and phosphorylation. The incorporation of Mo facilitates the formation of crystalline‐amorphous interfaces and adjusts the Fe electronic states and d‐band centers, thereby boosting the adsorption capacity of ^* OOH intermediates and the repulsion of Cl ⁻ , forming a dynamic ^* OOH‐rich, Cl ⁻ ‐poor Janus interface. This enhances catalytic activity and prevents catalyst deep reconstruction toward hydroxyl metal oxide, leading to highly stable and effective seawater splitting. Noteworthy, the caMo‐NiFePO/NMF requires a low overpotential of 328 mV to reach 500 mA cm ⁻² in alkaline seawater for oxygen evolution reaction (OER), avoiding triggering CER. It also shows excellent activity with 327 mV to 500 mA cm ⁻² in alkaline seawater for hydrogen evolution reaction (HER). As a bifunctional catalyst, caMo‐NiFePO/NMF demonstrates excellent performance with a cell potential of 1.7 V to achieve 100 mA cm ⁻² in alkaline seawater, maintaining remarkable stability over 1000 h.