Orbital overlap-stabilized amorphous metal phosphate frameworks for industrial current density electrocatalysis

Abstract

Transition-metal phosphates are promising catalysts for water splitting owing to their high density of active sites and open framework that facilitates rapid ion diffusion. However, lattice-oxygen-induced phosphate leaching and the weak, variable M–O covalency often lead to surface reconstruction and performance degradation at high current densities. Here, we address these challenges by constructing an amorphous phosphate surface layer (Ru2-De) through a minor Ru alloying strategy combined with in situ amorphization of an FeCoNiRuP precursor. The incorporation of Ru induces strong Ru 4d–O 2p hybridization, which enhances orbital overlap and M–O covalency, effectively suppressing phosphate framework dissolution. Simultaneously, the increased density of states near the Fermi level and narrowed band gap improve charge transport. As a result, Ru2-De exhibits excellent catalytic activity with overpotentials of 23 mV for the hydrogen evolution reaction (HER) and 257 mV for the oxygen evolution reaction (OER) at 10 mA cm⁻². Notably, when employed simultaneously as both the cathode and anode in an anion-exchange membrane (AEM) electrolyzer at 80 °C, the system exhibits high efficiency, requiring only 1.61 V to reach 500 mA cm⁻², while retaining exceptional durability for over 100 h at 1 A cm⁻². These metrics place Ru2-De among benchmark catalysts for high-current-density water electrolysis. Such a low-Ru, scalable platform provides an effective strategy to suppress structural collapse and active-site degradation at high current densities, offering a robust pathway toward industrially durable water electrolysis.