Boosting the OER via the metal–support interaction and H-bond network: amorphous RuOx on fluorinated Ruddlesden–Popper perovskites

Abstract

The oxygen evolution reaction (OER) is central to water electrolysis for green hydrogen production, where the development of efficient, stable, and cost-effective catalysts remains a key challenge. Ruthenium (Ru)-based catalysts are highly promising for OER, yet their practical deployment is limited by poor stability and low atomic utilization. Here, we report a fluorination-assisted loading strategy to fabricate an amorphous@crystalline composite catalyst, in which amorphous RuO_x active species are anchored onto a fluorine-modified Ruddlesden–Popper (R-P) perovskite support (La_1.2Sr_0.8Ni_0.6Fe_0.4O_4+δF_y) to form the catalyst denoted as RuO_x@LSNF-F. Fluorination induces robust metal–support interactions via electronegativity differences, stabilizing Ru⁴⁺ to balance the activity and stability while constructing an ordered hydrogen-bond network and optimizing the surface wettability. Electrochemical tests in 1.0 M KOH confirm the exceptional OER performance of RuO_x@LSNF-F, which achieves an overpotential of 287 mV at 10 mA cm⁻², a Tafel slope of 75 mV dec⁻¹, and a double-layer capacitance of 3.7 mF cm⁻² while maintaining stable operation for over 100 h, outperforming its non-fluorinated counterpart, the pristine support, and other benchmark Ru-based catalysts. Mechanistic studies reveal that the exceptional performance arises from the synergistic coupling of the adsorbate evolution mechanism (AEM) and lattice oxygen mechanism (LOM), enabled by the fluorination-engineered interface, while a hydrogen bond network is enhanced on the amorphous RuO_x layer to accelerate deprotonation and improve the surface wettability. This work presents a strategy for designing high-performance perovskite-based OER catalysts and advances the understanding of their structure–activity relationships.