Ferromagnetic Synergy in a Ruthenium Single-Atom Catalyst on NiCo ₂ S ₄ for Magnetically Enhanced Water Splitting

Atomic modulation in single-atom catalysts (SACs) can induce ferromagnetic properties by tuning the local electronic structure, driving significant enhancements in electrocatalytic water splitting. The induced ferromagnetism, coupled with modified electronic characteristics, promotes a spin-polarized pathway for efficient hydrogen and oxygen production. Leveraging this principle, Ru 1 NCS SAC was synthesized by anchoring ruthenium (Ru) onto paramagnetic NiCo 2 S 4 (NCS). Such a combination yielded significant improvements in electronic properties with induced ferromagnetic behavior, as confirmed through experimental analyses and atomistic simulations based on the spin-polarized density functional theory (DFT). The practical implications of these magneto-electronic enhancements were evident under an applied magnetic field of 240 mT, yielding overpotentials (η 10 ) of 49 mV for the hydrogen evolution reaction (HER) and 173 mV for the oxygen evolution reaction (OER). While Ru 1 NCS exhibited improved catalytic performance, surpassing traditional Pt/C and RuO 2 catalysts in mass activity and turnover frequency (TOF), applying an auxiliary magnetic field further enhanced the water-splitting efficiency by reducing cell voltage from 1.53 to 1.48 V. A comprehensive mechanistic understanding of the spin-dependent catalytic enhancement was established through combined experimental and theoretical analyses, while the role of ferromagnetic behavior in sustaining catalytic activity and stability was validated through time-dependent magneto-electrocatalysis. Together, these findings underscore the pivotal role of atomic modulation in enhancing magnetoresponsive behavior, providing an effective strategy to overcome kinetic limitations in the overall water-splitting reaction.