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, Ru1NCS SAC was synthesized by anchoring ruthenium (Ru) onto paramagnetic NiCo2S4 (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 (η10) of 49 mV for the hydrogen evolution reaction (HER) and 173 mV for the oxygen evolution reaction (OER). While Ru1NCS exhibited improved catalytic performance, surpassing traditional Pt/C and RuO2 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.