Magnetic-Field-Induced Spin Transition in Single-Atom Catalysts for Nitrate Electrolysis to Ammonia

Electrochemical nitrate reduction (NitRR) using single-atom catalysts (SACs) offers a promising pathway for sustainable ammonia production. Herein, we explore the use of external magnetic fields to regulate the spin state of Ru SACs supported on nitrogen-doped carbon (Ru-N-C), aiming to optimize their catalytic performance toward NitRR. Under magnetic field conditions, Ru-N-C exhibits a remarkable NH₃ yield rate of ∼38 mg L^-1 h^-1 and a Faradaic efficiency of ∼95% over 200 h. Our spectroscopic and magnetic characterization demonstrates that the external magnetic field induces a spin transition to a high-spin state in Ru SACs/N-C. Theoretical analysis further suggests that the increased spin state of Ru shifts the density of states away from the Fermi level, weakening the adsorption affinity for *NH₂. Economic analysis hints at cost effectiveness and scalability. Overall, this study demonstrates that magnetic-field-induced spin modulation effectively optimizes NitRR electrocatalysts.