Spin-Polarized Electron Transport Promotes the Oxygen Reduction Reaction

Oxygen evolution (OER) and oxygen reduction (ORR) reactions are central to the efficiency of electrolysis and fuel cells, involving the paramagnetic triplet ground state of oxygen and the singlet ground state of water. Here, we demonstrate that spin-polarized currents enhance the ORR activity. Using a silver-coated nickel electrode over a neodymium (Nd) magnet, we observed that ORR performance is maximized when the Ag layer is thinner than the spin diffusion length of silver─conditions under which spin alignment at the electrode-electrolyte interface is maintained. In contrast, experiments with thicker Ag layers lead to spin relaxation and diminished electrocatalytic activity. A model description of this system shows that a substantial spin polarization at the interface is accompanied by a large two-electron transfer, which satisfies conservation of angular momentum during ORR. These findings highlight the critical role of spin-selective charge transfer and offer insights into the control of reaction pathways in oxygen electrocatalysis.