In‐Plane Creation of Rare Earth‐Induced Spin Filtering Effect in Ultrathin Nanosheets for Enhanced Water Oxidation

Abstract Beyond the common charge property, spin regulation is also critical to improve the oxygen evolution reaction (OER) catalysis that involves electron spin‐related conversion from singlet OH − /H 2 O to triplet O 2 . Rare earth (RE) elements show great potential for spin‐magnetic tuning due to their rich unpaired 4f electron and tunable spin‐orbit coupling, but they still lack well‐defined typical models for systematic spin investigation. Herein, a spin‐magnetic regulating strategy is defined based on in‐plane creation of atomic‐disperse RE‐doped ultrathin nanosheets (UNSs), via coupling Gd 3+ dopants with adjacent Ni/O vacancies to create bounded magnetic polarons (BMPs) within the ultrathin nano‐regime. The overlapped BMPs generate unique short‐range spin exchange and long‐range ferromagnetic ordering, enhancing the spin polarization of active sites. Thereby, they represent an efficient and robust “spin filter” that promotes consistent spin‐selective electron extraction/transfer during the electrochemical reconstruction‐involved OER process. Furthermore, the Gd‐doped UNSs serve as spin‐filtering support for anchoring RuO 2 , achieving high activity with ultralow overpotential of 208.4 mV at 100 mA cm −2 and long‐term stability over 100 h in an anion exchange membrane water electrolyzer, superior to most state‐of‐the‐art catalysts.