A field-programmable S-scheme heterojunction enabled by spin-polarized electron highway for solar hydrogen generation

Abstract

The inability to dynamically control charge-transfer pathways represents a fundamental limitation in advancing photocatalytic efficiency. Herein, we propose a “field-material co-design” paradigm to create a programmable weakly ferromagnetic S-scheme heterojunction, where incorporating ~10 nm α-Fe2O3 nanoparticles (exhibiting distinct weak ferromagnetism absent in bulk) is crucial for magnetic responsiveness. Under a 108 mT field, this hybrid achieves an exceptional H2 evolution rate of 9.3 mmol·h⁻¹·g⁻¹—a 33 % enhancement—and an apparent quantum efficiency of 13.2 % at 420 nm. This study presents the first systematic investigation of magnetic field effects in an S-scheme architecture. In situ and time-resolved spectroscopies unveil that the field promotes spin-polarized electron generation in α-Fe2O3, which synergistically couples with the S-scheme to enhance charge exhaustion and prolong carrier lifetimes. DFT calculations reveal spin-down Fe³⁺ 3d and O²⁻ 2p orbitals dominate near the Fermi level, creating a highly conductive “spin highway”, visually confirmed by multiphysics simulations showing a 3.6-fold enhanced interfacial field. This work establishes a proactive co-design strategy for dynamically tunable catalytic systems and opens a new avenue for the precision engineering of solar energy conversion devices.