Enhancing hydrogen production from photocatalytic water splitting over ZnIn₂S₄/Ni-MOF via magnetically induced spin polarization

Photocatalytic water splitting (PWS) for hydrogen production is a highly promising technology to address energy and environmental challenges and enable efficient solar energy conversion and storage. However, in light-driven PWS systems, rapid recombination of photogenerated electron–hole pairs due to low charge separation efficiency leads to unsatisfactory catalytic performance. Recently, introducing a magnetic field into PWS has proven effective in enhancing photocatalytic activity by suppressing charge recombination. Notably, nickel ions in Ni-MOF can act as magnetic response centers. Building on this, we report a dramatically enhanced PWS system using a ZnIn₂S₄/nickel-based metal–organic framework (ZnIn₂S₄/Ni-MOF) ferromagnetic heterojunction photocatalyst under a static magnetic field. A series of ZnIn₂S₄/Ni-MOF catalysts with varied Ni-MOF content was synthesized; the optimized sample achieved a hydrogen evolution rate of 71.91 mmol·g⁻¹ ·h⁻¹ under a 500 mT static magnetic field, 2.97 times higher than under visible-light irradiation alone. Systematic photoelectrochemical, magnetic, and DFT studies revealed that this enhancement stems from significantly prolonged carrier lifetimes due to spin-polarization effects of Ni ions under the magnetic field. This work offers new insights into designing high-efficiency heterojunction photocatalysts leveraging electron spin polarization.