Chemical bond induced spin polarization towards optimized photocatalytic overall water splitting

Abstract

Photocatalytic overall water splitting (POWS), a sustainable route for solar-to-hydrogen conversion, faces challenges from rapid charge recombination and material instability. This study demonstrates a 12-fold enhancement in POWS by integrating spin polarization through platinum quantum dots chemically bonded to brookite/anatase TiO2. Advanced characterizations, including X-ray absorption spectroscopy and X-ray photoelectron spectroscopy, confirm Pt-Ti coordination (with a bond length of 2.84 Å) and electron transfer to Pt, thereby enriching the active sites. Magnetic circular dichroism spectroscopy reveals spin-polarized band structures in Pt/TiO2, which are absent in pristine TiO2, thereby suppressing charge recombination. Under light irradiation, Pt/TiO2 achieves H2 and O2 evolution rates of 310 and 150 µmol h−1 g−1, respectively, and an apparent quantum yield of 2.1 % at 365 nm. Density functional theory calculations trace this enhancement to optimized hydrogen adsorption free energy and reduced oxygen evolution overpotential. Spin-polarized Ti 3d and Pt 5d orbitals near the Fermi level extend carrier lifetimes, while a shifted d-band center facilitates oxygen desorption. This work establishes spin polarization engineering via cocatalysts as a transformative strategy for POWS, introducing a spin-dependent mechanism that addresses intrinsic limitations in photocatalysis, and offers a pathway to efficient solar fuel generation.

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