Chiral (BiO)2CO3 Catalysts with Spin-Selective Charge Transport Enhance Photocatalytic Oxygen Evolution

Abstract

Photocatalytic water splitting to produce hydrogen is an essential pathway for clean energy conversion. Yet, its efficiency is limited by the sluggish kinetics of the oxygen evolution reaction (OER) and the rapid recombination of photogenerated charge carriers. The reaction requires the formation of O2 in its triplet ground state, and its pathway is closely related to the spin states of the intermediates. The need for spin matching introduces a significant kinetic barrier and may trigger a competitive two-electron side reaction that produces H2O2, thereby reducing the overall efficiency. The chiral-induced spin selectivity (CISS) effect can polarize electron spins without an external magnetic field, providing a new mechanism for controlling this multi-electron reaction pathway. Here we report, for the first time, the synthesis of intrinsically chiral bismuth subcarbonate ((BiO)2CO3, BOC) photocatalysts using sucrose as a chiral directing agent. The resulting chiral BOC materials exhibit hierarchical chirality, spanning from atomic-scale lattice distortion to macroscopic helical nanoarchitectures. Magnetic conductive atomic force microscopy (mc-AFM) measurements indicate that these chiral BOC materials act as spin filters and effectively polarize photogenerated carriers; the spin polarization (P) correlates positively with the optical chirality factor (g factor), reaching 68.3% in the sample with the strongest chirality. In photocatalytic oxygen evolution tests, the strongly chiral sample shows higher photocurrent density and faster reaction kinetics while significantly suppressing H2O2 byproduct formation. This study not only pioneers the extension of the CISS effect to carbonate-based photocatalytic systems, confirming its universality, but also establishes a new research paradigm for efficient photocatalytic oxygen evolution using BOC materials. Furthermore, these results systematically reveal an intrinsic relationship that chiral structure leads to spin polarization, which in turn improves catalytic performance, offering pivotal insights for the design of novel spin-controlled high-performance catalysts.