Macroscopic Spontaneous Polarization and Surface Oxygen Vacancies Collaboratively Boosting CO Photoreduction on BiOIO Single Crystals.

Prompt recombination of photogenerated electrons and holes in bulk and on the surface of photocatalysts harshly impedes the photocatalytic efficiency. However, the simultaneous manipulation of photocharges in the two locations is challenging. Herein, the synchronous promotion of bulk and surface separation of photoinduced charges for prominent CO photoreduction by coupling macroscopic spontaneous polarization and surface oxygen vacancies (OVs) of BiOIO single crystals is reported. The oriented growth of BiOIO single-crystal nanostrips along the [001] direction, ensuing substantial well-aligned IO polar units, renders a large enhancement for the macroscopic polarization electric field, which is capable of driving the rapid separation and migration of charges from bulk to surface. Meanwhile the introduction of surface OVs establishes a local electric field for charge migration to catalytic sites on the surface of BiOIO nanostrips. Highly polarized BiOIO nanostrips with ample OVs demonstrate outstanding CO reduction activity for CO production with a rate of 17.33 µmol g h (approximately ten times enhancement) without any sacrificial agents or cocatalysts, being one of the best CO reduction photocatalysts in the gas-solid system reported so far. This work provides an integrated solution to governing charge movement behavior on the basis of collaborative polarization from bulk and surface.