Triggering Overall Crystal Polarization by Octahedron Elongation Distortion for Highly Boosted and Selective Aerobic Photo-Oxidation

Abstract

High carrier recombination causes a huge waste of photogenic charge, which severely restrains the photocatalytic efficiency. Creating polarization electric field by polar photocatalytic materials proves effective to promote charge separation, while developing efficient polarization strategy is challenging and the related micromechanism remains obscure. Here, overall polarization is achieved in Bi₂MoO₆ single crystal photocatalyst by lateral growth of the nanoplate along {010} facets. Gradual elongation of equatorial Mo─O bonds along the MoO₆ octahedral layer occurs, while the length of apical Mo─O bonds basically remains unchanged, thus allowing the large asymmetric distortion of MoO₆ octahedron for producing the microscopic polarization. Meanwhile, the lateral growth of Bi₂MoO₆ nanoplates enables the accumulation of distorted polar units, further increasing the polarization intensities. The inside-out crystal polarization significantly promotes the separation and migration of photogenerated charge carriers. The finely polarized Bi₂MoO₆ nanoplates exhibit an exceptional photocatalytic selective oxidation rate of benzyl alcohol (BA) to benzaldehyde (BAD) under visible light irradiation (Conversion (Con.) ≈100% within 30 min, Selectivity (Sel.) ≥95%), over 70.7 times that of original Bi₂MoO₆ nanosheets, on the condition of comparable O₂ adsorption capability. This study advances atomic-level mechanistic insight into polarized materials toward precise design of high-performance photocatalysts.