Insight into crystal-structure dependent charge separation and photo-redox catalysis: A combined experimental and theoretical study on Bi(IO 3 ) 3 and BiOIO 3

Abstract Solar-driven conversion for CO 2 reduction and oxygen activation reactions show huge potentials for energetic and environmental applications. However, the influence of crystal structure of a photocatalyst on its photocatalytic performance has been seldom investigated so far. Herein, to probe the relationship between crystal structure and photocatalytic properties, two bismuth iodates, the centrosymmetric (CS) monoclinic Bi(IO 3 ) 3 and noncentrosymmetric (NCS) orthorhombic BiOIO 3 are employed as the models. The photocatalytic reduction and oxidation capabilities of Bi(IO 3 ) 3 and BiOIO 3 were surveyed by monitoring the CO 2 reduction and oxygen activation reactions. The results revealed that BiOIO 3 shows far superior photocatalytic activity than Bi(IO 3 ) 3 , which can more efficiently convert CO 2 into CO and produce larger amounts of O 2 − and OH. The experimental characterizations and DFT calculations co-uncovered that much more efficient charge separation and migration occur in BiOIO 3 in compared to Bi(IO 3 ) 3 , which are responsible for the obviously higher photoactivity of BiOIO 3 . This is mainly due to that the NCS crystal structure of BiOIO 3 that gives rise to a large macroscopic polarization, facilitating the separation of photogenerated electron-hole pairs. The microscopic first hyperpolarizability for BiOIO 3 was calculated to be 2.56 × 10 −30  esu for the dominant component at the static limit and 15.73 × 10 −30  esu at the wavelength 409.1 nm, which well verifies the strong polarization of BiOIO 3 . This study may furnish the perspective into designing high-performance photocatalytic materials on the basis of crystal structure engineering.