Identification of intrinsic vacancies and polarization effect on ternary halo‐sulfur‐bismuth compounds for efficient CO2 photoreduction under near‐infrared light irradiation

Abstract

AbstractTernary halo‐sulfur bismuth compound Bi19X3S27 (X = Cl, Br, I) with distinct electronic structure and full‐spectrum light‐harvesting properties show great application potential in the CO2 photoreduction field. However, the relationship between photocatalytic CO2 reduction performance and the function of halogens in Bi19X3S27 is still poorly understood. Herein, a series of Bi19X3S27 nanorod photocatalysts with intrinsic X and S dual vacancies were developed, which showed significant near‐infrared (NIR) light responses. The types and concentrations of intrinsic vacancies were confirmed and quantified by positron annihilation spectrometry and electron spin resonance spectroscopy. Experimental results showed that Br atoms and intrinsic vacancies (dual Br‐S) in Bi19Br3S27 could greatly enhance the internal polarized electric field and improve the transfer and separation of photogenerated carriers compared with Bi19Cl3S27 and Bi19I3S27. Theoretical calculations revealed that Br atoms in Bi19Br3S27 could facilitate CO2 adsorption and activation and decrease the formation energy of reactive hydrogen. Among Bi19X3S27 nanorods, Bi19Br3S27 nanorods revealed the highest CO2 photoreduction activity with CO yield rate of 28.68 and 2.28 μmol gcatalyst−1 h−1 with full‐spectrum and NIR lights, respectively. This work presents an atomic understanding of the intrinsic vacancies and halogen‐mediated CO2 photoreduction mechanism.