Dipole moment regulation by Ni doping ultrathin Bi4O5Br2 for enhancing internal electric field toward efficient photocatalytic conversion of CO2 to CO

Abstract

The low efficiency of photogenerated carrier separation, and the poor adsorption and activation ability of CO₂ on the surface of photocatalyst were the key problems to limit the efficiency of photocatalytic CO₂ reduction. Hence, maximally accelerating the immigration of photogenerated charges d increasing the number of active sites are critical points to boost the overall performance of photocatalytic CO₂ reduction. However, it is still huge challenge. In this work, the Ni-doped ultrathin Bi₄O₅Br₂ nanosheets, which was successfully prepared by hydrothermal and ultrasonic chemical stripping methods, exhibited efficient photocatalytic conversion of CO₂ to CO. The results of experiments and theoretical calculations indicated that the doped Ni²⁺ significantly increased the crystal dipole moment of Bi₄O₅Br₂ in y direction (from 0 to 0.096 eÅ), which enhanced the polarized electric field strength inside Bi₄O₅Br₂, and further promoted the immigration of photogenerated carriers. Meanwhile, the ultrathin structure and doped Ni²⁺ synergistically increased the number of active sites, thereby promoting the adsorption and activation of CO₂ molecules, as evidenced by experimental and theoretical results collectively. As result, The CO yield was as high as 26.57 μmol g^–1 h^–1 for the prepared Ni-doped ultrathin Bi₄O₅Br₂ nanosheets under full spectrum light irradiation, which was 9.48 times that of Bi₄O₅Br₂. Therefore, it is of great scientific significance in this study to explore strategies to promote the separation of photogenerated carriers and enhance the adsorption and activation ability of CO₂ on the surface.