Abstract
The use of photocatalytic CO(2) reduction as a green technology has attracted the attention of scholars. Nevertheless, the lower visible-light utilisation and photocatalytic efficiency of catalysts remain a challenge. In this work, Bi(x)O(y)Br(z) photocatalysts were synthesised using a hydrothermal method by adjusting the molar ratio of Bi(NO(3))(3)·5H(2)O and C(19)H(42)BrN (Bi:Br ratio) and the pH value of the precursor solution. The obtained samples were characterised, and the CO(2) reduction performance was tested. The results showed that the phase composition for most of the samples was Bi(4)O(5)Br(2), and BiOBr or Bi(5)O(7)Br was also confirmed in a small number of samples. Owing to the effects of pH and the Bi:Br ratio on the reaction process, BiOBr→Bi(4)O(5)Br(2)→Bi(5)O(7)Br transformation occurred. Acidic conditions are conducive to the formation of BiOBr. In alkaline environments, bismuth-rich Bi(4)O(5)Br(2) or even Bi(5)O(7)Br easily forms. Bi(4)O(5)Br(2) has self-assembled microsphere and irregular polyhedron morphologies. The polyhedron Bi(4)O(5)Br(2) results in CO and CH(4) yields of 10.34 μmol·g(-1)·h(-1) and 1.86 μmol·g(-1)·h(-1) in CO(2) reduction, respectively. Although the microsphere Bi(4)O(5)Br(2) has a maximum light absorption wavelength of 438 nm, the polyhedron Bi(4)O(5)Br(2) has the best photocatalytic CO(2) reduction performance and CO selectivity. This work describes the controllable preparation of Bi(4)O(5)Br(2) at various pH values and Bi:Br ratios and the optimisation of its photocatalytic performance.