Z-scheme g-C₃N₄/Bi₂O₂[BO₂(OH)] heterojunction for enhanced photocatalytic CO₂ reduction

Construction of Z-scheme heterojunction photocatalyst for CO₂ photoreduction shows great significance as it holds strong redox ability and high charge separation efficiency. In this work, we developed a Z-scheme heterojunction photocatalyst graphitic carbon nitride (g-C₃N₄)/basic bismuth borate (Bi₂O₂[BO₂(OH)]) by a simple high-energy ball milling method. The structure, surface element distribution and morphology of the composite samples were systematically analyzed. The photocatalytic performance of the samples was surveyed by CO₂ reduction experiment under the simulated solar light irradiation. Almost all the g-C₃N₄/Bi₂O₂[BO₂(OH)] composites show enhanced photocatalytic activity for converting CO₂ into CO, and the highest CO production rate observed for g-C₃N₄/Bi₂O₂[BO₂(OH)] (CNBB-3) among all the samples was determined to be approximately 6.09 µmol g^-1 h^-1, which is 2.78 times higher that of pristine g-C₃N₄. The largely strengthened photocatalytic CO₂ reduction activity mainly originates from the formation of Z-scheme band structures between g-C₃N₄ and Bi₂O₂[BO₂(OH)] benefiting for the efficient charge separation, which was confirmed by the photoeletrochemical, photoluminescence and ESR spectra. This study provides a new reference for fabrication of high-performance Z-scheme photocatalysts for CO₂ reduction.