In situ fabrication of S-type BiOI x Br y heterojunction with metallic Bi for boosting photocatalytic activity for CO2 reduction

Heterojunction construction and morphology control have always been considered effective ways to promote the capability of photocatalysts. In this work, BiOIxBry, S-type heterojunction photocatalysts with metallic Bi nanoparticles, were synthesizedin situusing a solvothermal method, and the influence of reaction temperature (180 °C-220 °C) and dopant doping amount on the catalysts' microscopic morphology, structure, and catalytic properties were researched. Study results revealed the 1:1 BiOIxBrysynthesized at 200 °C exhibited the optimum behavior in CO2reduction. Its catalytic CO2reduction to CH3OH was 932.88μmol gcat-1and C2H5OH was 324.46μmol gcat-1under the analog light source for 8 h, which was approximately 1.92 and 1.49 times higher than that of BiOI-200 °C, respectively. The reinforced catalytic properties are probably attributed to the synergistic effect between metallic Bi nanoparticles and BiOIxBryheterojunction. Thanks to the SPR effect ofin situmetallic Bi, the catalysts' photocarrier separation efficiency is facilitated. Additionally, the heterojunction formation contributes to that trend and more importantly, preserves the charge carriers with strong redox capacity in BiOIxBry, proving product selectivity. We also present a potential electron transfer mechanism involved in the BiOIxBryphotocatalytic CO2reduction based on the characterization analysis and experimental results.