In situ fabrication of S-type BiOI x Br y heterojunction with metallic Bi for boosting photocatalytic activity for CO2reduction

Abstract

Heterojunction construction and morphology control have always been considered effective ways to promote the capability of photocatalysts. In this work, BiOI_xBr_y, 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 BiOI_xBr_ysynthesized at 200 °C exhibited the optimum behavior in CO₂reduction. Its catalytic CO₂reduction to CH₃OH was 932.88μmol g_cat^-1and C₂H₅OH was 324.46μmol g_cat^-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 BiOI_xBr_yheterojunction. 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 BiOI_xBr_y, proving product selectivity. We also present a potential electron transfer mechanism involved in the BiOI_xBr_yphotocatalytic CO₂reduction based on the characterization analysis and experimental results.

Keywords: BiOBr; BiOI; SPR; heterojunction; photocatalytic CO2 reduction.