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

Abstract Heterojunction construction and morphology control have always been considered effective ways to promote the capability of photocatalysts. In this work, BiOI x Br y , S-type heterojunction photocatalysts with metallic Bi nanoparticles, were synthesized in situ using 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 x Br y synthesized at 200 °C exhibited the optimum behavior in CO 2 reduction. Its catalytic CO 2 reduction to CH 3 OH was 932.88 μ mol g cat −1 and C 2 H 5 OH was 324.46 μ mol g cat −1 under 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 x Br y heterojunction. Thanks to the SPR effect of in situ metallic 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 x Br y , proving product selectivity. We also present a potential electron transfer mechanism involved in the BiOI x Br y photocatalytic CO 2 reduction based on the characterization analysis and experimental results.