One-step preparation of novel Bi-Bi2O3/CdWO4 Z-scheme heterojunctions with enhanced performance in photocatalytic NH3 synthesis

This study focuses on the design and synthesis of a novel ternary composite photocatalyst, Bi-Bi2O3/CdWO4, using a one-step solvothermal method. A comprehensive investigation was conducted to analyze the morphology, specific surface area, structure, optical property, and photoelectric chemical property of the composite. The incorporation of Bi-Bi2O3 was found to significantly impact the growth of CdWO4 crystals, resulting in a morphological transformation into nanoparticles. This morphological change has been shown to enhance the specific surface area of the catalyst, thereby improving its catalytic performance. Furthermore, the incorporation of Bi-Bi2O3 has been demonstrated to greatly enhance the light absorption capability of CdWO4, which also favored the photocatalytic N2 fixation (PNF) reaction. However, after conducting a comprehensive analysis of different Bi-BiO3/CdWO4 and two reference samples Bi/CdWO4 and Bi2O3/CdWO4, it was determined that the improvement of photogenerated charge carrier separation efficiency is the decisive factor determining the performance of the ternary composite catalyst. The closely bound Bi-Bi2O3 on the CdWO4 surface triggers the formation of a heterojunction structure at their interface. By analyzing the band structure of CdWO4 and Bi2O3, it is suggested that the heterojunction operates through a Z-scheme mechanism. The Bi metal serves as a bridge that intimately binds CdWO4 and Bi2O3, facilitating the rapid migration of electrons and improved charge separation. Therefore, the Bi-Bi2O3/CdWO4 composite exhibits high performance in PNF reactions. The optimal 7.5% Bi-Bi2O3/CdWO4 catalyst presents a PNF rate of 434.9 mu mol L-1 g-1 h-1 under simulated sunlight irradiation, which is 4.9 times that of pure CdWO4. These findings from this study may offer valuable insights into the design and synthesis of new photocatalysts for PNF.