Synergy of Homojunction/Heterojunction to Enforce Photocatalytic Performance of BiSI/TiO₂ Quantum Dots/TiO_2–<i>x</i> Nanocomposites in NH₃ Generation

The development of the global economy has caused irreparable damage to energy resources and the environment. Therefore, it is essential to find a solution to effectively deal with the energy crisis and environmental pollution. Photocatalytic nitrogen fixation processes employ renewable solar energy and water molecules under mild conditions to produce ammonia. In this attempt, in searching for efficacious materials for this reaction, ternary BiSI/TiO2 quantum dots (QDs)/TiO2–x nanocomposites were designed and fabricated by a green and easy procedure. The amount of ammonia generation over the optimal ternary BiSI/TiO2 QDs/TiO2–x photocatalyst reached 20,904 μmol L–1 g–1 within 180 min under ambient temperature and pressure, which was about 7.78, 5.45, 1.75, and 3.09 times as high as TiO2 QDs, TiO2–x, TiO2 QDs/TiO2–x, and BiSI photocatalysts, respectively. The matching of the energy bands with the developed double S-scheme homojunction/heterojunction mechanism and the establishment of optimal contact area between the components facilitated the separation and migration of charges and led to outstanding photocatalytic ability in ammonia generation. Furthermore, the improved specific surface area due to the quantum particle size and oxygen deficiency provided many active centers for adsorption and activation of dinitrogen molecules. As a result, the BiSI/TiO2 QDs/TiO2–x nanocomposites with biocompatible elements and remarkable stability are suitable for employing in the field of solar energy conversion.