Oxygen vacancies in Bi2Sn2O7 quantum dots to trigger efficient photocatalytic nitrogen reduction

Constructing highly efficient ultra-small nanomaterials to achieve nitrogen reduction without sacrificing reagents or additional photosensitizers is still challenging. Herein, one-step solvothermal method was used to tune Bi2Sn2O7 to the quantum dots (QDs), so as to tune the active sites on the surface and achieve the optimization of the energy band structure. Benefiting from quantum size effect and electron back-donation mechanism of surface oxygen vacancies, the improved charge migration and optimized molecular nitrogen activation in Bi2Sn2O7 QDs can be achieved, triggering excellent photocatalytic nitrogen fixation behavior. The ammonia generation rate over Bi2Sn2O7 QDs is up to 334.8 µmol g−1 h−1 in pure water, 12.2 times higher than the bulk counterpart. The density functional theory revealed that the rate-limiting step energy barrier during the nitrogen fixation reaction can be lowered by oxygen vacancy engineering. This work would provide new insights into the synthesis of defect-state quantum dots and nitrogen photoreduction reactions.