Subsurface Mo Vacancy in Bismuth Molybdate Promotes Photocatalytic Oxidation of Lactate to Pyruvate

Disclosing the role of subsurface metal defects in photocatalysts remains challenging, although defect engineering has been a fundamental method for manipulating the photocatalytic transformation performance. Herein, the subsurface Mo vacancy-rich Bi2MoO6 was prepared and the role of its effects on photocatalysis was revealed. The presence of metal vacancy enhances the separation efficiency of photogenerated carriers through both the holes captured by the oxygen atoms neighboring the Mo vacancy and the generation of an internal electric field, which is revealed by experimental results and density functional theory calculations. The boosted separation efficiency of electron–hole pairs improves the generation of 1O2, which is the final active species for photocatalytic oxidation of ethyl lactate. The conversion of ethyl lactate reaches to >99% over the subsurface Mo vacancy-rich Bi2MoO6 after 3 h of illumination, much higher than that of bulk Bi2MoO6, which gives only 28.6%. Meanwhile, the yield of ethyl pyruvate is 90.2%, which is the highest value in heterogeneous systems using molecular oxygen as oxidant. Moreover, the catalyst is rather stable and can be applied for the selective oxidation of other hydroxyl compounds. This work unveils the role of metal defects engineering in affecting electron–hole separation, highlighting possible opportunities for highly efficient photocatalytic organic transformation.