Tailoring the Surface Oxygen Vacancies in Nanoporous BiOCl_0.8I_0.2 Nanoflowers for Photocathodic Sensing

Efficient photocatalytic reduction of electron acceptors is highly desirable for cathodic photoelectrochemical (PEC) sensors. Here, we report a facile and controllable strategy to tailor surface oxygen vacancies (OVs) in nanoporous BiOCl0.8I0.2 nanoflowers by postsynthetic treatment and explore the effects of the species and dosage of the reducing agent on the PEC properties of the photocatalyst. The results indicate that the surface oxygen vacancy concentration of BiOCl0.8I0.2 nanoflowers can be modulated by changing the dosage of glyoxal. The oxygen vacancy engineering of BiOCl0.8I0.2 nanoflowers can significantly facilitate the activation and reduction of electron acceptors (i.e., oxygen) in cathodic PEC sensing. In contrast to OV-deficient BiOCl0.8I0.2, the OV-rich BiOCl0.8I0.2-G2 (G2 means to treat with 0.075 mol/L of glyoxal) delivers high catalysis to the reduction of oxygen, making the photocurrent change value up to 8.5 times of the OV-deficient BiOCl0.8I0.2. The OV-rich BiOCl0.8I0.2-G2 is used as an efficient photocathodic material for the PEC detection of insulin, and it exhibits high selectivity and sensitivity. This work offers a versatile protocol for the in situ fabrication of controllable OV-rich bismuth oxyhalides for sensitive cathodic PEC analysis.