Regulation of heterogeneous electron transfer reactivity by defect engineering through electrochemically induced...

Enhancing the electrochemical activity of graphene holds great significance for expanding its applications in various electrochemistry fields. In this study, we have demonstrated a facile and quantitative approach for modulating the defect density of single-layer graphene (SLG) via an electrochemically induced bromination process facilitated by cyclic voltammetry. This controlled defect engineering directly impacts the heterogeneous electron transfer (HET) rate of SLG. By utilizing Raman spectroscopy and scanning electrochemical microscopy (SECM), we have established a correlation between the HET kinetics and both the defect density (n_D) and mean distance between defects (L_D) of SLG. The variation of the HET rate (k⁰) with the defect density manifested a distinctive three-stage behavior. Initially, k⁰ increased slightly with the increasing n_D, and then it experienced a rapid increase as n_D further increased. However, once the defect density surpassed a critical value of about 1.8 × 10¹² cm^-2 (L_D < 4.2 nm), k⁰ decreased rapidly. Notably, the results revealed a remarkable 35-fold enhancement of k⁰ under the optimal defect density conditions compared to pristine SLG. This research paves the way for controllable defect engineering as a powerful strategy to enhance the electrochemical activity of graphene, opening up new possibilities for its utilization in a wide range of electrochemical applications.