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

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 (nD) and mean distance between defects (LD) 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 nD, and then it experienced a rapid increase as nD further increased. However, once the defect density surpassed a critical value of about 1.8 × 1012 cm-2 (LD < 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.

Double hydrogen-bonding pH-sensitive hydrogels retaining high-strengths over a wide pH range.

Traditional pH-sensitive hydrogels inevitably suffer strength deterioration while the responsive weak acid or base groups are in the ionized state. In this study, we report on a facile approach to fabricate a novel pH-sensitive high-strength hydrogel from copolymerization of two hydrogen-bonding motif-containing monomers, 3-acrylamidophenylboronic acid and 2-vinyl-4,6-diamino-1,3,5-triazine with a crosslinker N,N-methylenebisacrylamide through hydrophilic optimization of the comonomer oligo(ethylene glycol) methacrylate. The double hydrogen bonding hydrogel exhibits both high tensile and compressive strengths over a broad pH range due to the unique ability to maintain at least one type of hydrogen-bonding crosslink over the whole course of pH change.