Synergistic strain and N-doping for creating physical orientation selectivity in chemical etching of graphene nanoribbons

Abstract

The controlled synthesis of graphene nanoribbons (GNRs) necessitates precise selectivity in physical orientation during the etching process. However, traditional chemical selectivity methods struggle to etch graphene due to its symmetrical structure and uniform chemical bonds, which result in no differences in reaction pathways or products. We introduce an innovative method that overcomes these limitations by combining physical stress with nitrogen doping, thereby creating new chemical selectivity for oriented etching. This precise synthesis method produces GNRs with adjustable widths ranging from 103 to 16 nm and controlled zigzag edges precisely decorated with peripheral N-dopants. In a cylindrical container, spontaneous self-bending of graphene oxide sheets in ammonia medium can induce strain on the carbon matrix. This strain stretches the C–C bonds and rearranges epoxy-pair chains on the carbon skeleton, directing the graphene oxide etching perpendicular to the strain with the aid of N-aligning, resulting in the production of GNRs. By simply regulating bending strain, we obtained a series of zigzag GNRs with tailorable widths and peripheral N-dopant concentrations. This approach provides a powerful toolbox for fine-tuning the oriented etching geometric features and their electrical and chemical properties in two-dimensional materials (e.g., superior performance of GNRs in electrocatalytic oxygen reduction reactions demonstrated here).