Rational design of 3D N-doped graphene with a holey structure as a bifunctional electrode for sensitive methyl...

N-doped graphene with nano-sized holes possesses abundant electrochemically active sites at the exposed edge and an open porous structure, leading to a better electrochemical performance and faster electron and ion transport than the basal planes in graphene. In this study, three-dimensional graphene with a porous structure and abundant doped N (3d-NHG) were synthesized as bifunctional electrodes for methyl parathion (MP) detection and supercapacitors. The roles of N-doping and the holey construction in the electrochemical performance of the 3d-NHG were systematically investigated through a combined theory-experiment strategy. The 3d-NHG-based electrochemical sensor successfully detected methyl parathion in the range of 38 nm-380 μM with a low detection limit (2.27 nM) and superior sensitivity. Furthermore, the 3d-NHG also demonstrated potential for use in supercapacitors with a specific capacitance of 207 F g^-1 at 1 A g^-1 and excellent rate capability (76% capacitance retention at 10 A g^-1). Density functional theory calculations revealed that the exposed carbon sites at the edge are the reactive sites for species adsorption. Moreover, the holey structure in 3d-NHG plays a dominating role in electrochemical processes and in the enhanced electrocatalysis. This work provides guidance for the rational design of high-performance bifunctional electrodes for MP detection and supercapacitors by defect engineering.