Three-Dimensional-Structured Boron- and Nitrogen-Doped Graphene Hydrogel Enabling High-Sensitivity NO₂ Detection at Room Temperature

Heteroatom-doping has been proved as an effective method to modulate the electronic, physical, and chemical properties of graphene (Gr). Developing a new strategy of heteroatom-doping for high-performance gas sensing is a pivotal issue. Here, we demonstrate novel Gr-based gas sensors through three-dimensional (3D)-structured B-/N-doping nanomaterials for high-performance NO₂ sensing. The 3D porous B- and N-doped reduced graphene oxide hydrogels (RGOH) are synthesized via one-step hydrothermal self-assembly and employed as transducing materials to fabricate roomerature high-performance chemiresistors. The systematic characterizations of the as-synthesized B- and N-RGOH clearly show the uniform doping of the B and N heteroatoms and the formation of B and N components with C/O. In comparison with the pristine RGOH counterpart, the 3D B- and N-RGOH sensors exhibit 38.9 and 18.0 times enhanced responses toward 800 ppb NO₂, respectively, suggesting the remarkable doping effect of the heteroatoms in improving the sensitivity. Significantly, B- and N-RGOH display the exceptionally low limit of detection of 9 and 14 ppb NO₂, respectively, which are much lower than the threshold limit recommended by the U.S. Environmental Protection Agency. In addition, the developed NO₂ sensors show good linearity, reversibility, fast recovery, and impressive selectivity. This work opens up a new avenue to fabricate roomerature and high-performance NO₂ sensors by incorporating B and N heteroatoms into 3D RGOH via a convenient hydrothermal self-assembly approach.