Nitrogen-Doped Graphene with Enhanced Room Temperature NH3 Gas Sensing Properties

Herein, nitrogen-doped wrinkled multilayer graphene sheets (N-doped graphene) are synthesized via a facile solvothermal route followed by NH3 atmosphere annealing at different temperatures. Systematic characterization by SEM, XRD, FTIR, Raman, and XPS confirms the successful incorporation of nitrogen with tunable configurations, i.e., pyridinic N, pyrrolic N, and graphitic N, whose relative fractions are strongly dependent on annealing temperature. Room-temperature gas sensing tests toward NH3 reveal that the G-600 (N-doped graphene annealed at 600 °C) sensor exhibits the highest response (4.76 toward 300 ppm NH3), about 7.8 times that of G-400 (a counterpart sample thermally treated at 400 °C), along with excellent selectivity, reproducibility, and stability. Density functional theory (DFT) calculations demonstrate that pyridinic N provides the strongest adsorption affinity for NH3 and the largest charge transfer, whereas graphitic N ensures superior electrical conductivity. The optimal performance of G-600 arises from a synergistic effect between abundant pyridinic N active sites for enhanced NH3 adsorption and sufficient graphitic N for efficient charge transport. This work not only elucidates the mechanism of nitrogen-configuration-governed sensing behavior but also offers a rational strategy for designing high-performance room-temperature NH3 sensors based on N-doped graphene.