Three-Dimensional Alkalized V₂CT_x MXene/NH₂-Graphene Heterojunction Nanocomposites for Ammonia Detection at Room Temperature

Two-dimensional MXene is considered a potential gas sensing material owing to its excellent conductivity, solution processability, plentiful surface terminations, and alterable interlayer spacing. Herein, we present the composites of the alkalized V₂CT_x MXene and NH₂-graphene (NG) prepared by simple sonication dispersion for ammonia (NH₃) detection at room temperature. The alkalized V₂CT_x MXene was negatively charged, owing to the presence of abundant oxygen-containing functional groups, which could interact with NG through electrostatic attraction. The characterization results indicated that NG mainly connects to the surface of the alkalized V₂CT_x MXene nanosheets. The gas response of the three-dimensional alkalized V₂CT_x MXene/NH₂-graphene (AVNG) sensor was 21 times stronger than that of the alkalized V₂CT_x MXene. Furthermore, the fabricated sensor based on the AVNG composites exhibited excellent selectivity to NH₃, a moderate response/recovery time, good durability, and stability. The gas sensing mechanism of the AVNG sensor was evaluated, and the synergistic effect of the interlayer swelling and n-p heterojunctions was proposed.