Three-Dimensional Alkalized V₂CT_<i>x</i> 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 V2CTx MXene and NH2-graphene (NG) prepared by simple sonication dispersion for ammonia (NH3) detection at room temperature. The alkalized V2CTx 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 V2CTx MXene nanosheets. The gas response of the three-dimensional alkalized V2CTx MXene/NH2-graphene (AVNG) sensor was 21 times stronger than that of the alkalized V2CTx 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