Fig. 1. Characterization of the Nb₂C/MoS₂ heterostructure. (a) Schematic illustration of the in situ synthesis of the Nb₂C/MoS₂. (b) Transmission electron microscope (TEM) image of Nb₂C/MoS₂. (c) Elemental mapping images of Nb₂C/MoS₂, upper left plane: Nb (yellow), upper right plane: Mo (cyan), left lower plane: S (blue), and right lower plane Merge. (d) High-resolution transmission electron microscopy (HRTEM) of Nb₂C/MoS₂. (e) Selected area electron diffraction (SAED) pattern of Nb₂C/MoS₂. (f) Raman spectra of Nb₂C/MoS₂. (g) XRD pattern of Nb₂C/MoS₂, Nb₂C, and Nb₂AlC.

Fig. 2. XPS spectra of the Nb₂C/MoS₂ and Nb₂C: (a) C 1s, (b) Nb 3d, (c) O 1s, (d) S 2p, (e) F 1s, and (f) valence band.

Fig. 3. The calculated work functions of (a) Nb₂CF₂/MoS₂, (b) Nb₂CO₂/MoS₂, (c) Nb₂C(OH)₂/MoS₂. The charge-transfer and band alinement diagram of (d) Nb₂CO₂/MoS₂ and (e) Nb₂C(OH)₂/MoS₂.

Fig. 4. (a) UV-vis spectrum of Nb₂C solution with different concentrations. Inset: absorbance as a function of concentration. (b) DFT calculated absorption spectrum of Nb₂C with different terminations. (c) UV-vis spectrum of Nb₂C/MoS₂ solution. (d) DFT calculated absorption spectrum of Nb₂C/MoS₂ with different terminations.

Fig. 5. OA Z-scan results of Nb₂C/MoS₂ and Nb₂C with an excitation wavelength of (a) 1300 nm and (b) 1550 nm. The corresponding nonlinear transmittance curves under excitation optical intensity are shown in (c) and (d). (e) Histogram of I_s and α_NL. (f) Schematic diagram of the transfer process of photogenerated carriers and enhanced nonlinear absorption process in Nb₂C/MoS₂.