Fig. 1 Diagram and characterizations of MoS₂, MoS₂-A and MoS₂-DMA. (a) Schematic illustration for fabricating various MoS₂. (b) XRD patterns and (c, d, e) TEM images of (c) MoS₂, (d) MoS₂-A and (e) MoS₂-DMA. Insets of (c), (d) and (e) are their SEM images.

Fig. 2 Characterizations of MoS₂ with varied interlayer structures in control experiments. (a) XRD patterns of MoS₂ received with a low S/Mo feeding ratio of 2.0, and with additional NH₄Cl or (CH₃)₂NH₂Cl. (b) XRD patterns of MoS₂-DMA, MoS₂-DEA and MoS₂-DPA. (c) Schematic illustration for various intercalants and the corresponding interlayer structures. (d) Water CA test results.

Fig. 3  Characterization of MoS₂ phase transition from 2H to 1T along with interlayer expanding. (a) FT magnitudes of the k²[x(k)] EXAFS spectra and XPS profiles of (b) Mo and (c) S of MoS₂, MoS₂-A and MoS₂-DMA. (d) AC-TEM images and (e) HAADF-STEM images along with elemental mapping of MoS₂-DMA.

Fig. 4  Electrocatalytic performance of various MoS₂ along with the expanded interlayers. Polarization curves and Nyquist plots (at −0.45 V) of (a) MoS₂, (b) MoS₂-A, (c) MoS₂-DMA without and with 35 mM FAL. (d) FOL Faradaic efficiency, and (e) FAL conversion and FOL selectivity at different potentials. (f) Comparison of the ECH performance over various MoS₂ and metals at −0.25 V (CC: carbon cloth, Pt: commercial 40 wt% Pt/C loaded on CC, Ag: electrodeposited Ag on CC, Pd: Pd nanocrystals loaded on CC, Ni and Cu: commercial Ni and Cu foams).

Fig. 5  Theoretical calculation of the efficient FAL ECH on the MoS₂-DMA. (a) Electron density diagram and (b) PDOS of MoS₂, MoS₂-A and MoS₂-DMA. (c) HBE and FBE on the Mo and S sites of MoS₂, MoS₂-A and MoS₂-DMA models. The signs of (hkl)-Mo and (hkl)-S denote for the Mo and S sites on specific facets. (d) Comparison of three key factors (HBE, FBE and CA) of MoS₂, MoS₂ and MoS₂-DMA. The HBE and FBE on the Mo-sites of (100) plane are taken for comparison, because such sites have been identified effective for chemisorption and electrocatalysis.

Fig. 6   ECH of 5-HMF, CAL and p-NP over MoS₂-DMA operated at -0.25 V vs. RHE for 2 h, with Na₂B₄O₇ aqueous solution (pH 9.18) containing 0.035 mol/L substrate as the electrolyte.