Fig. 3: Mapping the distribution of ζ potential.

a, b Schematic illustrations of ion distribution in the EDL on MoS₂ at ionic strengths of 0.3 mM and 3 mM KCl, respectively. Molecular models were produced by VESTA⁴⁷. c Spatial distribution of ζ potential on the MoS₂ surface as a function of pH in flowing 0.3 mM and 3 mM KCl solutions. Scale bar: 3.0 μm. V_DC = −0.3 V, V_pp = 200 mV. d A box plot depicts the numerical distribution of ζ potential values on the MoS₂ surface (delineated by the dashed line in Fig. 3c) for two ionic strengths as a function of pH, revealing that spatial variation yields pronounced differences in ζ potential across the nanosheet within a single chemical environment. The box plot shows the median (center line), interquartile range (box limits), whiskers extending to 1.5× interquartile range, and 12249 independent pixels per box. e Schematics of the ζ potential in the Helmholtz and diffuse layers on the surface of MoS₂ nanosheets with varying thicknesses. C_q, C_h and C_dl represent the capacitances of the MoS₂, Helmholtz layer, and diffuse layer, respectively; and \({R}_{{{{{\rm{MoS}}}}}_{2}}\), R_h and R_s denote their resistances. f ζ potential increasing with pH in the triangular areas of the MoS₂ nanosheet marked in Fig. 3c. Source data are provided as a Source Data file.