1. (a-f) SEM and (g-l) TEM images of carbon precursors with different P123/SDS mass ratios

2. (a-e) SEM and (f-j) TEM images of carbon precursors after hydrothermal treatment for different periods

3. Morphology regulation mechanism of the horseshoe- shaped hollow porous carbon precursors

4. (a) N₂ adsorption-desorption isotherms and (b) pore size distribution curves of different samples

5. FT-IR spectra of D-xylose and different carbon precursors

6. (a) XPS total survey and (b) wettability of HNC_S-1.25-8, HNC_S-1.25-12, HNC_S-1.25-18, and HNC_S-1.25-24

7. (a) CV curves at 5-100 mV∙s^-1 and (b) GCD curves at 1-20 A∙g^-1 of HNC_S-1.25-12; (c) Specific capacitances and Coulombic efficiencies (inset) at 1-20 A∙g^-1, (d) relationship between specific capacitance with diameter of cavity at 1 A∙g^-1 and (e) Nyquist plots with equivalent circuit (inset) of different samples; (f) Cycling stability of HNC_S-1.25-12

S1. (a) SEM and (b-d) TEM images of HN_S-1.25-12

S2. (a, e) TEM images and (b-d) C, (f-h) O element mappings of (a-d) HN_S-1.25-12 and (e-h) HNC_S-1.25-12

S3. (a) Size distribution and Zeta potential, and (b) surface tension of micelle/emulsion in H₂O

S4. TG curves of SDS, P123 and different carbon precursors

S5. (a) XRD patterns, (b) Raman spectra of HN_S-1.25-12, HNC_S-1.25-8, HNC_S-1.25-12, HNC_S-1.25-18, and HNC_S-1.25-24

S6. (a) C1s and (b) O1s high resolution XPS spectra of HNC_S-1.25-8, HNC_S-1.25-12, HNC_S-1.25-18 and HNC_S-1.25-24

S7. (a) CV curves at 5 mV∙s^-1 and (b) GCD curves at 1 A∙g^-1 of different samples

S8. Electrochemical performance of different materials in two-electrode system

Table 1. Average diameters of particles, inner cavities, carbon walls, opening angles, and pH dependence of different samples

Table 1. Textural parameters of different samples

Table 2. Capacitive properties of doped-carbon materials reported in literature