Triconstituent Co-assembly Synthesis of N , S-Doped Carbon-Silica Nanospheres with Smooth and Rough Surfaces

a Department of Chemical Engineering, Curtin University, Perth, WA 6845, Australia. b Centre for Microscopy, Characterisation and Analysis (CMCA), The University of Western Australia (M010), 35 Stirling Highway, Crawley WA 6009, Australia c Department of Imaging and Applied Physics, Curtin University, Perth, WA 6845, Australia d Department of Chemistry, Kent State University, Kent, Ohio 44242, United States

Two-electrode electrochemical measurements: These measurements were performed in a two electrode cell (capacitor) using 6.0 M KOH electrolyte solution.For the preparation of one electrode, 80 wt% of active material was mixed with 5 wt% of PTFE binder (PTFE 60 wt% dispersion in ethanol) to form a slurry.The slurry was spread onto a nickel foam (1 cm 2 ) under 10 MPa, followed by drying at 100 °C to prepare an electrode (1.0 mm thick, ~5 mg).After that, two electrodes with the same weight were put together, and then a polypropylene membrane was sandwiched between them as a separator.Two identical electrodes were used as cathodes and anodes for the cell configuration.The working electrode was vacuum-impregnated with the electrolyte for 30 min before electrochemical tests.Cyclic voltammetry (CV) was applied to the electrodes between 0 V and -0.8 V at scanning rate between 10 mV/s and 500 mV/s.Electrochemical measurements under acidic conditions: 3 mg of the carbon-silica particles were dispersed in 3 mL of 0.2 % Nafion aqueous solution by ultrasonication.10 μL of the dispersion was dipped onto the glassy carbon electrode (5 mm in diameter) and dried under ambient conditions.The electrode was then used as the working electrode in a 3-electrode electrochemistry system.In the system, Ag/AgCl electrode (in 3M KCl) and Pt wire were used as the reference electrode and the counter electrode respectively.1 M H 2 SO 4 aqueous solution wwas used as the electrolyte.Cyclic voltammetry (CV) was applied to the working electrode between 0 V and -0.8 V at scanning rate between 10 mV/s and 500 mV/s.Figure S8 shows the CV curves recorded for N,S-CSS and N,S-CSR-1 using a two-electrode system in the range from -0.8 V to 0.0 V at different scan rates.The specific capacitance obtained for N,S-CSS (83 F/g) is higher than that (~60 F/g) measured for N,S-CSR-1 (Figure S8 and Table S6).This value corresponds with the CV profiles that measured in a three-electrode system.

Section S2. Results, Table and Figures
The three-electrode method used often in electrochemical measurements has been reported is numerous works such as J. Power Sources, 2014, 246, 402-408 and Chem.Commun., 2015, 51, 2518-2521.Ag/AgCl electrode was used as reference electrode in 6M KOH solution in the range from -0.8 V to 0.2 V. Figure S9 shows the CV curves recorded for N,S-CSS and N,S-CSR-1 using a three-electrode system (1 M H 2 SO 4 ) in the range from -0.8 V to 0.0 V at different scan rates.The specific capacitance obtained for N,S-CSS and N,S-CSR-1 are 10 and 18 F/g.

Figure
Figure S2.(a) STEM and EDS elemental mapping of N,S-dually functionalized polymer-silica spheres without hydrothermal treatment (N,S-PSS).(b) STEM and EDS elemental mapping of N,S-dually functionalized polymer-silica spheres with hydrothermal treatment (N,S-PSR).

Figure S5 .
Figure S5.The relationship between particle size of N,S-dually functionalized carbon-silica and the molar ratio of TESPTS/AP.

Figure S6 .
Figure S6.The relationship between particle size of hollow silica and the molar ratio of TESPTS/AP.

Figure S8 .
Figure S8.CV profiles of N,S-CSS (a) and N,S-CSR-1 (b) measured in two-electrode system.

Table S1 .
Physical properties of N,S-dually functionalized carbon-silica spheres a Specific surface area was calculated by BET method.b Nonlocal density functional theory (NLDFT) was utilized to obtain the pore volume and pore size distribution.c Mean particle size was estimated by SEM and TEM analysis.d Theoretical molar ratio S/N.

Table S2 .
Element analysis of nitrogen-doped carbon materials

Table S3 .
Particle size and shell thickness of silica samples

Table S4 .
A comparison of the recently reported porous carbons for CO 2 capture with the data reported in this work.