Supporting Information

Influence of graphene-coating on supercapacitive behavior of sandwich-like N- and O-enriched porous carbon/graphene composites in aqueous and organic electrolytes

Shuwen Zhou • Qinxing Xie • Shihua Wu • Xiaolin Huang • Peng Zhao

S. Zhou • Q. Xie* • X. Huang

Tianjin Key Laboratory of Advanced Fibers and Energy Storage, School of Materials Science and Engineering, Tianjin Polytechnic University, Tianjin 300387, China

E-mail:

S. Wu • P. Zhao

Department of Chemistry, Nankai University, Tianjin 300017, China


Electrochemical measurements

The measurements were carried out in a two-electrode cell using a CHI 660E electrochemical workstation (CH Instrument, China). The gravimetric specific capacitance for materials was calculated according to CV and GCD curves by Eqs. (1) and (2), respectively [1-3] :

(1)

(2)

where S is the potential scan rate, I is the current,ΔV is the potential range, Δt is the discharge time, and m is the mass of active material on each electrode. The volumetric specific capacitance was calculated by Eqs. (3) and (4) [3] :

Cv = r ´ Cm (3)

(4)

where r is the particle density and Vt is the total pore volume of the materials, ρT is the true density of carbon (2 g cm-3 ). The gravimetric energy density and power density for the assembled cells were calculated by Eqs. (5) and (6) [1]:

(5)

(6)

where Ccell, ΔV and Δt are the gravimetric specific capacitance of the cell (Cm/4), voltage change with deducted IR drop and discharge time, respectively. The volumetric energy density Ev and power density Pv were determined from the gravimetric energy density and power density multiplied by a factor of r [4].


Fig.S1 (a-b) CV curves of NAC@Gr3 at various scan rate from 5 to 400 mV s-1, (c-d) GCD curves of NAC@Gr3 at various current densities from 0.1 to 20 A g-1 in 6 M KOH aqueous electrolyte.


Fig.S2 (a) CV curves at various scan rate from 5 to 100 mV s-1, and (b) GCD curves at various current densities from 1 to 20 A g-1 for NAC@Gr5 in 1 M TEABF4/AN electrolyte.

References

1.  Conway BE, Electrochemical supercapacitors: scientific fundamentals and technological applications (Plenum Press, New York, 1999)

2.  Xie Q, Zheng A, Zhai S, Wu S, Xie C, Zhang Y, Guan Y (2016) J Solid State Electrochem 20:449-457.

3.  Xie Q, Bao R, Zheng A, Zhang Y, Wu S, Xie C, Zhao P (2016) ACS Sustainable Chem Eng 4:1422.

4.  Li Y, Zhao D (2015) Chem Commun 51: 5598.

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