Sulfur-doped porous reduced graphene oxide hollow nanosphere frameworks as metal-free electrocatalysts for oxygen reduction reaction and as supercapacitor electrode materials

Abstract

Chemical doping with foreign atoms is an effective approach to significantly enhance the electrochemical performance of the carbon materials. Herein, sulfur-doped three-dimensional (3D) porous reduced graphene oxide (RGO) hollow nanosphere frameworks (S-PGHS) are fabricated by directly annealing graphene oxide (GO)-encapsulated amino-modified SiO2 nanoparticles with dibenzyl disulfide (DBDS), followed by hydrofluoric acid etching. The XPS and Raman spectra confirmed that sulfur atoms were successfully introduced into the PGHS framework via covalent bonds. The as-prepared S-PGHS has been demonstrated to be an efficient metal-free electrocatalyst for oxygen reduction reaction (ORR) with the activity comparable to that of commercial Pt/C (40%) and much better methanol tolerance and durability, and to be a supercapacitor electrode material with a high specific capacitance of 343 F g(-1), good rate capability and excellent cycling stability in aqueous electrolytes. The impressive performance for ORR and supercapacitors is believed to be due to the synergistic effect caused by sulfur-doping enhancing the electrochemical activity and 3D porous hollow nanosphere framework structures facilitating ion diffusion and electronic transfer.

Highly exposed copper oxide supported on three-dimensional porous reduced graphene oxide for non-enzymatic detection of glucose

“…Then NH2-SiO2/GO was pyrolyzed under an inert atmosphere and the subsequent elimination of the NH2-SiO2 template leaded to porous graphene [35]. It is thought that this kind of scenario may have led the porous structure.…”

“…Besides, the characteristic peak of GO at 10.4° in the XRD pattern disappeared, which indicates that GO has been reduced effectively during the synthesis process. The peaks at35.60°, 38.73°, 48.90°, 58.3°, 61.5° and 68.1° suggest the formation of CuO (JCPDS 48-1548). Compared with the reference card statistics of CuO, no other reflections for Cu metal or other copper-compound were observed.…”

Nitrogen-containing carbon microspheres for supercapacitor electrodes

“…On the other hand, the heteroatoms, such as nitrogen and sulfur, have been introduced into carbon materials in order to further improve electrochemical performance of carbon electrodes [21][22][23]. Nitrogen-containing carbon materials can be prepared by the carbonization of nitrogen-enriched polymers and materials, such as polyaniline, melamine, polypyrrole and so on [24][25][26][27][28][29][30][31][32].…”

Recent advances in flexible supercapacitors based on carbon nanotubes and graphene

“…In addition to combining the graphene film with pseudocapacitive materials at the nanoscale, direct doping of heteroatoms into carbon scaffolds also increases the pseudocapacitance [109][110][111]. It has been shown that C-S bonds near edges or defects are active sites which influence the charging of the electrical double layer and facilitate the pseudocapacitive behavior [112]. Therefore, a bottom-up method has been developed to synthesize sulfur doped graphene (SG) films .…”