Synthesis of graphene materials by electrochemical exfoliation: Recent progress and future potential

Abstract

Synthesis of structurally controlled graphene materials is critical for realizing their practical applications. The electrochemical exfoliation of graphite has emerged as a simple method to produce graphene materials. This review examines research progress in the last 5 years, from 2015 to 2019. Graphene material synthesis methods generally have a trade‐off between increasing production yield and achieving better material property control. The synthesis conditions for synthesizing pristine graphene, graphene oxide (GO), and graphene composites are significantly different. Thus, in this review, we first discuss synthesis methods for graphene materials with high C/O ratios from four aspects: graphite electrodes, equipment engineering, electrolytes, and additional reduction methods. Next, we survey synthesis methods for GO and examine how the pretreatment of the graphite electrodes, electrolytes, and operation parameters, such as applied voltages, electrolyte temperatures, and mechanical forces, affect the quality of GO. Further, we summarize electrochemical exfoliation methods used to dope graphene materials, introduce covalent functional groups, incorporate various nanoparticles, and assembly of graphene architectures. For all synthesis methods, we compare the properties of resulting graphene materials such as C/O ratios, lateral size, layer numbers, and quality characterized by Raman spectroscopy. Lastly, we propose our perspectives on further research. We hope this review stimulates more studies to realize the on‐demand production of graphene materials with desired properties using electrochemical exfoliation methods.

Anchoring SnS2 on TiC/C Backbone to Promote Sodium Ion Storage by Phosphate Ion Doping

“…The crystal structures of SnS 2 @TiC/C and P-SnS 2 @TiC/C are illustrated in Figure 4a,b. Compared with the SnS 2 @TiC/C, the computed model of P-SnS 2 @TiC/C shows a novel P-O-Sn bonding after PO 4 3− doping, consistent with the XPS results above. Moreover, Figure 4c,d shows the total density of state (DOS) of band electrons for SnS 2 @TiC/C and P-SnS 2 @TiC/C.…”

“…Along with the deterioration of environment pollution and intensification of the energy crisis, exploring green and renewable technology for energy storage and conversion is becoming an urgent issue. [1][2][3] Despite great success in commercialization of lithium ion batteries (LIBs), [4][5][6] the high cost and scarcity application in SIBs because of their high theoretical capacity, high redox activity, and lamellar structure similar to graphite. Among these materials, SnS 2 featuring a typical CdI 2 -type crystal structure has been considered as a prospective candidate as anode for SIBs on account of its high specific capacity up to 1137 mAh g −1 , large interlamellar spacing of 0.59 nm, and low operation potential.…”

“…3− -doped SnS 2 (P-SnS 2 ) for sodium ion storage. It would be interesting to investigate the synergetic effect of TiC/C skeleton and PO 4 3− doping strategy on SnS 2 for sodium ion storage. In this work, for the first time, we report phosphate ions-doped SnS 2 nanoflakes on highly conductive TiC/C arrays forming highquality P-SnS 2 @TiC/C arrays as anode of SIBs.…”

“…After phosphorization with NaH 2 PO 2 , the obtained P-SnS 2 @TiC/C arrays show similar morphology to the SnS 2 @TiC/C, although the surface of P-SnS 2 nanosheets is a bit rougher than the pure SnS 2 (Figures 1f,g and 2e), implying that the phosphorization process will not damage the material structure. The difference in microstructure after PO 4 3− doping is distinguished by HRTEM and SAED images. The lattice spacing of SnS 2 @TiC/C is around 0.278 nm (Figure 2d), corresponding to the (101) plane of SnS 2 .…”

“…The CVs overlap after the first cycle, indicating excellent reversibility of the discharge/charge process. Moreover, compared to SnS 2 @TiC/C electrode, the P-SnS 2 @TiC/C electrode shows a higher cathodic peak potential and higher current density, revealing its better electrochemical reactivity due to doping of PO 4 3− . The galvanostatic charge-discharge curves of the designed P-SnS 2 @TiC/C and SnS 2 @TiC/C are presented in Figure 5c.…”