Solvent-Free Process to Produce Three Dimensional Graphene Network with High Electrochemical Stability

Abstract

Three-dimensional (3D) graphene has attracted increasing attention in electrochemical devices. However, the existing preparation technologies usually involve a solvent process, which introduces defects and functional groups into the 3D network. Here, we find the defects and functional groups influence the electrochemical stability of graphene. After an electrochemical process, the current decreases by more than 1 order of magnitude, indicating remarkable etching of graphene. To improve the electrochemical stability, we develop a solvent-free preparation process to produce 3D graphene for the first time. After growth on a 3D microporous copper by chemical vapor deposition (CVD), the copper template is removed by a high temperature evaporation process, resulting in 3D graphene network without any solvent process involved. The samples exhibit remarkably improved stability with durable time 2 times, compared with normal CVD samples, and 55 times, compared with reduced graphite oxide, and no obvious etching is observed at 1.6 V versus saturated calomel electrode, showing great potential for application in future 3D graphene-based high stable electrochemical devices.

3D Graphene Foam by Chemical Vapor Deposition: Synthesis, Properties, and Energy-Related Applications

“…Thus, to control the number of graphene layers and the porosity of the final graphene foams, different porous catalysts, and different synthesis conditions have been considered. To this end, the substrate skeletons range from foams [ 4 , 5 , 16 , 17 , 18 ] or films [ 19 ] to nanopowders [ 20 , 21 , 22 ], from metals to metal oxide [ 23 ], to metal salts [ 24 ] or seashells [ 14 ]. Regarding the distribution of the pores, they are either randomly distributed or well-ordered using 3D printing [ 25 ].…”

“…A 3D monolithic microporous copper template [ 21 ] with a pore size in the range of 10–20 µm obtained from copper powder allowed the synthesis of interconnected porous 3D graphene with a pore size 1–2 orders of magnitude smaller than those obtained on commercial nickel foam ( Figure 5 a). Furthermore, using a sublimation method to remove the Cu template, free-standing 3D graphene with high pore density and excellent mechanical properties was obtained without collapsing in the absence of the Cu skeleton ( Figure 5 b).…”

“…It is known that gaseous aliphatic hydrocarbons and hydrogen are dangerous and asphyxiating gases, extremely flammable, and can form explosive mixtures with air, which implies a high degree of safety precautions [ 41 ]. In order to overcome these safety issues, several studies reported cost-effective liquid carbon sources such as ethanol for growing single- and few-layer graphene on nickel foam [ 5 , 21 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 ]. In order to be used in CVD graphene synthesis, liquid precursors need to be transformed into gas before they reach the metallic catalyst.…”

“…However, unlike Huang et al [ 44 ], a lower heating ramp under forming gas (N 2 :H 2 = 95%:5%) was used [ 48 ]. In addition, a nickel-copper catalyst template and ethanol precursor were also used to grow 3D graphene networks at 1000 °C for 20 min under a hydrogen atmosphere [ 21 ].…”

“…However, other strong (HNO 3 and Fe(NO 3 ) 3 ) [ 39 , 55 , 56 , 57 ], or mild acids [ 58 ] have been proven as efficient etching solutions. A combination of electrochemical and chemical etching processes [ 22 ] and sublimation [ 21 ] methods have also been used to effectively etch the metallic template.…”