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Synthesis of 3D Bicontinuous Cu-Ni Alloy Scaffolds for Controlled Growth of Turbostratic Graphene

  • Author(s): Zhang, Zhengyu
  • Advisor(s): Ragan, Regina
  • et al.
Abstract

3-dimensional (3D) porous graphene is a promising platform for applications such as catalysis, sensors, and energy storage. In this thesis, bicontinuous interfacially jammed emulsion gel (bijel) templates are formed and chemically and thermally processed into sacrificial porous Cu-Ni alloy scaffolds which in turn are used for chemical vapor deposition (CVD) of graphene. Metal scaffolds formed from the bijel structure have large specific surface area and inherit the co-continuous property from their parent bijel. However, graphene grown via CVD on bicontinuous nickel scaffolds (biNi) will typically produce thick graphene layers due to the high carbon solubility in Ni unless the CVD growth is limited to short growth times of a few seconds. In the latter case, number of layers may be variable across the sample due to difficulties in controlling deposition kinetics in short growth times. In addition, thick graphite layers may form in the Ni grain boundaries leading to highly non uniform number of layers in 3D samples. Previous reports have shown that the number of layers and uniformity of CVD graphene can be controlled when using the Cu-Ni alloys as scaffolds. In this case, research has been limited to CVD growth on 2-dimensional Cu-Ni alloy surfaces. Here, in this thesis, the fabrication of 3D bicontinuous Cu-Ni alloy metal scaffolds(bi-CuNi) are successfully achieved. By varying electrochemical processing parameters, bi-CuNi with porous morphology containing 46.8% and 35.8% Cu in weight percentage are produced. When comparing the morphology and number of layers of resultant CVD graphene growth on the alloy scaffolds using the same CVD growth parameters on both samples, Raman spectroscopy measurements show many regions with a high 2D mode intensity with the higher Cu alloy concentration in the scaffold. Raman analysis showing that 3D graphene from bi-CuNi via CVD (bi-CuNi-3DG) exhibits turbostratic stacking in many regions of the sample. Turbostratic graphene can exhibit similar properties as single-layer graphene (SLG), indicating that emphasis on tuning physical properties of scaffold alloys has promise to yield 3D graphene structures with excellent electronic properties. In future work, precise control of Cu concentration in bi-CuNi is expected to control both graphene layer number and stacking, and thereby the electronic properties of the resultant 3D graphene architectures for numerous applications.

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