Conversion of Carbon Dioxide into Chemical Vapor Deposited Graphene with Controllable Number of Layers via Hydrogen Plasma Pre-Treatment

Abstract

In this work, we report the conversion of carbon dioxide (CO₂) gas into graphene on copper foil by using a thermal chemical vapor deposition (CVD) method assisted by hydrogen (H₂) plasma pre-treatment. The synthesized graphene has been characterized by Raman spectroscopy, X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The results show the controllable number of layers (two to six layers) of high-quality graphene by adjusting H₂ plasma pre-treatment powers (100-400 W). The number of layers is reduced with increasing H₂ plasma pre-treatment powers due to the direct modification of metal catalyst surfaces. Bilayer graphene can be well grown with H₂ plasma pre-treatment powers of 400 W while few-layer graphene has been successfully formed under H₂ plasma pre-treatment powers ranging from 100 to 300 W. The formation mechanism is highlighted.

Keywords: carbon dioxide; chemical vapor deposition; graphene; hydrogen plasma.

Figure 1

Schematic diagram for the conversion of CO₂ to graphene on a Cu foil by the chemical vapor deposition (CVD) method.

Figure 2

Raman spectra of (a) graphene growth on Cu foils pre-treated with different H₂ rf plasma powers and (b) their intensity ratio values of I_D/I_G and I_2D/I_G. It should be noted that the H₂ gas still flowed over the sample with the rf power off in the case of “No-Plasma”.

Figure 3

Raman spectra of graphene growth on Cu foils pre-treated with H₂ rf plasma power of 400 W at different growth times.

Figure 4

(a) XRD patterns and (b) zoom graph of XRD patterns of the pristine Cu and the graphene growth on Cu foils pre-treated with different H₂ rf plasma powers.

Figure 5

FE-SEM images of (a) pristine Cu foil, Cu foil after CVD growth with (b) no and with hydrogen plasma pre-treatment using rf powers of (c) 100 W, (d) 200 W, (e) 300 W and (f) 400 W for 30 min.

Figure 6

Representative high-resolution TEM images of graphene edges produced via hydrogen plasma pre-treatments with rf powers of (a) 400 W, (b) 300 W, (c) 200 W, and (d) 100 W. The inset shows a typical SAED pattern of the bilayer graphene.

Figure 7

Sheet resistance of graphene on Cu foil as a function of the H₂ plasma power.

Figure 8

(a) Photograph of the real sample (Cu foil) after graphene growth with H₂ plasma pre-treatment at 400 W for 30 min. (b–f) FE-SEM images of bilayer graphene at five different regions on the Cu foil.