Silicon Radical‐Induced CH₄ Dissociation for Uniform Graphene Coating on Silica Surface

Abstract

Due to the manufacturability of highly well‐defined structures and wide‐range versatility in its microstructure, SiO2 is an attractive template for synthesizing graphene frameworks with the desired pore structure. However, its intrinsic inertness constrains the graphene formation via methane chemical vapor deposition. This work overcomes this challenge by successfully achieving uniform graphene coating on a trimethylsilyl‐modified SiO2 (denote TMS‐MPS). Remarkably, the onset temperature for graphene growth dropped to 720 °C for the TMS‐MPS, as compared to the 885 °C of the pristine SiO2. This is found to be mainly from the Si radicals formed from the decomposition of the surface TMS groups. Both experimental and computational results suggest a strong catalytic effect of the Si radicals on the CH4 dissociation. The surface engineering of SiO2 templates facilitates the synthesis of high‐quality graphene sheets. As a result, the graphene‐coated SiO2 composite exhibits a high electrical conductivity of 0.25 S cm−1. Moreover, the removal of the TMP‐MPS template has released a graphene framework that replicates the parental TMS‐MPS template on both micro‐ and nano‐ scales. This study provides tremendous insights into graphene growth chemistries as well as establishes a promising methodology for synthesizing graphene‐based materials with pre‐designed microstructures and porosity.

Progress in templated nanocarbons and related materials chemistry

“…CH 4 -CVD on SiO 2 is approximately 640 times higher than that of the carbon layer produced through C 2 H 2 -CVD followed by annealing at 900 °C[50]. This underscores the superiority of the CH 4 -to-C reaction.…”

“…We have elucidated several critical factors for the successful synthesis of GMS, including the curvature, morphology, and stacking of the graphene walls [49]. More recently, the template type has been extended to include surface-modified SiO 2 [50].…”

“…Unlike Al 2 O 3 , MgO, and CaO, the surface oxygen of SiO 2 hardly reacts with CH 4 at high temperatures, making it unable to achieve catalytic growth of single-layer graphene below the thermodynamic decomposition temperature of CH 4 (∼950 °C) [50]. Hoshikawa et al…”

“…reported that the chemical modification of SiO 2 with trimethylsilyl (TMS) groups renders its surface active for acetylene (C 2 H 2 ) CVD at 600 °C [63]. Thus, we have investigated the impact of the TMS modification of SiO 2 on CH 4 -CVD at 900 °C and found that monocoordinated Si radicals generated through the thermal decomposition of TMS significantly enhance the catalysis of the CH 4 -to-C reaction [50]. Notably, the conductivity of a graphene layer formed through…”

Extraordinary Capacitance and Stability of Carbon Electrode for Electrochemical Capacitors

“…45 GMS can be synthesized via specific chemical vapor deposition, 49,50 allowing the growth of a minimally stacked graphene layer onto the entire surface of metal oxide nanoparticles such as Al 2 O 3 , MgO, and surface-modified SiO 2 . 48,51 Following the template removal under conditions that prevent additional stacking, 52 edge sites are removed via zipping reactions occurring at temperatures exceeding 1600 °C. 53 GMS possesses developed mesoporosity, a high specific surface area (³2000 m 2 g ¹1 ), excellent conductivity, and high oxidation resistance, 45,54 all of which align with the characteristics anticipated in structures like carbon schwarzites composed of edge-free and minimally stacked graphene framework.…”