Hydrogen‐Enhanced Catalytic Conversion of Amorphous Carbon to Graphene for Achieving Superlubricity

Abstract

The solid‐state conversion of amorphous carbon into graphene is extremely difficult, but it can be achieved in the friction experiments that induce macroscale superlubricity. However, the underlying conversion mechanisms remain elusive. Here, the friction experiments with Cu nanoparticles and (non‐hydrogen (H) or H) a‐C in vacuum, show the H‐induced conversion of mechanical to chemical wear, resulting in the a‐C's tribosoftening and nanofragmentating that produce hydrocarbon nanoclusters or molecules. It is such exactly hydrocarbon species that yield graphene at hydrogen‐rich a‐C friction interface, through reaction of them with Cu nanoparticles. In comparison, graphene isn't formed at Cu/non‐H a‐C friction interface. Atomistic simulations reveal the hydrogen‐enhanced tribochemical decomposition of a‐C and demonstrate the energetically favorable graphitization transformation of hydrocarbons on Cu substrates. The findings are of importance to achieve solid‐state transformation between different carbon allotropes and provide a good strategy to synthesize other graphitic encapsulated catalysts with doped elements.

Toward three-dimensionally ordered nanoporous graphene materials: template synthesis, structure, and applications

“…These insights into the atomic level structure of NPGs including the chemical and topological defects will be conducive to further control of high-quality NPGs. Advanced characterization, including computational 168,169 and experimental (Raman spectroscopy, 86 angle-resolved photoemission spectroscopy, 23,170 X-ray absorption fine structure spectroscopy, 171,172 electron energy loss spectroscopy, 173 X-ray photoelectron spectroscopy, 171 steady-state absorption spectroscopy, and neutron diffraction 174 ) approaches (Fig. 8), will provide a more sophisticated understanding and control of novel 3D graphene materials at the atomic level.…”

Macroscale Superlubricity on Nanoscale Graphene Moiré Structure‐Assembled Surface via Counterface Hydrogen Modulation

“…Material Preparation: DLC coatings including DLC0, DLC12 and DLC25 (with a thickness of 500 nm) [47] were prepared on Si substrates by an unbalanced magnetron sputtering system using the mixed gas of Ar and H 2 with the flow ratio of 1:0, 1:2, 1:6, 1:8, and 1:10. The preparation parameters of DLC included the substrate bias voltage of −700 V (pulsed frequency of 60 kHz and duty cycle of 0.6) and the carbon target power of 0.50 kW.…”

“…Characterization of Contact Regions: The structure and chemical composition of GMS-assembled coating were detected by Raman spec-trometer (Jobin-Yvon HR-800), scanning electron microscopy (SEM, JSM-5601LV) and Transmission Electron Microscope (TEM, FEI Techanai G 2 ). To avoid unintentional damage of the samples, the laser intensity in Raman tests was strictly controlled below 0.5 MWm −2 , (because carbon materials did not suffer damage in this range [43,47] ). The Raman mapping images obtained from 8 μm×40 μm region were measured with an 1 μm step size in the y direction, a 3 μm step size in the x direction and an acquisition time of 10 s. The morphologies of ball-milled balls, wear tracks and scars were analyzed using 3D white light interferometer (KLA-Tencor, MicroXAM-800) and optical microscope (Olympus-BX35).…”

Accelerating Macroscale Superlubricity through Carbon Quantum Dots on Engineering Steel Surfaces

“…Unfortunately, the realization of most solid superlubricity usually requires strict conditions, such as perfect crystal quality, vacuum or inert atmosphere, and complex surface structures. [19][20][21][22] Liquid superlubricity is more achievable than solid superlubricity under environmental conditions, making it a promising option for practical engineering applications. [16,23,24] Various liquid lubricants, such as ionic liquids, [25] polymer brushes, [26] multi-alcohol solutions, [27,28] and aqueous solutions of acids, [29,30] have demonstrated remarkable superlubricity properties.…”

“…Unfortunately, the realization of most solid superlubricity usually requires strict conditions, such as perfect crystal quality, vacuum or inert atmosphere, and complex surface structures. [ 19–22 ]…”