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Title: Reactive Intermediates or Inert Graphene? Temperature- and Pressure-Determined Evolution of Carbon in the CH 4–Ni(111) System

Atomic-level identification of carbon intermediates under reaction conditions is essential for carbon-related heterogeneous catalysis. Using the in operando technique of near-ambient-pressure X-ray photoelectron spectroscopy, we have identified in this paper various carbon intermediates during the thermal decomposition of CH 4 on Ni(111), including *CH, *C 1/Ni 3C, *C n (n ≥ 2), and clock-reconstructed Ni 2C at different temperature regions (300–900 K). These “reactive” carbon precursors can either react with probing molecules such as O 2 at room temperature or be etched away by CH 4. They can also develop into graphene flakes under controlled conditions: a temperature between 800 and 900 K and a suitable CH 4 pressure (10 –3–10 –1 mbar, depending on temperature). The growth rate of graphene is significantly restrained at higher CH 4 pressures, due to the accelerated etching of its carbon precursors. The identification of in operando carbon intermediates and the control of their evolution have great potential in designing heterogeneous catalysts for the direct conversion of methane. Finally, the observed carbon aggregation/etching equilibrium reveals an underlying mechanism in coking prevention and in the fabrication of large-area single-crystal graphene, where the suppression of seeding density and etching up of small grains are required.
ORCiD logo [1] ; ORCiD logo [2] ;  [3] ;  [3] ;  [3] ;  [1]
  1. National Univ. of Singapore (Suzhou) Research Inst., Suzhou (China); National Univ. of Singapore (Singapore)
  2. Brookhaven National Lab. (BNL), Upton, NY (United States)
  3. National Univ. of Singapore (Singapore)
Publication Date:
Report Number(s):
Journal ID: ISSN 2155-5435; R&D Project: 16068; KC0403020
Grant/Contract Number:
SC0012704; 91645102
Accepted Manuscript
Journal Name:
ACS Catalysis
Additional Journal Information:
Journal Volume: 7; Journal Issue: 9; Journal ID: ISSN 2155-5435
American Chemical Society (ACS)
Research Org:
National Univ. of Singapore (Singapore); National Univ. of Singapore (Suzhou) Research Inst., Suzhou (China); Brookhaven National Lab. (BNL), Upton, NY (United States)
Sponsoring Org:
USDOE; National Natural Science Foundation of China (NNSFC)
Country of Publication:
United States
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; carbon; catalyst; graphene; intermediate; methane; NAP-XPS; nickel
OSTI Identifier: