Catalytic Cu ₂ O/Cu Site Trades off the Coupling and Etching Reactions of Carbon Intermediates for CO ₂ ‐Assisted Graphene Synthesis

Abstract In the chemical vapor deposition (CVD) synthesis of graphene, the surficial chemical state of the metal substrate has exerted key roles in all elemental reaction steps determining the growth mechanism of graphene. Herein, a CO ₂ ‐participated annealing procedure is designed to construct catalytic Cu ₂ O/Cu sites on Cu foil for the graphene CVD synthesis with CO ₂ /CH ₄ as carbon sources. These Cu ₂ O/Cu species can catalyze the CH ₄ decomposition and subsequent C─C coupling to form C ₂ intermediates for fast growth of monolayer hexagonal graphene domains with a diameter of ≈30 µm within 0.5 min. The graphene growth kinetics can be bidirectionally regulated merely with the variation of CO ₂ flow rate during annealing and growth stages, in association with the Cu ⁺ /Cu ⁰ ratio, enabling simultaneous control over the size and shape of graphene domains. Density functional theory (DFT) calculations indicate that the catalytic Cu ₂ O/Cu sites reduce the activation energy by ≈0.13 eV for the first dehydrogenation of CH ₄ , allowing the growing rate of graphene driven by coupling of C ₂ intermediates faster than their etching rate by O‐containing ^* O and ^* OH species. The work provides novel insights into heterostructured nano‐catalyst consisting of zero valent metal and variably valent metal oxide that facilitate the controllable synthesis of graphene materials.