Nonoxidative Coupling of Methane over Ceria-Supported Single-Atom Pt Catalysts in DBD Plasma.

Plasma-catalytic direct nonoxidative coupling of methane (NCM) into C 2 hydrocarbons was investigated over ceria-supported atomically dispersed Pt (Pt/CeO 2 -SAC) and nanoparticle Pt (Pt/CeO 2 -NP) catalysts in dielectric barrier discharge (DBD) plasma. Nonthermal plasma facilitated C-H bond dissociation in CH 4 at low temperatures (<150 °C) and atmospheric pressure. The presence of Pt/CeO 2 catalysts in plasma further enhanced CH 4 conversion and C 2 hydrocarbon selectivity by enabling the conversion of vibrationally excited methane species with high internal energy on active Pt sites. Noticeably, the Pt/CeO 2 -SAC catalyst displayed a more remarkable performance, with a CH 4 conversion of 39% and a C 2 selectivity of 54% at 54 W. The enhanced CH 4 conversion was attributed to abundant coordinatively unsaturated Pt sites in Pt/CeO 2 -SAC, which were more active for C-H bond scission. Meanwhile, isolated Pt atoms in Pt/CeO 2 -SAC promoted C 2 hydrocarbon formation by hindering the unselective formation of coke from deep dehydrogenation of CH x • intermediates and higher hydrocarbons from oligomerization reactions.