Single Pd Atom–In₂O₃ Catalyzes Production of CH₃CH₂OH from Atom-Economic C–C Coupling of HCHO and CH₄

Abstract

Using methane as a reagent to synthesize high-value chemicals and high-energy density fuels through C−C coupling has attracted intense attention in recent decades, as it avoids completely breaking all C−H bonds in CH 4 . In the present study, we demonstrated that the coupling of HCHO with the CH 3 species from CH 4 activation to produce ethanol can be accomplished on the single Pd atom−In 2 O 3 catalyst based on the results of density functional theory (DFT) calculations. The results show that the supported single Pd atom stabilizes the CH 3 species following the activation of one C−H bond of CH 4 , while HCHO adsorbs on the neighboring In site. Facile C−C coupling of HCHO with the methyl species is achieved with an activation barrier of 0.56 eV. We further examined the C−C coupling on other single metal atoms, including Ni, Rh, Pt, and Ag, supported on In 2 O 3 by following a similar pathway and found that a balance of the three key steps for ethanol formation, i.e., CH 4 activation, C−C coupling, and ethoxy hydrogenation, was achieved on Pd/In 2 O 3 . Taking the production of acetaldehyde and ethylene on the Pd/In 2 O 3 catalyst into consideration, the DFT-based microkinetic analysis indicates that ethanol is the dominant product on the Pd/In 2 O 3 catalyst. The facile C−C coupling between HCHO and dissociated CH 4 makes formaldehyde a potential C1 source in the conversion and utilization of methane through an energy-and atom-efficient process.