In situ generation of active motifs on Ni/Al2O3 during partial oxidation of methane to syngas

Abstract The active phase for the partial oxidation of methane (POM) to syngas on Ni catalysts has been attributed to metallic nanoparticles, with high Ni loadings (~10 wt%) considered essential. Here we show, on NiO surfaces, that in situ-generated [Ni 1 O 1 Ni 4 ] motifs, where one Ni atom sits on an oxygen atom that bridges four surrounding Ni atoms, drive POM with promising efficiency. A Ni/Al 2 O 3 -ME catalyst with Ni loading of 0.8 wt% fabricated via deposition of preformed Ni nanoparticles onto Al 2 O 3 achieves 92.0% CH 4 conversion and 87.0% CO/H 2 selectivity at 650 °C for POM, maintaining a stable H 2 /CO ratio of 2.0. Operando spectroscopy and environmental microscopy confirm the oxidation of metallic Ni to NiO during POM. The results of operando high-resolution annular bright-field imaging, combined with density functional theory calculations, suggest that the [Ni 1 O 1 Ni 4 ] structure formed on the NiO(100) surface reduces the C–H activation barrier to 12.5 kcal mol −1 . Thus, metallic Ni nanoparticles with high metal loadings may not be strictly required for efficient POM.