Promotional effect of alkaline earth over Ni–La2O3 catalyst for CO2 reforming of CH4: Role of surface oxygen species on H2 production and carbon suppression

Alkaline earth elements (Mg, Ca and Sr) on Ni–La2O3 catalyst have been investigated as promoters for syngas production from dry CO2 reforming of methane (DRM). The catalysis results of DRM performance at 600 °C show that the Sr-doped Ni–La2O3 catalyst not only yields the highest CH4 and CO2 conversions (∼78% and ∼60%) and highest H2 production (∼42% by vol.) but also has the lowest carbon deposition over the catalyst surface. The XPS, O2-TPD, H2-TPR and FTIR results show that the excellent performance over the Sr-doped Ni–La2O3 catalyst is attributed to the presence of a high amount of lattice oxygen surface species which promotes C–H activation in DRM reaction, resulting in high H2 production. Moreover, these surface oxygen species on the Ni-SDL catalyst can adsorb CO2 molecules to form bidentate carbonate species, which can then react with the surface carbon species formed during DRM, resulting in higher CO2 conversion and lower carbon formation.