Theoretical study on the reaction mechanism of carbon dioxide reforming of methane on La and La2O3 modified Ni(1 1 1) surface

Abstract

The carbon dioxide (dry) reforming of methane (DRM) (CH4 + CO2 → 2CO + 2H2) on La and La2O3 modified Ni(1 1 1) has been investigated theoretically. As promoters, La and La2O3 strengthen the adsorption of the intermediates compared with pure Ni(1 1 1). The strong adsorption of CO2 on La2O3 modified Ni(1 1 1) deforms La2O3, and the complex intermediate CO2(La2O2-O) is formed. The CO2(La2O2-O) participates in the DRM reaction and reduces the carbon deposition on the catalyst surface. For La and La2O3 modified Ni(1 1 1), the reactions of CH4 + CO2 → CH + 3H + CO + O → CHO + 3H + CO → 2CO + 2H2 and CH4 + CO2 + La2O3 → CH + CO2(La2O2-O) + 3H → CHO + CO2(La2O2) + 3H → 2CO + 2H2 + La2O3 are the most favorable pathways for DRM, respectively. Both the density functional study and microkinetic analysis support that compared with pure Ni(1 1 1), La and La2O3 modified Ni(1 1 1) improve the reaction both thermodynamically and kinetically. The carbon deposition is suppressed on La2O3 modified Ni(1 1 1) due to the lower rate in the reaction CH → C + H, compared with La modified Ni(1 1 1).