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

The carbon dioxide (dry) reforming of methane (DRM) (CH 4  + CO 2  → 2CO + 2H 2 ) on La and La 2 O 3 modified Ni(1 1 1) has been investigated theoretically. As promoters, La and La 2 O 3 strengthen the adsorption of the intermediates compared with pure Ni(1 1 1). The strong adsorption of CO 2 on La 2 O 3 modified Ni(1 1 1) deforms La 2 O 3 , and the complex intermediate CO 2 (La 2 O 2 -O) is formed. The CO 2 (La 2 O 2 -O) participates in the DRM reaction and reduces the carbon deposition on the catalyst surface. For La and La 2 O 3 modified Ni(1 1 1), the reactions of CH 4  + CO 2  → CH + 3H + CO + O → CHO + 3H + CO → 2CO + 2H 2 and CH 4  + CO 2  + La 2 O 3  → CH + CO 2 (La 2 O 2 -O) + 3H → CHO + CO 2 (La 2 O 2 ) + 3H → 2CO + 2H 2  + La 2 O 3 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 La 2 O 3 modified Ni(1 1 1) improve the reaction both thermodynamically and kinetically. The carbon deposition is suppressed on La 2 O 3 modified Ni(1 1 1) due to the lower rate in the reaction CH → C + H, compared with La modified Ni(1 1 1). [ABSTRACT FROM AUTHOR]