Synergistic Effects of Crystal Phase and Strain for N 2 Dissociation on Ru(0001) Surfaces with Multilayered Hexagonal Close-Packed Structures.

The synergistic effects of strain and crystal phase on the reaction activity of nitrogen molecule dissociation have been studied using density functional theory calculations on Ru(0001) surfaces with multilayered hexagonal close-packed structures. The phase transformation from hexagonal close-packed phase (2H) to face-centered cubic (3C) phase or unconventional phases (4H, DHCP, 6H 1 , and 6H 2 ) would occur under the uniaxial tensile strain loaded along the c axis. The close-packed surfaces of unconventional crystal phases show an enhanced chemical reactivity for N adsorption due to the upshifted d -band center of Ru. However, the N 2 adsorption energy is almost independent of the applied strain and crystal phase. The optimized catalytic activity of Ru(0001) surfaces with the unconventional phases is found for the N 2 dissociation through breaking the scaling relationships between the reaction barrier and reaction energy. Our results indicate that the strain-induced phase transformation is an effective method to improve the catalytic activity of noble metal catalysts toward the N 2 dissociation reaction.