Weakening the intramolecular N-N bond is essential to promote direct hydrogenation of adsorbed N2 on catalyst surfaces. The interaction of N2 with Li on Ni{110} surfaces has been investigated. We show that the N-N bond is significantly weakened with increasing Li coverage, evidenced by large redshifts in N-N stretch frequency of up to 380 cm(-1) compared to the gas phase. Some increased thermal stability of the most weakened N2,ads states is also observed. We speculate that the various observed redshifts in N-N stretch frequency are associated with an enhanced backfilling of the 2π* antibonding orbital of N2 due to both the Li-induced surface electrostatic field, and the formation of Lix(N2)y surface complexes.
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