Extended Data Fig. 2: DFT calculation results.
From: Vacancy-enabled N2 activation for ammonia synthesis on an Ni-loaded catalyst
a, Calculated projected DOS of Ni8/La32N32, with detailed atomic configuration. The Ni[1], La[2], N[2] and N[1] atoms are emphasized using dashed lines. Substantial overlapping of the projected DOS of Ni (Ni[1]) and the nearest N (N[2]), observed at around −4 eV < E − EF < −2 eV, is much more stable than the interaction between Ni (Ni[1]) and the second-nearest N (N[1]). b, Proposed reaction barriers for N2 dissociation on VN sites of the Ni-loaded LaN surface. In scenario I, two N2 molecules are activated at two adjacent VN sites in the initial step (IS), and the two dissociated top N atoms combine to form a new N2 molecule with a barrier of 2.46 eV in the final step (FS). In scenario II, a N2 molecule is activated at the VN site (IS) and the dissociated top N atom is transferred to an adjacent Nlattice site with a hopping barrier of 3.34 eV (FS). c, Proposed reaction mechanism for N2 dissociation on Ni(111) surface. Owing to the extremely weak interaction between N2 and Ni, the adsorption energy is nearly 0.00 eV and the reaction barrier for the dissociation of N2 is calculated to be 1.55 eV. The structures of intermediates and transition states (TSs) for the key elementary steps are shown in the reaction paths. d, The Ni8/La32N31 model and ENV at different N sites.
