In situ modification of the d-band in the core–shell structure for efficient hydrogen storage via electrocatalytic N(2) fixation

The electrochemical N(2) reduction reaction (NRR) into NH(3), especially powered by clean and renewable electricity, is a promising alternative to the capital- and energy-intensive Haber–Bosch process. However, the inert N[triple bond, length as m-dash]N bond and the frantic competition of the hydrogen evolution reaction lead to a poor NH(3) yield rate and faradaic efficiency (FE). Here, we in situ construct a series of two-dimension core/shell V(2)O(3)/VN nanomeshes with a gradient nitride-layer thickness. Among them, V(2)O(3)/VN-2 exhibits the highest FE of 34.9%, an excellent NH(3) yield rate of 59.7 μg h(−1) mg(cat.)(−1), and outstanding cycle stability, exceeding those of most of the NRR electrocatalysts reported to date. First-principles calculations reveal that the d-band center of VN shifts up in a nearly linear manner with the decrease of nitride-layer thickness, and V(2)O(3)/VN-2 with a d-band center closer to the Fermi level can strengthen the d–2π* coupling between the catalyst and N(2) molecule, notably facilitating the N(2)-into-NH(3) conversion.