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

The electrochemical N2 reduction reaction (NRR) into NH3, especially powered by clean and renewable electricity, is a promising alternative to the capital- and energy-intensive Haber–Bosch process. However, the inert N <svg xmlns="http://www.w3.org/2000/svg" version="1.0" width="23.636364pt" height="16.000000pt" viewBox="0 0 23.636364 16.000000" preserveAspectRatio="xMidYMid meet"><metadata> Created by potrace 1.16, written by Peter Selinger 2001-2019 </metadata><g transform="translate(1.000000,15.000000) scale(0.015909,-0.015909)" fill="currentColor" stroke="none"><path d="M80 600 l0 -40 600 0 600 0 0 40 0 40 -600 0 -600 0 0 -40z M80 440 l0 -40 600 0 600 0 0 40 0 40 -600 0 -600 0 0 -40z M80 280 l0 -40 600 0 600 0 0 40 0 40 -600 0 -600 0 0 -40z"/></g></svg> N bond and the frantic competition of the hydrogen evolution reaction lead to a poor NH3 yield rate and faradaic efficiency (FE). Here, we in situ construct a series of two-dimension core/shell V2O3/VN nanomeshes with a gradient nitride-layer thickness. Among them, V2O3/VN-2 exhibits the highest FE of 34.9%, an excellent NH3 yield rate of 59.7 μg h−1 mgcat.−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 V2O3/VN-2 with a d-band center closer to the Fermi level can strengthen the d–2π* coupling between the catalyst and N2 molecule, notably facilitating the N2-into-NH3 conversion.