Single-Atom Mo Anchored on a Poly(heptazine imide) Nanosheet as a Novel Electrocatalyst Showing Excellent Behavior toward Nitrogen Reduction Reaction

Converting nitrogen into ammonia relying on the electrochemical nitrogen reduction reaction (NRR) is of great significance for sustaining life, and the development and screening of efficient electrocatalysts increasingly represent a major chemistry challenge. Herein, from density functional theory simulations, a series of recently developed poly(heptazine imide) (PHI)-anchored single-atom catalysts were investigated as the potential electrocatalysts for NRR, based on thermodynamics and kinetics analysis. The results reveal that the Mo-PHI nanosheet can effectively activate the inert N-2 and promote N-2 reduction to NH3 via the distal mechanism, which shows much better electrocatalytic activity than those of most ever-reported single-atom electrocatalysts, as reflected by the significantly much lower overpotential (0.05 V) and activation barrier (1.15 eV). The extraordinary activity of the Mo-PHI single layer is closely related to the efficient redistribution of electron density upon the adsorption of N-2 molecules, which can promote the electron transfer from the substrate to the electron acceptors, N-2. Moreover, the down-shift of projected density of states and the appropriately large d-band center (epsilon(d)) of the central Mo metal is beneficial to the N-2 adsorption for further reduction to generate NH3. Our predictions hence suggest the as-designed Mo-PHI single layer as a superior promising catalyst for efficient dinitrogen fixation and reduction.