Single Mo₁(Cr₁) Atom on Nitrogen-Doped Graphene Enables Highly Selective Electroreduction of Nitrogen into Ammonia

Abstract

Searching for new types of electrocatalysts with high stability, activity, and selectivity is essential for the production of ammonia via electroreduction of nitrogen. Using density functional theory (DFT) calculations, we explore the stability of single metal atoms (M 1 ) supported on nitrogen-doped graphene (N 3 -G); the competitive adsorption of dinitrogen and hydrogen; and the potential competition of first dinitrogen protonation and hydrogen adsorption on metal sites. Consequently, we identify Mo 1 /N 3 -G and Cr 1 /N 3 -G as candidate electrocatalysts for nitrogen reduction reaction (NRR). The theoretically predicted selectivities (overpotentials) are 40% (0.34 V) and 100% (0.59 V) on Mo 1 /N 3 -G and Cr 1 /N 3 -G, respectively. The electroreduction of nitrogen proceeds via distal-toalternating hybrid mechanism with two spectator dinitrogen molecules. The high stability, high selectivity to ammonia, and relatively low overpotentials for NRR suggest Mo 1 (Cr 1 )/N 3 -G as the most promising electrocatalyst among those studied for electroreduction of nitrogen.

The FeN3 Doped Fluorographene for N2 Fixation: A Density Functional Theory Study

“…The charge distribution is in line with the selectivity of NRR versus HER. Being different from the TM screening, our results reveal the variation of the NRR performance is inherently originated from H/F decoration, highlighting the effect of substrate.…”

“…During the geometrical optimization, the systems are free to relax without any constraints. Since the same calculation settings have been adopted for the electrocatalysis stimulations, the selected parameters are reliable.…”

Electronic Structure Based Intuitive Design Principle of Single‐Atom Catalysts for Efficient Electrolytic Nitrogen Reduction

“…On various eNRR catalysts (bulk and SACs), the first step of proton abstraction by *N 2 intermediate has been found to be the PDS [6,27–29] . Therefore, in order to compare the eNRR activity among 13 SACs, we first compared the change in adsorption free energies between *N 2 and *N 2 H intermediates in the end‐on configurations, denoted by ΔG 1 =−(Δ −Δ ), as shown in Figure 2(a).…”

“…HER competes with eNRR at operating potentials due to easier reduction of proton itself to form H 2 gas, than utilization in six proton‐coupled electron transfer (PCET) steps of eNRR [29] . Therefore, we calculated ΔG *H on 13 TMs in ontop configuration for comparing HER activity, as shown in Figure 2(a).…”

Recent Advances in Noble‐Metal‐Free Catalysts for Electrocatalytic Synthesis of Ammonia under Ambient Conditions

“…With these advantages, single atom catalysts (SACs) have been exploited for the electrocatalytic NRR process and are expected to break up the stable N � N covalent triple bond with extremely high bond energy. [125] Based on DFT (Density functional theory), several single atom catalysts such as Mo 1 (Cr 1 ), [126] Cr, [127] W, [128] and Mo@BCN [129] are predicted as potential NRR electrocatalysts with high NH 3 yield rate and high Faradaic efficiency. However, these SACs are rarely reported in practice.…”