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Lu et al. J Mater Inf 2024;4:31 https://dx.doi.org/10.20517/jmi.2024.65 Page 5 of 16

Figure 1. (A) Top and side views of the optimized structure of TM@C N-NCM. TM, C, and N atoms are represented in grey, yellow, and
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blue, respectively; (B) The 3d, 4d, and 5d transition metals selected for this study; (C) Calculated binding energies (E ) of the TMs on
b
the C N-NCM substrate. TM@C N-NCM:Transition metals into a two-dimensional C N-based nanomaterial; TM: Transition metals.
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Screening strategy
As shown in Figure 2, the NRR proceeds through several mechanistic pathways, including Distal,
Alternating, Enzymatic, and Consecutive routes, each involving different proton and electron transfer
sequences. Given this complexity, a systematic and efficient screening approach is essential for evaluating
the catalytic performance of the designed catalysts. A three-step screening strategy was developed based on
previous theoretical studies [38,71,72] . The first criterion is the E of N , as effective N binding is crucial for
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ads
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initiating NRR. A threshold of E < -0.50 eV was established to ensure strong chemisorption. Although the
ads
pathways differ in intermediates, two protonation steps are critical across all mechanisms: the first
protonation (*N + H + e = *NNH), which breaks the N≡N triple bond, and the last protonation step
+
-
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-
(*NH + H + e = *NH ), where nitrogen transitions from a half-filled sp hybrid orbital in *NH to a fully
+
3
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3
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filled sp configuration in NH . These two steps have been widely recognized in previous studies as the most
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likely potential-determining steps (PDS) in NRR, primarily due to the significant energy barriers associated
with them [73-77] . Thus, the second and third criteria focus on the ΔG for these protonation steps, with ΔG <
0.55 eV as the criterion for efficient catalysis. By applying these three criteria, i.e., favorable N adsorption
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and ΔG for the first and last protonation steps, we systematically screened 27 SACs, identifying the most
promising candidates for efficient NRR in the following.
N adsorption and activation
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The adsorption of N on TM@C N-NCM occurs in two primary configurations, i.e., end-on and side-on.
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The corresponding E and N-N bond lengths for both configurations are summarized in Figure 3, with
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detailed values provided in Supplementary Table 1. Among the 27 investigated TMs, Zn, Ru, Cd, and Hg
can only stabilize N in the end-on configuration, while the remaining metals can accommodate both
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adsorption modes. The E values for the end-on configuration range from -1.35 eV to -0.15 eV, while those
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for the side-on configuration range from -1.44 eV to -0.19 eV. More negative E values indicate stronger N
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binding, suggesting that the N molecule preferentially adopts the end-on configuration for most TMs. The
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N-N bond lengths after adsorption vary between 1.10 Å and 1.19 Å, indicative of varying degrees of N
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