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Meng et al. J. Mater. Inf. 2025, 5, 3 https://dx.doi.org/10.20517/jmi.2024.74 Page 17 of 25

energy generally exhibit lower U , making adsorption energy a simple and effective descriptor.
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Chen et al. demonstrated that the NRR activity of TM/MoS catalysts is affected by the d-orbital electron
2
[121]
density states at the E , with N adsorption inversely proportional to the U value . Similarly, Ma et al.
F
2
L
investigated the activity of TM (TM = Mn, Fe, Co, Ni)-based SACs/DACs/TACs on GDY, finding an
approximate linear relationship between the adsorption energy of N and U L [122] .
*
Considering that the formation of N H is the potential determining step, Ren et al. examined the scaling
*
2
relation between the adsorption energy of N H and U , concluding that Nb atoms supported on g-C N are
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3
4
2
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particularly promising NRR catalysts due to their low U and strong N H adsorption . Luo et al. further
[123]
*
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observed that N H and NH adsorption energies are proportional to ∆E( N) on TM-modified Co clusters
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*
*
4
2
2
supported on GDY, revealing the scaling relationship among the adsorbed N H species. They concluded
x
y
that tightly bound N atoms hinder NH formation, while loosely bound N atoms impede protonation of N
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2
3
to N H. The results showed that the NRR activity of TM/g-CN catalyst can be well estimated by the
*
2
adsorption energy of N .
[124]
*
Collectively, these findings suggest that adsorption energy is a useful descriptor for estimating NRR activity,
despite its limitation as a theoretical measure that lacks experimental control.
Electronic descriptors
The degree of electronic coupling between adsorbed intermediates and the catalyst also plays a central role
in catalytic activity . The crystal orbital Hamilton population (COHP) method, grounded in DFT
[116]
calculations, provides a powerful tool for analyzing the electronic structure of chemical bonds within a
crystal. Specifically, it characterizes the bonding and antibonding interactions between atoms. Its integrated
counterpart, the integrated COHP (ICOHP), aggregates COHP values over a defined energy range,
capturing both bonding and antibonding contributions to offer a holistic measure of bond strength. In
NRR, COHP and ICOHP are commonly used to assess bonding and antibonding populations and the
interactions between the catalyst and NRR intermediates. These tools provide critical insights into the
formation and cleavage of chemical bonds during the reaction, deepening our understanding of the origins
of NRR activity.
As shown in Figure 10A, interactions between various TM centers and NRR intermediates can be
categorized into bonding states below the E and antibonding states above E . These unique properties make
F
F
COHP a powerful and effective electronic descriptor for evaluating catalytic performance.
Through an ICOHP analysis, Niu et al. examined the bonding and antibonding states of N H intermediates
y
x
*
2
adsorbed on TM/g-CN, finding a strong linear correlation (R = 0.84) between ICOHP and N adsorption
energy [Figure 10B] . Similarly, Liu et al. applied ICOHP analysis to assess the NRR performance of
[42]
TM@N -G and TM@g-C N, revealing a good linear relationship between ICOHP and ΔG N2-NNH (R = 0.88
2
2
6
and 0.99, respectively) [Figure 10C and D] . These results indicate that ICOHP is a promising descriptor
[125]
to describe the NRR activity of SACs and SCCs.
In addition to ICOHP, other electronic properties, particularly spin magnetic moment, have been explored
as descriptors for NRR. Wang et al. investigated the catalytic activity of SACs on 2D VSe , finding that the
2
U for NRR is linked to the total magnetic moment of TM-VSe 2 [126] . Zhang et al. further studied dual single-
L
atom sites, discovering that the metal atoms located in adjacent vacancies can regulate the spin magnetic
moment of the active Fe atoms despite a large distance, thereby enhancing N activation and reduction .
[127]
2