Density Functional Theory Computation of Mo-adsorbed Two-dimensional Boron-nitrogen Monolayers for Nitrogen Reduction Reaction

doi:10.15541/jim20260021

Abstract

Abstract:

Electrocatalytic nitrogen reduction reaction (NRR) is regarded as a promising route for sustainable ammonia synthesis, but developing highly active and selective catalysts remains a critical challenge. In this work, the density functional theory calculations were performed to investigate the NRR performance of Mo-adsorbed B₂N, B₃N and B₄N monolayers. The strong interaction between Mo and its substrate ensures the good stability, as reflected by the binding energies of -8.39, -5.91 and -6.75 eV for Mo-adsorbed B₂N, B₃N and B₄N monolayers, respectively. The adsorbed Mo sites are able to activate the N₂ molecule, elongating the N≡N bond length from 1.108 Å in the gas phase to 1.128, 1.132 and 1.132 Å on Mo-B₂N, Mo-B₃N and Mo-B₄N, respectively. Free energy profile analysis reveals that the thermodynamic barriers are 1.21, 1.07 and 0.61 eV for Mo-B₂N, Mo-B₃N and Mo-B₄N, with Mo-B₄N exhibiting the highest activity. This trend clearly demonstrates that the Mo reactivity is well-tuned by its coordination. Furthermore, the electronic structure analysis shows a relation between the strength of N≡N bond and the thermodynamic energy, where a weaker strength of N≡N bond indicates a better NRR activity. Mo-B₄N material also exhibits a high thermodynamic stability, as reflected by the robustness of the structural rigidity wherein no structural collapse is observed under the room temperature of 300 K. Therefore, Mo-B₄N is expected to be an active and durable catalyst for the NRR. This study provides theoretical guidance for the design of NRR electrocatalysts and proposes viable candidate systems for experimental synthesis. The datasets in this article are listed in Science Data Bank at https://www.doi.org/10.57760/sciencedb.jim.00043.

Key words: nitrogen reduction reaction, density functional theory, single-atom catalysis

CLC Number:

TQ174

LI Zhi, ZHANG Junmiao, FENG Ziyang, XIAO Beibei, SONG Erhong. Density Functional Theory Computation of Mo-adsorbed Two-dimensional Boron-nitrogen Monolayers for Nitrogen Reduction Reaction[J]. Journal of Inorganic Materials, 2026, 41(10): 1517-1524.

Figures/Tables 10

Fig. 1 (a) Model structures; (b) Linear relationship between d-band center and binding energy; (c) Iso-surface plots of the charge density difference (CDD) and charge transfer quantities; (d) Partial density of states (PDOS) analysis for Mo interacting with B2N, B3N and B4N substrates, respectively, with the p-band contributions from B2N, B3N and B4N represented the combined p-bands of B and N atoms directly bonded to metal atoms in each structure

Fig. 2 (a) Adsorption free energies of N2 under two adsorption configurations; (b) PDOS of Mo with N2 adsorbate; (c) Charge transfer quantity for N2 adsorbed on Mo-B4N; (d) Crystal orbital Hamilton population (COHP) analysis of N≡N bond in adsorbed *N2

Table 1 Free energy changes ΔG of elementary steps and thermodynamic barriers ΔGmax

Structure	Mechanism	ΔG/eV						ΔG_max/eV
Mo-B₂N	Distal	1.21	−0.32	−0.19	−0.44	−0.01	−0.90	1.21
	Alternating	1.21	0.08	−0.07	1.25	−2.29	−0.82	1.25
	Enzymatic	1.75	−0.43	−0.65	−0.67	−0.01	−0.50	1.75
Mo-B₃N	Distal	1.07	0.48	−0.76	−0.74	0.53	−0.12	1.07
	Alternating	1.07	1.23	−1.28	0.44	−1.71	0.70	1.23
	Enzymatic	0.64	−0.03	−0.65	−1.51	−0.32	1.34	1.34
Mo-B₄N	Distal	0.61	−0.04	−0.01	−0.74	−0.51	0.13	0.61
	Alternating	0.61	0.63	−0.88	0.82	−2.35	0.61	0.82
	Enzymatic	0.98	−0.07	−0.63	−1.33	−0.34	0.66	0.98

Fig. 3 (a) Distal pathway of Mo-B4N; (b) Alternating pathway of Mo-B4N; (c) Enzymatic pathway of Mo-B4N; (d) Thermodynamic barriers of Mo-B2N, Mo-B3N and Mo-B4N

Fig. 4 (a) Total density of states (TDOS) of Mo-B4N with varied N-containing intermediates along the distal pathway; (b) Linear relationship between -ICOHP of N≡N bond and thermodynamic energy barrier; (c) Bond lengths of N-N and Mo-N; (d) AIMD simulation of Mo-B4N at room temperature of 300 K

Table 2 Bond length between Mo and B/N atom

Time/ps		0	1	2	3	4	5	6	7	8	9	10
Bond length/Å	Mo-B1	2.325	2.270	2.210	2.258	2.368	2.321	2.317	2.342	2.198	2.298	2.242
	Mo-B2	2.209	2.141	2.174	2.211	2.194	2.215	2.267	2.148	2.161	2.162	2.325
	Mo-B3	2.249	2.245	2.209	2.317	2.148	2.277	2.239	2.204	2.261	2.181	2.257
	Mo-B4	2.029	2.048	2.030	2.023	2.017	2.048	2.006	2.043	2.069	2.004	2.091
	Mo-B5	2.081	2.087	2.178	2.179	2.111	2.053	2.082	2.084	2.188	2.089	2.102
	Mo-N	2.236	2.169	2.251	2.222	2.247	2.206	2.266	2.389	2.149	2.141	2.217

Table S1 Comparison of adsorption energies with and without vdW corrections

Energy	NN	NNH	NNH₂	N	NH	NH₂	NH₃
With corrections/eV	−1.235	−2.925	−3.920	−8.270	−5.318	−4.230	−1.882
Without corrections/eV	−1.139	−2.820	−3.789	−8.232	−5.251	−4.133	−1.779
Difference/eV	−0.096	−0.105	−0.131	−0.038	−0.067	−0.097	−0.103

Table S2 Comparison of ΔGmax cited from the previous reports

Catalyst	ΔG_max/eV	Ref.
Mo-B₄N	0.61	This work
Mo₃(HAB)₂	0.66	[11]
Mo-C₄N₃	0.76	[13]
MoPc-TFPN	0.21	[15]
Mo-C₃N₃	0.41	[14]
Mo-BN	1.01	[12]
Mo-GR	0.71	[12]
Mo-GDY	0.43	[12]
Mo-C₉N₄	0.40	[26]

Fig. S1 Free energies of hydrogen adsorption ΔGH under different potentials

Fig. S2 Labeled coordination environment of Mo-B4

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