Nitrogen Reduction Research Articles

Molybdenum carbide nanosheets with iron doping as electrocatalysts for highly efficient ammonia electrosynthesis

The electrochemical reduction of nitrogen to ammonia represents a greener alternative to the Haber-Bosch process, demanding a shift towards low-cost and high-efficiency electrocatalysts. Recent advances in research have demonstrated the potential of molybdenum carbide-based catalysts to have their unique electronic structure and physicochemical properties. This study introduces ultrathin iron-doped molybdenum carbide nanosheets (Fe-MoC) as a novel catalyst for ammonia electrosynthesis. Demonstrating a remarkable ammonia production rate of 16 µg h−1 mg−1 and a Faradaic efficiency (FE) of approximately 13 % at −0.2 V, our synthesized Fe-MoC nanosheets stand out for their superior catalytic activity and selectivity towards nitrogen activation. The indophenol technique was employed to identify the generation of NH3 in our experiments, followed by UV–vis spectrometry for quantitative analysis. Additionally, various characterization techniques, including XRD, Raman, and XPS, were used to analyze the material structure and surface properties. Through comprehensive characterization and electrochemical studies, we reveal the pivotal role of iron doping in enhancing the electrocatalytic performance for nitrogen reduction reaction (NRR), offering insights into the mechanistic pathways facilitated by Fe-MoC. The future development and perspective of Fe-MoC towards high performance are proposed.

The first principles study of the dual-atom catalyst based on g-C3N5 for efficient nitrogen fixation

Electrocatalytic nitrogen reduction reaction (NRR) for ammonia production has broad prospects because of its mild green reaction conditions. However, the available catalysts cannot meet the needs of industrial ammonia production due to low catalytic activity and poor selectivity. In our work, the dual-atom catalysts (DAC) supported by g-C3N5 with transition metals dual-atom were designed based on the first principles calculation. Based on the criteria of stability, catalytic activity, and the competitive landscape between NRR and hydrogen evolution reaction (HER), the Ni2/g-C3N5 stands out as the most promising candidate among 30 designed diatomic catalysts for NRR, exhibiting remarkable potential for this reaction. In fact, the Ni2/g-C3N5 possesses low limiting potential (−0.27 V) and its selectivity of NRR is nearly 100 %. Importantly, by comprehensively considering the pivotal parameters of charge order, electronegativity, and d-band center, a dedicated descriptive descriptor has been formulated. This result not only profoundly uncovers the intrinsic origins of catalytic activity in the NRR but also significantly expedites the screening process for highly efficient catalysts. Our work not only accelerates the search for an NRR catalyst with high activity but also provides theoretical guidance for subsequent experiments on DACs.

Valence electron matching law for MXene-based single-atom catalysts

Single-atom catalysts (SACs) have attracted considerable interest in the fields of energy and environmental science due to their adjustable catalytic activity. In this study, we investigated the matching of valence electron numbers between single atoms and adsorbed intermediates (O, N, C, and H) in MXene-anchored SACs (M-Ti2C/M-Ti2CO2). The density functional theory results demonstrated that the sum of the valence electron number (VM) of the interface-doped metal and the valence electron number (VA) of the adsorbed intermediates in M-Ti2C followed the 10-valence electron matching law. Furthermore, based on the 10-valence electron matching law, we deduced that the sum of the valence electron number (k) and VM for the molecular adsorption intermediate interactions in M-Ti2CO2 adhered to the 11-valence electron matching law. Electrostatic repulsion between the interface electrons in M-Ti2CO2 and H2O weakened the adsorption of intermediates. Furthermore, we applied the 11-valence electron matching law to guide the design of catalysts for nitrogen reduction reaction, specifically for N2→NNH conversion, in the M-Ti2CO2 structure. The sure independence screening and sparsifying operator algorithm was used to fit a simple three-dimensional descriptor of the adsorbate (R2 up to 0.970) for catalyst design. Our study introduced a valence electron matching principle between doped metals (single atoms) and adsorbed intermediates (atomic and molecular) for MXene-based catalysts, providing new insights into the design of high-performance SACs.

Theoretical insights into efficient electrocatalysts for nitrogen reduction reaction by transition metal atoms supported on g-C3N4

NH3 is considered one of the most important chemicals, not only as an industrial feedstock for the production of fertilizers, but also as renewable carbon-free energy carrier. In recent years, electrocatalytic nitrogen reduction reaction (NRR), which uses N2 and H2O as raw materials to synthesize NH3, is considered as one of the most promising methods for N2 fixation. Therefore, the design and synthesis of NRR electrocatalysts with high catalytic performance is very important. Herein, using density functional theory method, 3d transition metal single atom anchored to g-C3N4 as single-atom catalysts was studied for the catalytic reduction of N2. The results found that V@g-C3N4 exhibited high electrocatalytic activity and good catalytic selectivity. The limiting potential was only –0.115 V. Furthermore, the relevant electronic properties of V@g-C3N4 were also analyzed. Our work can provide ideas and help to understand the reaction mechanism of single atom doped g-C3N4 as NRR electrocatalysts with excellent catalytic performance.

Revolutionizing Nitrogen Electrocatalysis: Atomically Dispersed Ruthenium Catalyzed by Manganese for Unmatched Performance

Seeking sustainable ammonia, the electrocatalytic nitrogen reduction reaction (NRR) via electrocatalysis is crucial but challenged by catalyst efficiency and stability needs. This study presents RuMn-NC@NF, a novel bimetallic ruthenium-manganese catalyst synthesized via chemical vapor deposition (CVD), featuring atomically dispersed active sites on porous carbon. The strategic incorporation of manganese into the ruthenium lattice modulates the electronic structure, optimizing nitrogen adsorption and accelerating reaction kinetics. Our results demonstrate that RuMn-NC@NF achieves a remarkable Faradaic efficiency of 33.37% and an ammonia yield rate of 187.06μgh-1 mgcat.-1. XRD, SEM, HAADF-STEM, and XPS characterizations affirm the atomic distribution and elemental makeup of the catalyst. Meanwhile, DEMS and DFT calculations reveal the intrinsic mechanisms driving the reaction. The RuMn-NC@NF catalyst exhibits excellent stability over multiple cycles, underscoring its potential for practical and sustainable ammonia production. This research advances electrocatalysis with an innovative NRR catalyst for sustainable applications.

Oxygen vacancy-rich Fe2O3/Co3O4 heterostructure electrocatalyst promotes N2 activation for efficient nitrogen reduction

The adsorption and activation of N2 as well as the competitive hydrogen evolution reaction (HER) pose significant challenges to the electrocatalytic nitrogen reduction reaction (ENRR), which severely limits its industrial application. Therefore, exploring the ENRR electrocatalysts with high activity and selectivity is an extremely important task. In this work, the oxygen vacancy-rich Fe2O3/Co3O4 heterostructures (referred to as Vo-X-Fe2O3/Co3O4) were rationally designed by employing Co3O4 as a template via a simple hydrothermal and subsequent calcination method, which acted as highly efficient ENRR electrocatalysts. The electrocatalytic activity of Vo-X-Fe2O3/Co3O4 can be easily regulated by optimization of the Fe content and the introduction of oxygen vacancy (Vo). The results demonstrate that the optimized Vo-1.0-Fe2O3/Co3O4 catalyst achieves a high NH3 yield of 47.37μgh-1 mgcat-1 and a Faradaic efficiency (FE) of 22.42%. Moreover, the excellent stability and reproducibility are also demonstrated. The comprehensive characterizations reveal that the exceptional performance of Vo-1.0-Fe2O3/Co3O4 can be attributed to the improved N2 adsorption and activation, restricted competitive HER and promoted electron transfer kinetics induced by the synergistic introduction of Vo and Fe. This work emerged a new speculating orientation for rational design of ENRR catalysts.

Enhanced ammonia yield rate from nitrogen on collapsed dodecahedral-shaped Co/NC electrocatalyst

Nowadays, multi-component non-precious metal catalysts have been considered as a significant strategy for enhancing the yield of synthesizing NH3 by electrocatalytic nitrogen reduction reaction (E-NRR). In the present work, carbon composites doped with well-dispersed Co and N (Co/NC) were prepared by pyrolyzing zeolitic imidazolate framework-67 (ZIF-67) at various temperatures protected under a N2 flow. Co/NC exhibits a collapsed dodecahedral morphology with a mesoporous structure (3.5-4 nm). The chemical states of Co/N and the structural defects of C are closely related to the carbonization temperature. In a N2-saturated 0.1 M KOH electrolyte, the as-prepared catalysts exhibit an NH3 yield rate (Y(NH3)) of 60.57 μg h-1 mgcat.-1 and a Faradaic efficiency (FE) of 23.3% at -0.1 V (vs the reversible hydrogen electrode, RHE) at ambient conditions. The enhanced E-NRR activity of Co/NC may primarily originate from an associative distal pathway on the Co-N3-C sites and the carbon defects in an alkaline electrolyte. Specifically, this work presents a three-component E-NRR catalyst with excellent stability and great activity based on Co/NC.

Coordination Structure Modulation in Group-VIB Metal Doped Ag3PO4 Augments Active Site Density for Electrocatalytic Conversion of N2 to NH3.

Doping is considered a promising material engineering strategy in electrochemical nitrogen reduction reaction (NRR), provided the role of the active site is rightly identified. This work concerns the doping of group VIB metal in Ag3PO4 to enhance the active site density, accompanied by d-p orbital mixing at the active site/N2 interface. Doping induces compressive strain in the Ag3PO4 lattice and inherently accompanies vacancy generation, the latter is quantified with positron annihilation lifetime studies (PALS). This eventually alters the metal d-electronic states relative to Fermi level and manipulate the active sites for NRR resulting into side-on N2 adsorption at the interface. The charge density deployment reveals Mo as the most efficient dopant, attaining a minimum NRR overpotential, as confirmed by the detailed kinetic study with the rotating ring disk electrode (RRDE) technique. In fact, the Pt ring of RRDE fails to detect N2H4, which is formed as a stable intermediate on the electrode surface, as identified from in-situ attenuated total reflectance-infrared (ATR-IR) spectroscopy. This advocates the complete conversion of N2 to NH3 on Mo/Ag3PO4-10 and the so-formed oxygen vacancies formed during doping act as proton scavengers suppressing hydrogen evolution reaction resulting into a Faradaic efficiency of 54.8% for NRR.

Computational Insight into Transition Metal Atoms Anchored on B2C3P as Single‐Atom Electrocatalysts for Nitrogen Reduction Reaction

AbstractNH3 is not only an important chemical raw material but also a high‐energy storage chemical with zero carbon. Electrocatalytic nitrogen reduction reaction (NRR), which can be driven by clean electric energy under ambient conditions, has become a promising technology for NH3 synthesis due to its environmentally friendly properties. Because of the limitations of low yield and high overpotential, efficient catalysts are urgently needed to solve this problem. In this study, based on density functional theory method and high throughput screening strategy, the NRR was investigated on transition metal single atom anchored to 2D B2C3P surface (TM@B2C3P) as single‐atom catalysts (SACs). The results showed that V@B2C3P and Ti@B2C3P have good catalytic properties, and the limiting potentials were −0.10 and −0.24 V, respectively. Furthermore, the charge density difference and crystal orbital Hamilton population calculations demonstrated that the high catalytic activity can be attributed to the obvious charge transfer between TM@B2C3P and the adsorption intermediates. It is hoped that this work can play a certain role in exploring the application of SACs in NRR.

Tailoring the d-Band Center of WS2 by Metal and Nonmetal Dual-Doping for Enhanced Electrocatalytic Nitrogen Reduction.

Tuning the adsorption energy of nitrogen intermediates and lowering the reaction energy barrier is essential to accelerate the kinetics of nitrogen reduction reaction (NRR), yet remains a great challenge. Herein, the electronic structure of WS2 is tailored based on a metal and nonmetal dual-doping strategy (denoted Fe, F-WS2) to lower the d-band center of W in order to optimize the adsorption of nitrogen intermediates. The obtained Fe, F-WS2 nanosheet catalyst presents a high Faradic efficiency (FE) of 22.42% with a NH3 yield rate of 91.46µg h-1 mgcat. -1. The in situ characterizations and DFT simulations consistently show the enhanced activity is attributed to the downshift of the d-band center, which contributes to the rate-determining step of the second protonation to form N2H2 * key intermediates, thereby boosting the overall nitrogen electrocatalysis reaction kinetics. This work opens a new avenue to enhanced electrocatalysis by modulating the electronic structure and surrounding microenvironment of the catalytic metal centers.

Scalable ammonia synthesis on the modified crystal structure of Cu3PS4 electrocatalyst

Ammonia production, which is vital for agricultural and industrial applications, typically relies on energy-intensive processes that contribute to global CO2 emissions. Electrochemical nitrogen reduction is a promising alternative, although it faces challenges such as low yield and selectivity. Transition-metal-based catalysts, particularly Cu, are promising for overcoming these limitations. Cu3PS4 catalysts were synthesized and evaluated using a 9 cm2-scale electrode, revealing enhanced performance attributed to change in the crystal and electronic structure of Cu, facilitating N2 adsorption and improving the reaction activity. Notably, the ammonia synthesis rate reached 128 μg h-1 mgcat-1 at −1.0 V vs. RHE and faradaic efficiency was 34 % at −0.8 V vs. RHE. These findings provide potential insights into the improvement of practical electrochemical synthesis of ammonia.

The role of Aspergillus flavus in modulating the physiological adjustments of sunflower to elevated CO2 and temperature

Exploring the interactions between plants and foliar endophytic fungi under varying climatic conditions is crucial for harnessing endophytes that enhance plant resilience to environmental stressors. This study examines the role of a specific strain of Aspergillus flavus as an endophyte in sunflowers under standard and altered CO2 and temperature regimes. We assessed the impact of this fungus on physiological traits such as chlorophyll and flavonoid content, gas exchange, and Chlorophyll a fluorescence using open-top chambers simulating ambient (∼420 µmol mol−1) and elevated (∼880 µmol mol−1) CO2 levels, along with a temperature increase of 3°C. The findings indicate that A. flavus promotes nitrogen assimilation and chlorophyll production under ambient conditions, potentially enhancing sunflower growth and photosynthetic performance. However, under elevated temperatures (eT), inoculation with A. flavus resulted in decreased biomass and reduced Photosystem II efficiency. Elevated CO2 (eCO2) conditions also led to unexpected negative effects, with reductions in foliar nitrogen, leaf area, and light capture efficiency, culminating in diminished biomass. When both elevated CO2 and temperature conditions were combined (eCO2eT), the interaction further impaired Photosystem II efficiency, suggesting exacerbated physiological stress. These results demonstrate that environmental modifications can transform A. flavus from a beneficial endophyte to a potential pathogen, highlighting the dual nature of plant-fungal interactions. This study underscores the complexity of these relationships under changing climatic conditions and suggests a cautious approach to the agricultural use of endophytes to ensure plant health and productivity.

The active site of Mδ+ tailed by B (or N)-doped graphyne for nitrogen reduction reaction through DFT study

NN bond activation is one of the technical problems in the conversion of N2-to-NH3. In this work, we researched Cr, Mn, Co, Ni, Cu and Pt metal single atoms anchored on B/N-doped graphyne (M/X-GY) catalysts systematically by means of DFT. The results of Bader charge and charge density verified the charge transfers between single metal and the doped graphyne in M/X-GY catalysts. Cr (+1.001 e) and Mn (+0.800 e) exhibit higher positive valence, which is favorable for N2 adsorption. Based on the "donation and back-donation" mechanism, the energies gaps of 5σ-N2 and d-M for M=Cr, Mn and Co have the lower values of 3.01, 3.18, 3.18 eV, respectively, and the N2 adsorption energies on Cr/GY (−2.046 eV) and Mn/GY (−1.622 eV) have the more negative values. As a result, the catalyst of Cr metal atom anchored on GY is promising candidate. The substitution of B can effectively promote the activation of N2 and suppress the hydrogen evolution, while the substitution of N has the minimum ΔG*N-NH of 0.26 eV and ΔGNH3 of 0.08 eV. Compared with two different NRR pathways, the distal mechanism process is more preferential than the alternating pathway. The catalyst of Cr/N-GY has higher stability and can effectively activate N2 to generate *N2H, which can serves as promising catalysts throughout the NRR process.

Activity of CeO2(111) supported Mnx(x = 1–6) for electrochemical N2 reduction reaction: Insights from density functional theory

It is challenging to realize an efficient nitrogen reduction reaction (NRR) under mild conditions, which suffers from low ammonia yield and low Faraday efficiency due to the extremely stable NN triple bond of N2 as well as competitive hydrogen evolution reaction. In this work, the NRR reactivity of Mnx(x= 1–6) clusters supported on CeO2(111) (Mnx(x = 1–6)/CeO2(111)) was systematically investigated using density functional theory. A volcanic relationship between the limiting potential of NRR on Mnx(x = 1–6)/CeO2(111) and the atom number of Mnx was found. Mn3/CeO2(111) shows the highest activity for NRR with a limiting potential of -0.36, -0.55 and -0.53 V along distal, alternating and enzymatic reaction pathway, respectively. Its high activity is attributed to the triangular geometry and optimal average number of electrons every Mn transferred from Mn3 to CeO2(111), which leads to the strong N2 activation and the stabilization of nitrogen-containing intermediates. Also, Mn3/CeO2(111) exhibits a high NRR selectivity by hindering H adsorption and a high thermal stability at both 298 and 773 K, suggesting its promising potential as effective NRR catalyst. This work provides new insights into the rational design of single cluster catalysts.

Effect of sward species diversity combined with a reduction in nitrogen fertilizer on the performances of spring calving grazing dairy cows

The objective of this study was to evaluate the impact of sward diversification combined with a reduction of chemical nitrogen (N) fertilizer on the performance of spring calving grazing dairy cows within a farm systems experiment. Three farmlets were created; a monoculture of perennial ryegrass (Lolium perenne L.; PRG) fertilized with 250 kg N/ha (PRG-250N), a PRG - white clover (Trifolium repens; WC) sward fertilized with 125 kg N/ha (PRGWC-125N) and a multispecies sward (MSS) comprising of grasses, legumes and herbs also fertilized with 125 kg N/ha (MSS-125N). Each farmlet had its own herd of dairy cows on a total area of 18.7 ha divided into 20 paddocks. Each herd was comprised of pure Holstein-Friesian (HF) and HF Jersey crossbred (JFX) animals and randomly assigned through the 3 treatments. For 3 years (2021 to 2023), the performances of both swards (grass yield, botanical composition, nutritive value) and grazing animals (milk production and composition, body weight (BW) and body condition score (BCS)) were recorded. There were no significant differences in pasture production or sward nutritive value between sward systems and grazing season length was also similar (264 d). On average over the 3 years, PRGWC-125N contained 150 g/kg DM of legumes and the MSS-125N contained 160 g/kg DM legumes, 130 g/kg DM plantain and 40 g/kg DM chicory. Both individual cow milk and fat plus protein (Milk solids; MS) yield were lower for PRG-250N (5,018 and 452 kg, respectively), intermediate for PRGWC-125N (5,139 and 463 kg, respectively) and highest for MSS-125N (5,297 and 476 kg, respectively) while milk and MS production per hectare from grazing were similar during the study period (11,523 and 1,016 kg/ha, respectively). Breed also had a significant effect with the JFX having lower milk yield but higher fat and protein concentration compared with HF. This resulted in higher MS production per kg of BW for the JFX compared with HF (0.96 and 0.87 kg MS/kg BW, respectively). The results of this study highlight the possibility for more diverse pastures to reduce chemical N fertilizer input requirements and maintain pasture productivity while increasing animal performance within pasture-based spring calving systems.

Unveiling F-coordination tuning of dense Fe-N4 active sites via nitrogen fixation over advanced electrocatalysts

The manuscript presents a significant advancement in the field of electrocatalytic nitrogen fixation by unveiling the role of fluorine coordination in tuning the activity of atomically dispersed iron-nitrogen (Fe-N4) active sites within porous carbon (PC). The innovative approach employs chemical vapor deposition (CVD) to fabricate F-Fe-NC active sites, which, upon fluorination, modulate the electronic configuration of iron, enhancing nitrogen adsorption and activation. The F-Fe-NC catalyst demonstrated a remarkable enhancement in electrocatalytic nitrogen reduction reaction (NRR) performance, achieving an ammonia yield rate (RNH3) of 125.49 μg h−1 mgcat.−1 and a Faradaic efficiency (FE) of 25.19 %. In-situ electrochemical mass spectrometry and Density Functional Theory (DFT) calculations were utilized to dissect the NRR kinetics and elucidate the underlying reaction mechanism, identifying the potential-determining step. The study introduces a novel, high-performance catalyst for electrocatalytic NRR and provides a practical strategy for optimizing the active-site microenvironment, laying the groundwork for the future commercial application of electrocatalytic NRR processes.

Oxygen vacancies-rich molybdenum tungsten oxide nanowires as a highly active nitrogen fixation electrocatalyst

Herein, vacancy engineering is utilized reasonably to explore molybdenum tungsten oxide nanowires (W4MoO3 NWs) rich in O-vacancies as an advanced electrochemical nitrogen reduction reaction (eNRR) electrocatalyst, realizing further enhancement of NRR performance. In 0.1 mol/L Na2SO4, W4MoO3 NWs rich in O vacancies (CTAB-D-W4MoO3) achieve a large NH3 yield of 60.77 µg h-1 mg-1cat. at -0.70 V vs. RHE and a high faradaic efficiency of 56.42 % at -0.60 V, much superior to the W4MoO3 NWs deficient in oxygen vacancies (20.26 µg h-1 mg-1cat. and 17.1 % at -0.70 V vs. RHE). Meanwhile, W4MoO3 NWs rich in O-vacancies also show high electrochemical stability. Density functional theory (DFT) calculations present that O vacancies in CTAB-D-W4MoO3 reduce the energy barrier formed by the intermediate of *N-NH, facilitate the activation and further hydrogenation of *N-N, promote the NRR process, and improve NRR activity.

Effect of Surface Anions Adsorbed by Rutile TiO2 (001) on Photocatalytic Nitrogen Reduction Reaction: A Density Functional Theory Calculation

The adsorption of common anions found in water can have a considerable impact on the surface state and optical characteristics of titanium dioxide (TiO2), which has an important impact on the photocatalytic nitrogen reduction reaction (NRR). This work utilizes density functional theory (DFT) computations to examine the electronic and optical characteristics of the TiO2 (001) surface under various anion adsorptions in order to clarify their influence on the photocatalytic NRR of TiO2. The modifications in the structure, optical, and electronic properties of TiO2 before and after anion adsorption are investigated. In addition, the routes of Gibbs free energy for the NRR are also evaluated. The results indicate that the adsorption of anions modifies the surface characteristics of TiO2 to a certain degree, hence impacting the separating and recombining charge carriers by affecting the energy gap of TiO2. More importantly, the adsorption of anions can increase the energy barriers for the NRR, thereby exerting a detrimental effect on its photocatalytic activity. These findings provide a valuable theoretical contribution to understanding the photocatalytic reaction process of TiO2 and its potential application of NRR in the actual complex water phase.

Nitrogen reducing mechanism by microporous aeration based on microbial population characteristics: water temperature factor

ABSTRACT The formation of black odour water is primarily attributed to the elevated concentration of organic pollutants, along with an excessive amount of nitrogen and phosphorus, ultimately leading to an anoxic aquatic environment. The water temperature influence mechanism on black-odorous water restoration by microporous aeration is still lacking depth study. This paper selected (15–18) ℃ (spring and autumn), (22–25) ℃ (summer), (8–11) ℃ (winter) as temperature conditions, and investigated temperature influence on nitrogen reduction. Researches showed that: (1) The removal rates of COD, NH4 +-N and TN were significantly positively correlated with temperature (r = 0.99, 0.96, 0.97), the lowest removal rates were 83.16%, 95.68%, 58.7% ((8–11) ℃), the highest values were 92.67%, 98.27%, 70.96% ((22–25) ℃), respectively. (2) At a temperature range of 22–25°C, the microbial community exhibited the highest levels of abundance, diversity, and uniformity. Notably, Proteobacteria dominated this temperature range with a relative abundance of 79.72%. Furthermore, temperature positively correlated with the majority of dominant bacterial species, suggesting that conditions at 22–25°C are highly conducive to the growth of most bacterial communities. Among these, Limnohabitans, Alsobacter, and Candidatus_Aquirestis, which possess key functions in denitrification and nitrogen removal, displayed significantly higher abundances. It explains the positive correlation between temperature and removal rates of COD, TN and NH4 +-N from microbial population’s perspective. Thus, the best temperature for repairing black-smelly water is (22–25) ℃. This study provides technical reference for mechanism research and practical application of microporous aeration.

Transition metal atoms embedded into B/N co-doped graphene as electrocatalysts toward nitrogen reduction reaction: Search for the optimal combination

The catalytic performance of a series of single transition metal (TM = 3d, 4d, and 5d series) atoms anchored on B/N co-doped graphene (BxNy@Gra) toward electrocatalytic nitrogen reduction reaction (eNRR) was systematically investigated by first-principles calculations. Among 180 possible materials, four catalysts (Tc-B1N3@Gra, Os-B2N2α@Gra, Re-B2N2γ@Gra, Nb-B3N1@Gra) feature the highest activity with UL no higher than 0.31 V. Interestingly, a volcano curve between UL and ΔEads(*NNH) can be established, so ΔEads(*NNH) can be applied as a descriptor to unveil the structure-activity relationship and characterize the activity of catalysts. The properties, thermal stability, and selectivity for the four catalysts were analyzed. Os-B2N2α@Gra is identified as a promising catalyst in this work for catalyzing N2 electroreduction to NH3 owing to its potent catalytic activity (UL = −0.28 V), high stability and distinct selectivity. This work can give some meaningful guidance for rapid screening and the rational design of efficient single-atom catalysts for electrocatalytic ammonia synthesis and other related electrochemical reaction. We expect that the present study will inspire and promote the efforts from both experimental and theoretical in this direction.