H2O Reaction Research Articles

Predicting Rate Constants of Hydrogen Abstraction Reactions between OH/HO2 and Alkanes by Machine Learning Models.

The hydrogen abstraction reactions by small radicals from fuel molecules play an important role in the oxidation of fuels. However, experimental measurements and/or theoretical calculations of their rate constants under combustion conditions are very challenging due to their high reactivity. Machine learning offers a promising approach to predicting thermal rate constants. In this work, three machine learning methods, XGB, FNN, and XGB-FNN hybrid algorithms, were employed to train and predict the rate constants of the hydrogen abstraction reactions between alkanes and OH/HO2. Six descriptors were selected according to the Pearson correlation coefficients, the importance of descriptors, and the clustering heat map. It was proven that the XGB-FNN model is the most robust. The constructed XGB-FNN model achieved an average deviation of 89.13% for the alkanes + OH reactions and 190.93% for the alkanes + HO2 reactions on their respective prediction sets. The model was also used to predict the rate constants of the reactions involving larger alkanes, demonstrating its extrapolation capability. Furthermore, the model has the ability to distinguish the reactivity of the reactions with the hydrogen atom abstracted at different sites of alkane.

Tropospheric Fate of Methylhydroxycarbene and the Ability of a Single Water Molecule to Efficiently Promote Its Isomerization into Acetaldehyde.

The ultraviolet (UV) photodissociation of pyruvic acid through the absorption of solar actinic flux generates methylhydroxycarbene (MHC) in the atmosphere. It is recognized that isolated MHC can undergo unimolecular isomerization to form acetaldehyde and vinyl alcohol. However, the rates and mechanism for its possible bimolecular reactions with atmospheric constituents, which can occur in parallel with its unimolecular reaction, is not well understood. Here we investigate the energetics, kinetics, and mechanism of the reaction of MHC with three ubiquitous atmospheric molecules N2, O2, and H2O over the 160 K-380 K temperature range. Our study, at the CCSD(T)/6-311++G(3df,3pd)//M06-2X/6-311++G(3df,3pd) level, reveals that the MHC + N2 encounter is nonreactive, while the MHC + O2 reaction, which leads to CH3CO + HO2 formation, has a rate that is significantly different from previous estimates. For the MHC + H2O reaction, we find that a single H2O molecule is very effective in catalyzing the isomerization of MHC to form predominantly acetaldehyde. An analysis of the computed rate for this reaction indicates that it will be an important source of tropospheric acetaldehyde ̵ a major pollutant and precursor for atmospheric reactive intermediates. Our findings are in sharp contrast to current assessments in the literature that the MHC + H2O reaction is minor. Furthermore, in the MHC + H2O reaction system, we find that due to the presence of the OH group on MHC, the concerted insertion mechanism, which is typically dominant in reactions involving singlet carbenes, is suppressed relative to a hydrogen bond mediated double hydrogen atom transfer mechanism.

Regiospecific Alkene Oxyamination via N‐Alkylation‐ Hydroxylation‐Transesterification Cascades

AbstractAn unprecedented cascade reaction of simple inactive alkenes, azo compounds and H2O to produce valuable poly‐substituted oxazolidinones is reported herein. The transformation possesses exclusive regioselectivity and features mild reaction conditions and a broad substrate scope. Mechanistic studies indicated this transformation underwent a N‐alkylation‐hydroxylation‐transesterification cascade process. This research not only pushes the boundaries of the essential difunctionalization of alkenes but also exploits a new chemistry for azo compounds.

Catalytic pyrolysis mechanism of tetrabromobisphenol A by calcium oxide: A density functional theory study

In this paper, the mechanisms of catalytic pyrolysis of tetrabromobisphenol A (TBBPA) by calcium oxide (CaO) were studied through density functional theory methods. The results indicate that the phenolic hydroxyl group of TBBPA is the preferred site for CaO to extract protons, and the generated anion further transforms into 2,6-dibromophenol via demethylation and hydrogen transfer reactions. The reaction activity of CaO with hydrogen bromide is relatively high, with an energy barrier of 133.2 kJ/mol. CaO produces calcium ions, which combine with bromine ions to form calcium bromide to achieve the purpose of fixing bromine. In addition, the participation of calcium ions results in the OH bond being easier to crack, which further lowers the reaction energy barrier of keto-enol tautomerism reactions H2O produced during catalytic pyrolysis also has an obvious catalytic effect, and the energy barrier of the keto-enol tautomerism reaction decreased from 309.1 kJ/mol to 150.6 kJ/mol with the participation of H2O.

Clarify the process of overshoot voltage generation of proton exchange membrane electrolyzer under intermittent operation

Overshoot voltage phenomenon often occurs when the proton exchange membrane (PEM) electrolyzer is in the intermittent operation, which makes H2 production energy consumption increase significantly and its lifetime reduce rapidly, especially to the high-power electrolyzers in the industrial applications. Up to now, the phenomenon has been rarely understood and its process is elusive. Therefore, in this work, firstly, we find that the polarization curve of PEM electrolyzers happening S distortion synchronize with the appearance of overshoot voltage phenomenon. Secondly, through in-situ Raman characterization, we find that involvement and disappearance of H2O in the hydrogen evolution reaction (HER) is the key factor causing and resolving this phenomenon. Finally, we used EPMA to exclude metal cations affection. Also, by micro-CT, EIS test, visualization PEM electrolyzer inside model and COMSOL electromagnetic simulation, we find that anode catalyst layer porosity reduction directly affects water absorption of membrane as well as current variation leads to eddy currents generation which is deepen unequal current distribution. These are two important reasons for the involvement of H2O in HER. In summary, these findings elucidate the mechanism of overshoot voltage phenomenon for the first time, which contributes to design novel electrical protection schemes and advanced membrane electrodes for PEM electrolyzers, thus they can help to achieve cost reduction and efficiency improvement in the green hydrogen industry.

Highly Selective Synthesis of Acetic Acid from Hydroxyl‐Mediated Oxidation of Methane at Low Temperatures

AbstractDirect methane conversion and, in particular, the aerobic oxidation to acetic acid, remain an eminent challenge. Here, we reported a zeolite‐supported Au−Fe catalyst (Au−Fe/ZSM‐5) that converted methane to acetic acid with molecular oxygen as an oxidant in the presence of CO. Specifically, Au nanoparticles catalyzed the formation of hydroxyl species from the reaction of CO, O2, and H2O, meanwhile ZSM‐5‐supported atomically dispersed Fe species were responsible for the hydroxyl‐mediated coupling of CH4 and CO to generate acetic acid. The reaction over 50 mg of Au−Fe/ZSM‐5 under 62 bar (CH4 : CO : O2=14 : 14 : 3) at 120 °C for 3.0 h yielded 5.7 millimoles of acetic acid per gram of the catalyst (mmol gcat−1) with the selectivity of 92 %, outperformed most of reported catalysts. Significantly, the catalyst remained active even at 60 °C. We anticipate that this hydroxyl‐mediated route may guide the design of optimized catalysts for the direct methane functionalization at low temperatures.

Experimental and modeling studies on char combustion under pressurized O2/H2O conditions

The desorption kinetic parameters for pressurized combustion and gasification reactions were determined based on a C++ program coupled with the Langmuir-Hinshelwood (L-H) kinetic model developed and experimental data from pressurized char combustion, and the established L-H kinetic model for pressurized char-O2/H2O combustion was refined in the current paper. The activation energy for desorption in reactions involving pressurized char-O2 and char-H2O was determined to be 250.8 kJ/mol, accompanied by a pre-exponential factor of 5.42 × 1010 g/(m2 s). Using this foundation, the current research conducted simulations to investigate the impacts of temperature, pressure, and H2O concentration on the oxidation adsorption rate (Rads,oxi), desorption rate (Rdes), gasification adsorption rate (Rads,gas), and the competitive influences of kinetics and diffusion processes within the pressurized char-O2/H2O combustion. The simulation results indicate a gradual increase in Rdes and Rads,gas with char conversion to reach a peak, followed by a gradual decline. Conversely, the Rads,oxi varies smoothly throughout the char conversion process. At 1673 K/1.0 MPa, the char-O2/H2O reaction rate is primarily constrained by Rads,oxi and Rads,gas, with the adsorption reaction serving as the rate-controlling step. Moreover, it was noted that a rise in pressure resulted in a linear increase in Rads,oxi, Rdes, and Rads,gas. At elevated temperatures, the impact of pressure on them becomes more noticeable. However, the introduction of H2O mitigates this effect. Elevated temperature and pressure facilitate the competition on the kinetics of char-O2 combustion for O2 diffusion, resulting in the conversion of char being more susceptible to O2 diffusion rate limitation. With the addition of 20 % H2O, the competition effect was weakened. In the case of pressurized combustion involving char and O2/H2O, the char conversion is primarily constrained by the O2 diffusion rate and is scarcely influenced by the H2O diffusion rate.

Hindrance of complete fusion in $$^{18}$$O + $$^{165}$$Ho reaction at above the barrier energies: Role of angular momentum

Hindrance of complete fusion in $$^{18}$$O + $$^{165}$$Ho reaction at above the barrier energies: Role of angular momentum

In-situ atomic hydrogen generation: A key to elevating membrane cleaning via citric acid-modified Fenton-like system

Oxidation process has been widely used to clean irreversible membrane fouling, and the development of novel oxidative cleaning process has attracted worldwide attention. In this study, a novel cleaning process with the combination of sodium percarbonate (SPC), citric acid (CA), and ferrous ion (Fe(II)) was introduced to remove organic fouling derived from the complexation of humic acid (HA) and calcium ions (Ca2+) for the first time. Remarkably, both flux recovery and resistance removal could reach 99 % within one hour. The efficiency and durability of this novel cleaning system were confirmed through comprehensive characterization and cyclic cleaning test of the ultrafiltration membranes. Furthermore, it effectively removed various natural organic matter-induced fouling and performed well in long-term experiments. This outstanding performance is due to the synergy between oxidative hydroxyl radicals (HO) and reductive atomic hydrogen (H*) in SPC/CA/Fe(II). Analysis of intermediate/final products confirmed that H* is generated through the reaction of CA and HO and absorbed by HA. Confocal laser scanning microscopy (CLSM) revealed that this absorption makes HA more susceptible to HO attack, resulting in enhanced cleaning performance. This mechanism demonstrates the potential of advanced reduction–oxidation systems for membrane cleaning, offering new insights for the development of novel cleaning methods.

Oxygen isotope fractionation during amorphous to crystalline calcium carbonate transformation at varying relative humidity and temperature

Crystalline calcium carbonate isotope compositions have been widely used to reconstruct past environments. However, if their isotopic compositions are modified because of crystallization from an amorphous precursor, their reliability as paleo-geochemical proxies can be compromised. This study explored the changes in the oxygen isotope compositions during the transformation of amorphous calcium carbonate (ACC) into crystalline carbonate under different conditions of relative humidity (RH of 33–95 %), temperature (T of 5 °C and 20 °C) and in the presence/absence of atmospheric CO2. The data showed that at low RH and T (e.g., RH ≤ 45 % and 5 °C) when a complete ACC-crystalline carbonate transformation did not take place then the original ACC δ18O values (δ18OCaCO3 = −15.9 ± 1.0 ‰, VPDB) were preserved throughout the experimental runtime (up to 144 days). In contrast, in fully crystallized CaCO3 (e.g., at RH ≥ 60 %) the δ18OCaCO3 values increased rapidly over the first few days, followed by a slower and gradual increase. By the end of the experiments (i.e., after 103–144 days) the crystalline δ18OCaCO3 values ranged from −10.4 ‰ to −8.1 ‰ in the presence of atmospheric CO2 and from −12.6 ‰ to −9.5 ‰ in the CO2-free experiments. These changes in oxygen isotope compositions of the CaCO3 reaction products (calcite and/or vaterite) were mainly driven by exchange with H2O from the hydrated ACC i.e. the synthesis fluid. In CO2-present experiments, oxygen isotope fractionation factors between the CaCO3 reaction products and the synthesis fluid (18αc–w) approached or exceeded oxygen isotope equilibrium values. This could be explained by a decrease in the initially high pH of the aqueous fluid released from ACC dissolution during CO2 hydration/hydroxylation, which would have increased the oxygen isotope exchange kinetics between H2O and dissolved inorganic carbon (DIC). In some experiments, the hydration/hydroxylation of 18O-enriched CO2, due to isotopic salt-effects, might have also resulted in 18O-enriched calcium carbonates and calculated fractionation factors that exceeded equilibrium values. In the CO2-free experiments, isotopic equilibrium between the crystalline phase and the synthesis fluid was not reached. This oxygen isotope disequilibrium suggests that without the pH lowering effect of the hydroxylation/hydration of CO2, the CO32− released during ACC/calcite dissolution-reprecipitation may have not isotopically equilibrated with the high pH synthesis fluid due to the long equilibration times required to reach isotope equilibrium at high pH values, leading to the self-buffering of δ18OCaCO3 values. The results suggest that the oxygen isotopic compositions of natural carbonates formed from ACC transformation in air and at low water/solid ratio (e.g., biominerals or carbonates formed in caves) are complex and cannot be used as simple proxies if the reaction kinetics (RH/CO2/T) and H2O sources are not known and quantified.

Unclassical Radical Generation Mechanisms in the Troposphere: A Review.

Hydroxyl (OH) and hydroperoxyl (HO2) radicals, collectively known as HOx radicals, are crucial in removing primary pollutants, controlling atmospheric oxidation capacity, and regulating global air quality and climate. An imbalance between radical observations and simulations has been identified based on radical closure experiments, a valuable tool for accessing the state-of-the-art chemical mechanisms, demonstrating a deviation between the existing and actual tropospheric mechanisms. In the past decades, researchers have attempted to explain this deviation and proposed numerous radical generation mechanisms. However, these newly proposed unclassical radical generation mechanisms have not been systematically reviewed, and previous radical-related reviews dominantly focus on radical measurement instruments and radical observations in extensive field campaigns. Herein, we overview the unclassical generation mechanisms of radicals, mainly focusing on outlining the methodology and results of radical closure experiments worldwide and systematically introducing the mainstream mechanisms of unclassical radical generation, involving the bimolecular reaction of HO2 and organic peroxy radicals (RO2), RO2 isomerization, halogen chemistry, the reaction of H2O with O2 over soot, epoxide formation mechanism, mechanism of electronically excited NO2 and water, and prompt HO2 formation in aromatic oxidation. Finally, we highlight the existing gaps in the current studies and suggest possible directions for future research. This review of unclassical radical generation mechanisms will help promote a comprehensive understanding of the latest radical mechanisms and the development of additional new mechanisms to further explain deviations between the existing and actual mechanisms.

H2O-based atomic layer deposition mechanism of aluminum oxide using trimethylaluminum

As a nanofabrication technology, atomic layer deposition (ALD) has been widely used in the fields of displays, microelectronics, nanotechnology, catalysis, energy and coatings. It demonstrates excellent conformality, large-area uniformity and precise control of the sub-monolayer film. Al2O3 ALD using trimethylaluminum (TMA) and water (H2O) as precursors is the most ideal ALD model system. In this work, the reactions of TMA and H2O with the surface have been investigated using density functional theory (DFT) calculations in order to obtain more information on the reaction mechanism of the complicated H2O-based ALD of Al2O3. In the TMA reaction, the methyl ligands can be eliminated and new Al-O bonds can be formed via ligand exchange reactions. In the H2O reaction, the methyl ligand on the surface can be further eliminated and new AlO bonds can be formed. Meanwhile, the coupling reactions between the surface methyl and hydroxyl groups can further form new AlO bonds and release CH4 or H2O to densify the Al2O3 film. These complicated reaction mechanisms of Al2O3 H2O-based ALD can provide theoretical guidance for the precursor design and ALD growth of other oxides and aluminum-based compounds.

Liquid-liquid addition reaction of ethylene oxide with hydrazine hydrate in microreactors: Kinetics and process optimization

The addition reaction of ethylene oxide (EO) and hydrazine hydrate (N2H4·H2O) to β-hydroxyethyl hydrazine (HEH) is an important process for the synthesis of hydrazine-derived monopropellant in the aerospace industry. Due to the complexity of this reaction mechanism, it is difficult to reduce the formation of byproducts and efficiently obtain pure HEH. Hence it is necessary to investigate process behavior and establish kinetic network for further optimization. Here a continuous microflow system was developed to systematically investigate the synthesis of HEH under high pressure in the liquid–liquid form. A simple and effective pre-column derivatization method was applied to characterize and quantify the product. Subsequently, a thorough optimization of parameters, including N2H4·H2O concentration, molar ratio (N2H4·H2O/EO), temperature and reaction time, was conducted. Additionally, response surface methodology was employed to optimize the reaction conditions, illuminating the intricate interactions among the specified variables and achieving a high HEH yield of 96.97 %. Finally, a kinetic model was established, and the activation energies for the main reaction and side reaction were measured to be 38.31 kJ·mol−1 and 44.94 kJ·mol−1, respectively. This kinetic model can enable the accurate determination of kinetic parameters and provide guidance for the process intensification of this EO addition reaction.

Zero-Point-Energy Driven Isotopic Exchange of the [H3O]- anion Probed by Mid-Infrared Action Spectroscopy.

We present the first observation of vibrational transitions in the [H3O]- anion, an intermediate in the anion-molecule reaction of water, H2O, and hydride, H-, using a laser-induced isotopic H/D exchange reaction action spectroscopy scheme applied to anions. The observed bands are assigned as the fundamental and first overtone of the H2O-H- vibrational stretching mode, based on anharmonic calculations within the vibrational perturbation theory and vibrational configuration interaction. Although the D2O·D- species has the lowest energy, our experiments confirm the D2O·H- isotope to be a sink of the H/D exchange reaction. Ab initio calculations corroborate that the formation of D2O·H- is favored, as the zero-point-energy difference is larger between D2 and H2 than between D2O·H- and D2O·D-.

Region-oriented simultaneously joint two-pollutant control strategies are required to substantially reduce deaths attributed to both PM2.5 and ozone pollution in China

China is confronting serious air pollution of fine particulate matter (PM2.5) and ozone, which routinely exceed air quality standards. PM2.5 concentrations decreased by 30–40% while ozone increased by 15–20%, across China during 2015–2019. This could be attributed to targeted clean air policies that have focused more on controlling particulate matter since 2013. The deaths attributable to PM2.5 and ozone exposure over China changed from 1.45 to 0.13 million in 2015 to 1.04 and 0.21 million in 2019, respectively. The changes in mortality, PM2.5 and ozone present spatially heterogeneous patterns across cities and regions. The ozone production regimes (NOx -limited, volatile organic compounds (VOCs)-limited or transition between them), the responses of P(O3) to the change in NOx and VOCs, the reactions of HO2, OH, and RO2, and meteorological conditions, are regionally dependent and spatially heterogeneous. Our results have important implications for developing a smarter, region-oriented, two-pollutant coordinated control policy for VOCs and NOx in China.

Environmental fate of phenobarbital in water: Homogeneous and non-homogeneous environment

In aqueous environments, phenobarbital (PB) undergoes degradation mediated by hydroxyl radicals (HO·) and sulfate radicals (SO4·−). In this study, a theoretical approach was used to investigate the oxidation of phenobarbital triggered by HO·/SO4·− in different dissociated forms of PB at different pH values, as well as the adsorption mechanism of phenobarbital on the silica surface and the non-homogeneous reaction with HO·. Our study confirms three primary reaction models for PB degradation: radical addition, hydrogen abstraction, and single electron transfer reactions. Thermodynamic and kinetic calculations show that the reaction of PB with HO· is the main degradation pathway compared to the reaction of SO4−. At the C5 and C6 positions, HO·-addition and H-abstraction from H6 and H7 are competitive mechanisms. However, in non-homogeneous environments, HO·-addition at C5 becomes the dominant pathway. Our work identifies the primary products of these degradation reactions. At a temperature of 298 K, the total rate constants for the degradation reactions of HO· with PB neutral molecules and anions were determined to be 2.06 M−1 s−1 and 4.11 × 107 M−1 s−1, respectively. In a non-homogeneous reaction with HO·, the total rate constant is 4.47 × 1010 M−1 s−1. Despite degradation, the majority of these products retain their potential to impact aquatic organisms. In particular, compounds such as 5-ethyl-5-hydroxypyrimidine-2,4,6(1H,3H,5H)-trione, 5-(1-hydroxyethyl)-5-phenylpyrimidine-2,4,6(1H,3H,5H)-trione, and 5-acetyl-5-phenylpyrimidine-2,4,6(1H,3H,5H)-trione have a greater toxic effect on green algae. The findings underscore the need for future research to consider the environmental implications and ecotoxicity of PB. Such consideration is crucial for a comprehensive understanding of the long-term environmental impact of pharmaceutical residues in aquatic ecosystems.

Suppressing Competing Solvent Reduction in CO2 Electroreduction with a Magnetic Field.

The presence of an external magnetic field is found to affect the competition between the H2O and CO2 reduction reactions by increasing mass transport via the Lorentz force. Increasing the magnetic field strength at the electrode surface from 0 to 325 mT increases the selectivity of CO over H2 by 3×, while an increase in current density from 0.5 to 5 mA/cm2 increases the selectivity of CO production by 5×. Cyclic voltammetry and finite-element simulations reveal that the origin of the enhanced CO selectivity is attributable to a magnetic field lowering the electrode-electrolyte interfacial pH. A drop in interfacial pH enables increased production of CO from CO2 reduction due to a decrease in the activity of H2O reduction and increase in CO2 solubility near the electrode surface. The insight provided in this study offers new opportunities to control reaction selectivity in electrocatalysis with magnetic field vectors.

Mechanistic and kinetic insights of the formation of allene and propyne from the C3H3 reaction with water.

Allene (H2C = C = CH2) and propyne (CH3-C≡CH) are important compounds in the combustion chemistry. They can be created from the reaction of proparyl radicals with water. In this study, therefore, a computational study into the C3H3 + H2O potential energy landscape has been carefully conducted. The computed results indicate that the reaction paths forming the products (allene: CH2CCH2 + •OH) and (propyne: HCCCH3 + •OH) prevail under the 300-2000K temperature range, where the latter is much more predominant compared to the former. However, these two products are not easily formed under ambient conditions due to the high energy barriers. In the 300 - 2000K temperature range, the branching ratio for the propyne + •OH product declines from 100 to 86%, whereas the allene + •OH product shows an increase, reaching 14% at 2000K. The overall bimolecular rate constant of the title reaction can be presented by the modified Arrhenius expression of ktotal = 1.94 × 10-12 T0.14 exp[(-30.55kcal.mol-1)/RT] cm3 molecule-1s-1. The total rate constant at the ambient conditions in this work, 2.37 × 10-34 cm3 molecule-1s-1, was found to be over five orders of magnitude lower than the total rate constant of the C3H3 + NH3 reaction, 7.98 × 10-29 cm3 molecule-1s-1, calculated by Hue et al. (Int. J. Chem. Kinet. 2020, 4(2), 84-91). The results in this study contribute to elucidating the mechanism of allene and propylene formation from the C3H3 + H2O reaction, and they can be used for modeling C3H3-related systems under atmospheric and combustion conditions. All the geometric structures of the C3H3 + H2O system were optimized by the B3LYP method in conjunction with the 6-311 + + G(3df,2p) basis set. Single-point energies of these species were calculated at the CCSD(T)/6-311 + + G(3df,2p) level of theory. The CCSD(T)/CBS level has also been used to compute single-point energies for the two major reaction channels (C3H3 + H2O → allene + •OH and C3H3 + H2O → propyne + •OH). Rate constants and branching ratios of the key reaction channels were calculated in the 300-2000K temperature interval using the Chemrate software based on the transition state theory (TST) with Eckart tunneling corrections.

Copper hydride species activated hypophosphite hydrolysis towards litre-level and high-purity hydrogen production

Large-scale generation of high-purity hydrogen (H2) from simple hydrolysis strategy is vital, but the traditional technologies remain problems of economy and efficiency. Herein, a new and low-cost technical route is highlighted to realize the litre-level and efficient production of high-purity H2 from sodium hypophosphite (NaH2PO2) hydrolysis at room temperature. The formation and stabilization of CuH species on the designed Cu–Cu2O/CuH catalyst plays a key role in stimulating a continuous reversible NaH2PO2 hydrolysis cycle for H2. Impressively, this new technology achieves the high generated rate of 3.3 L h−1•cm−2 for H2 in alkaline media, which outperforms the other existing hydrolysis technologies. The proposed catalytic mechanism involves renewable CuH active species catalyzing the spontaneous reaction of NaH2PO2 and H2O to form H2 gas and phosphate. From the view of practical application, the developed coupling catalytic system also operates efficiently in deionized water, seawater and tap water solutions, shows unique interference immunity and high stability of convenient H2 generation.

Efficient screening and catalytic mechanism of TM@β-Te for nitrogen reduction reaction

At present, nitrogen reduction reaction (NRR) has become one critical method for NH3 production through the single-atom catalyst (SAC). A variety of TM@β-Te SACs, constructed by 28 transition metal (TM) atoms anchoring on monovacant β-Te substrate, are systematically investigated by using DFT calculations. An efficient “six-step” screening scheme is proposed to screen out potential NRR catalysts, during which the implicit and explicit solvent models are involved to evaluate competitive reactions of H2O and H+. The final selected (Ta, W)@β-Te catalysts have limiting potentials (UL) of −0.32 V and −0.37 V, respectively. Three intrinsic descriptors of φ (the ratio of number of valence electrons and electronegativity of TM atom), ΔG∗N(adsorption energy of a single N atom on the substrate) and ICOHP (Crystal orbital Hamiltonian integrals for TM-N bonds) are proposed and their correlations with UL are investigated to expound the catalytic activity and mechanism. The relationships of dN≡N ∼ φ, ΔG∗N2∼ φ, ΔG∗N∼ φ and ICOHP ∼ φ resemble “volcanoes”, where (Ta, W)@β-Te are located near the vertex as potential catalysts, which can be verified by scaling relationship of ICOHP and ΔG∗N. Moreover, the UL ∼ φ, UL ∼ ΔG∗Nand UL ∼ ICOHP can be used to determine the potential catalysts from rough catalyst screening to accurate determination of potential determining step (PDS) in catalytic reaction. The constant potential model is adopted to investigate the influences of electrode potentials on adsorption strength of NRR intermediates. This work is informative for the research of NRR process and catalyst design of monoalkenes, which offers an efficient and dependable approach for screening excellent NRR catalysts and revealing the origin of catalytic activity.