Haber-Bosch Research Articles

Catalytic Nitrogen Fixation Using Well-Defined Molecular Catalysts under Ambient or Mild Reaction Conditions.

Ammonia (NH3) is industrially produced from dinitrogen (N2) and dihydrogen (H2) by the Haber-Bosch process, although H2 is prepared from fossil fuels, and the reaction requires harsh conditions. On the other hand, microorganisms have fixed nitrogen under ambient reaction conditions. Recently, well-defined molecular transition metal complexes have been found to work as catalyst to convert N2 into NH3 by reactions with chemical reductants and proton sources under ambient reaction conditions. Among them, involvement of both N2-splitting pathway and proton-coupled electron transfer is found to be very effective for high catalytic activity. Furthermore, direct electrocatalytic and photocatalytic conversions of N2 into NH3 have been recently achieved. In addition to catalytic formation of NH3, selective catalytic conversion of N2 into hydrazine (NH2NH2) and catalytic silylation of N2 into silylamines have been reported. Catalytic C-N bond formation has been more recently established to afford cyanate anion (NCO-) under ambient reaction conditions. Further development of direct conversion of N2 into nitrogen-containing compounds as well as green ammonia synthesis leading to the use of ammonia as an energy carrier is expected.

V2O3/VN electrocatalysts with coherent heterogeneous interfaces for selecting low‐energy nitrogen reduction pathways

AbstractElectrochemical nitrogen reduction reaction (NRR) is a sustainable alternative to the Haber‒Bosch process for ammonia (NH3) production. However, the significant uphill energy in the multistep NRR pathway is a bottleneck for favorable serial reactions. To overcome this challenge, we designed a vanadium oxide/nitride (V2O3/VN) hybrid electrocatalyst in which V2O3 and VN coexist coherently at the heterogeneous interface. Since single‐phase V2O3 and VN exhibit different surface catalytic kinetics for NRR, the V2O3/VN hybrid electrocatalyst can provide alternating reaction pathways, selecting a lower energy pathway for each material in the serial NRR pathway. As a result, the ammonia yield of the V2O3/VN hybrid electrocatalyst was 219.6 µg h−1 cm−2, and the Faradaic efficiency was 18.9%, which is much higher than that of single‐phase VN, V2O3, and VNxOy solid solution catalysts without heterointerfaces. Density functional theory calculations confirmed that the composition of these hybrid electrocatalysts allows NRR to proceed from a multistep reduction reaction to a low‐energy reaction pathway through the migration and adsorption of intermediate species. Therefore, the design of metal oxide/nitride hybrids with coherent heterointerfaces provides a novel strategy for synthesizing highly efficient electrochemical catalysts that induce steps favorable for the efficient low‐energy progression of NRR.

Electrocatalytic Coupling of Nitrate and Formaldehyde for Hexamethylenetetramine Synthesis via C-N Bond Construction and Ring Formation.

Hexamethylenetetramine (HMTA) is extensively used in the defense industry, medicines, food, plastics, rubber, and other applications. Traditional organic synthesis of HMTA relies on ammonia derived from the Haber process at high temperatures and pressures. In contrast, electrochemical methods enable a safe and green one-pot synthesis of HMTA from waste NO3-. However, HMTA synthesis through the electrochemical method is challenging owing to the complex reaction pathways involving C-N bond construction and ring formation. In this study, HMTA was efficiently synthesized over electrochemical oxidation-derived copper (e-OD-Cu), with a yield of 76.8% and a Faradaic efficiency of 74.9% at -0.30 VRHE. The catalytic mechanism and reaction pathway of HMTA synthesis on e-OD-Cu were investigated through a series of in situ characterization methods and density-functional theory calculations. The results demonstrated that the electrocatalytic synthesis of HMTA involved a tandem electrochemical-chemical reaction. Additionally, the results indicated that the presence of Cu vacancies enhanced substrate adsorption and inhibited the further hydrogenation of C═N. Overall, this study provides an electrocatalytic method for HMTA synthesis and an electrochemical strategy for constructing multiple C-N bonds.

Green ammonia production via recycle membrane reactor: Experiment and process simulation

With the increasing demand for ammonia (NH3) and the environmental benefits, green and sustainable NH3 production has been urgently developed and is expected to replace the traditional Haber-Bosch (HB) process with high energy consumption and COx emission. In this work, a recycle membrane reactor (RMR) process where a catalytic reactor relates to a membrane separator in series and the retentate stream is recycled to the reactor was designed and executed to produce NH3, in which a Ru (10 wt%)/Cs/MgO catalyst and two membranes with different permeation properties and NH3 selectivity were used. By independently controlling the temperature of the reactor and membrane separator, the synthesized NH3 was selectively extracted from feed side to permeate side by Aquivion/ceramic composite and sulfonated (3-mercaptopropyl)trimethoxysilane membranes. Impressively, NH3 mole fraction was greatly increased from 0.01 of equilibrium state to 0.1–0.45 in permeate stream, which is ascribed to the permeation properties and NH3 selectivity of membrane at different temperatures. Moreover, a one-dimensional, isothermal, and plug-flow model was proposed to simulate RMR, which can be successfully applied to deeply understand the mechanism of RMR. Furthermore, a green NH3 production process based on RMR was simulated to give rationalized suggestions for the NH3 synthesis under mild conditions.

Enhancing Efficiency of Nitrate Reduction to Ammonia by Fe and Co Nanoparticle-Based Bimetallic Electrocatalyst.

The green and sustainable electrocatalytic conversion of nitrogen-containing compounds to ammonia is currently in high demand in order to replace the eco-unfriendly Haber-Bosch process. Model catalysts for the nitrate reduction reaction were obtained by electrodeposition of metal Co, Fe, and bimetallic Fe/Co nanoparticles from aqueous solutions onto a graphite substrate. The samples were characterized by the following methods: SEM, XRD, XPS, UV-vis spectroscopy, cyclic (and linear) voltammetry, chronoamperometry, and electrochemical impedance spectroscopy. In addition, the determination of the electrochemically active surface was also performed for all electrocatalysts. The best electrocatalyst was a sample containing Fe-nanoparticles on the layer of Co-nanoparticles, which showed a Faradaic efficiency of 58.2% (E = -0.785 V vs. RHE) at an ammonia yield rate of 14.6 μmol h-1 cm-2 (at ambient condition). An opinion was expressed to elucidate the mechanism of coordinated electrocatalytic action of a bimetallic electrocatalyst. This work can serve primarily as a starting point for future investigations on electrocatalytic conversion reactions to ammonia using model catalysts of the proposed type.

Highly Efficient Nitrogen Reduction to Ammonia through the Cooperation of Plasma and Porous Metal-Organic Framework Reactors with Confined Water.

While the ambient N2 reduction to ammonia (NH3) using H2O as hydrogen source (2N2+6H2O=4NH3+3O2) is known as a promising alternative to the Haber-Bosch process, the high bond energy of N≡N bond leads to the extremely low NH3 yield. Herein, we report a highly efficient catalytic system for ammonia synthesis using the low-temperature dielectric barrier discharge plasma to activate inert N2 molecules into the excited nitrogen species, which can efficiently react with the confined and concentrated H2O molecules in porous metal-organic framework (MOF) reactors with V3+, Cr3+, Mn3+, Fe3+, Co2+, Ni2+ and Cu2+ ions. Specially, the Fe-based catalyst MIL-100(Fe) causes a superhigh NH3 yield of 22.4 mmol g-1 h-1. The investigation of catalytic performance and systematic characterizations of MIL-100(Fe) during the plasma-driven catalytic reaction unveils that the in situ generated defective Fe-O clusters are the highly active sites and NH3 molecules indeed form inside the MIL-100(Fe) reactor. The theoretical calculation reveals that the porous MOF catalysts have different adsorption capacity for nitrogen species on different catalytic metal sites, where the optimal MIL-100(Fe) has the lowest energy barrier for the rate-limiting *NNH formation step, significantly enhancing efficiency of nitrogen fixation.

High-Entropy Perovskite Oxides as a Family of Electrocatalysts for Efficient and Selective Nitrogen Oxidation.

Electrocatalytic nitrogen oxidation reaction (NOR) can convert nitrogen (N2) into nitrate (NO3-) under ambient conditions, providing an attractive approach for synthesis of NO3-, alternative to the current approach involving the harsh Haber-Bosch and Ostwald oxidation processes that necessitate high temperature, high pressure, and substantial carbon emission. Developing efficient NOR catalysts is a prerequisite, which remains a formidable challenge, owing to the weak activation/dissociation of N2. A variety of NOR electrocatalysts have been developed, but their NOR kinetics are still extremely sluggish, resulting in inferior Faradaic Efficiencies. Here, we report a high-entropy Ru-based perovskite oxide (denoted as Ru-HEP) that can function as a high-performance NOR catalyst and exhibit a high NO3- yield rate of 39.0 μmol mg-1 h-1 with a Faradaic Efficiency of 32.8%. Both our experimental results and theoretical calculations suggest that the high-entropy configuration of Ru-HEP perovskite oxide can markedly enhance the oxygen-vacancy concentration, where the Ru sites and their neighboring oxygen vacancies can serve as unsaturated centers and decrease the overall energy barrier for N2 electrooxidation, thereby leading to promoted NOR kinetics. This work presents an alternative avenue for promoting NOR catalysis on perovskite oxides through the high-entropy engineering strategy.

Design of Major Components of Green Urea Production Plant

Green urea refers to urea produced using renewable energy sources such as municipal solid wastes (MSW) to create a more sustainable and eco-friendly approach to waste management and urea production. As the economy, population, and living standards proliferate swiftly, municipal solid waste has become a significant challenge, particularly in developing countries such as Nepal. This project aims to size the major components of a green urea plant that uses decomposable and combustible waste as feedstock. 15 CSTR digesters with a volume of 53323.2 m3 produced 41473.2 m3 of biogas to convert 740.6 Tons Per Day (TPD) of decomposable waste and 220.06 TPD of combustible waste into 574.4 TPD of green urea. A circulating fluidized bed gasifier, a Proton Exchange Membrane (PEM) electrolyzer, and an air separation unit using the cryogenic process were also selected. The study also involved picking a tubular steam methane reformer as the primary and an auto-thermal steam methane reformer as the secondary steam methane reformer. The shift reaction was carried out using a catalytic water gas shift reactor, and a three-bed type ammonia reactor was chosen for the Haber Bosch process. Finally, the Snamprogetti process was selected for urea synthesis. In addition, the study involves the preparation of a 2D system layout to understand the process flow and a 3D solid works drawing to visualize the plant design. The financial analysis of the green urea plant includes the calculation of CAPEX and OPEX, and it is found that total capital investment is 431.45 M$ and operating expenses are 102.2M$/year. Gasification, steam methane reformer, Air separation unit, ammonia synthesis, urea synthesis, electrolyzer, water gas shift reactor, and anaerobic digestion plant consist 7.15%, 13.55%, 3.32%, 16.13%, 26.12%, 13.37%, 13.43% and 6.93% of total capital investment respectively and 14.62%, 1.61%, 7.78%, 19.73%, 5.71%, 32.6%, 12.9% and 14.62% of total operating costs per year.

Atomic modulation and phase engineering of MoS2 for boosting N2 reduction

Electrochemical nitrogen reduction reaction (ENRR) has emerged as a potential alternative to the conventional Haber-Bosch process for ammonia production. However, ENRR technology is still restricted by the limited Faradaic efficiency due to the hard-to-break N-N triple bond. Herein, inspired by the biomimetic catalyst, we developed a Fe-modulated MoS2 catalyst (named Fe@MoS2) as an efficient ENRR catalyst. Raman spectra, coupled with the X-ray absorption spectroscopy, demonstrate the introduction of Fe into the MoS2 lattice and achieve partial 2H to 1T phase conversion. The presence of S-vacancies on MoS2 substrates was observed on scanning transmission electron microscopy images. Operando infrared absorption spectroscopy confirms that the constructed catalytic site significantly reduces barriers to nitrogen activation. The synthesized Fe@MoS2, with its superior geometric and electronic structures, exhibits a remarkable Faradaic efficiency of 19.7 ± 5.5% at -0.2 V vs. Reversible Hydrogen Electrode and a high yield rate of 20.2 ± 5.3 μg h-1 mg-1 at -0.8 V vs. Reversible Hydrogen Electrode. Therefore, this work provides a fresh direction for designing novel catalysts, eventually boosting the nitrogen reduction reaction kinetics and accelerating the ENRR application.

Catalysts with Trimetallic Sites on Graphene-like C2N for Electrocatalytic Nitrogen Reduction Reaction: A Theoretical Investigation.

Electrocatalytic nitrogen reduction reaction (NRR) is a green and highly efficient way to replace the industrial Haber-Bosch process. Herein, clusters consisting of three transition metal atoms loaded on C2N as NRR electrocatalysts are investigated using density functional theory (DFT). Meanwhile, Ca was introduced as a promoter and the role of Ca in NRR was investigated. It was found that Ca anchored to the catalyst can act as an electron donor and effectively promote the activation of N2 on M3. In both M3@C2N and M3Ca@C2N (M=Fe, Co, Ni), the limiting potential (UL) is less negative than that of the Ru(0001) surface and has the ability to suppress the competitive hydrogen evolution reaction (HER). Among them, Fe3@C2N is suggested to be the most promising candidate for NRR with high thermal stability, strong N2 adsorption ability, low limiting potential, and good NRR selectivity. The concepts of trimetallic sites and alkaline earth metal promoters in this work provide theoretical guidance for the rational design of atomically active sites in electrocatalytic NRR.

Hydroamination of alkenes with dinitrogen and titanium polyhydrides.

An ideal synthesis of alkyl amines would involve the direct use of abundant and easily accessible molecules such as dinitrogen (N2) and feedstock alkenes1-4. However, this ambition remains a great challenge as it is usually difficult to simultaneously activate both N2 and a simple alkene and combine them together through carbon-nitrogen (C-N) bond formation. Currently, the synthesis of alkyl amines relies on the use of ammonia produced through the Haber-Bosch process and prefunctionalized electrophilic carbon sources. Here we report the hydroamination of simple alkenes with N2 in a trititanium hydride framework, which activates both alkenes and N2, leading to selective C-N bond formation and providing the corresponding alkyl amines on further hydrogenation and protonation. Computational studies reveal key mechanistic details of N2 activation and selective C-N bond formation. This work demonstrates a strategy for the transformation of N2 and simple hydrocarbons into nitrogen-containing organic compounds mediated by a multinuclear hydride framework.

The dual-transition-metal dichalcogenide monolayers anchored with Mn dimer: Promising electrocatalysts for efficient nitrogen reduction reaction

Due to its great efficiency, the electrocatalytic nitrogen reduction reaction (NRR) presents itself as a viable and eco-friendly substitute for the traditional Haber-Bosch ammonia production process. However, it is still a formidable task to find electrocatalysts with high activity and selectivity. In this study, a series of transition metals (TM = Ti–Ni, Zr–Mo, Ru–Pd, and Hf–Pt) anchored on 1T′-dual-transition-metal dichalcogenides (1T′-d-TMDs) monolayers (TM2@1T′-CrCoS4) were systematically investigated as electrocatalysts for NRR using first-principles calculations based on density functional theory. Based on a thorough examination of selectivity, high activity, and stability, Mn2@1T′-CrCoS4 and Co2@1T′-CrCoS4 demonstrate exceptional NRR performance. With a limiting potential of −0.11 V, Mn2@1T′-CrCoS4 stood out among them in terms of catalytic activity, favoring the enzymatic pathway. Furthermore, ab initio molecular dynamics (AIMD) simulations were used to assess the dynamic stability of Mn2@1T′-CrCoS4 and Co2@1T′-CrCoS4. To determine the source of increased activities, the density of states (DOS), charge density difference, and crystal orbital Hamilton population analysis were used. According to our research, the 1T′-d-TMDS is a viable substrate for the development of effective NRR catalysts and offers a platform for electrocatalyst experimentation.

Superior electrocatalytic nitrate-to-ammonia conversion activity on CuCo bimetals in neutral media

Electrocatalytic recycling of waste nitrate (NO3-) to valuable ammonia (NH3) has been regarded as a sustainable and promising alternative to the unfriendly Haber-Bosch process. Nevertheless, it is still a challenge to achieve high production rate in a neutral media due to the multi-step electron and proton transfer process. Herein, a nonprecious CuCo tandem catalyst is facilely fabricated and the cooperative active sites enable efficient cascade NO3--to-NH3 conversion with outstanding Faradaic efficiency (FE) and high-rate NH3 generation (95 %, 710 μmol h−1 cm−2 at −0.65 VRHE) in neutral media. In-situ Fourier transform infrared spectroscopy (FTIR) is implemented to identify the reaction intermediates to figure out the tandem pathway. Further combined the density functional theory (DFT) calculations, the structure-activity relationship is unveiled. The introduction of Cu regulates the electronic structure of Co to boost the adsorption capacity of nitrate and shifts the d-band to lower the energy barrier. Moreover, the presence of Cu plays a vital role in inhibiting the binding of H*, which ensures the superior FE. To further maximize the energy utilization efficiency, a two-electrode electrolyzer (Cu45Co55||CuNi) is assembled by replacing the anodic oxygen evolution reaction (OER) with thermodynamically favored 5-hydroxymethylfurfural (HMF) oxidation to produce value-added 2,5-furandicarboxylic (FDCA), an important intermediate in the synthesis of bioplastics. These findings might guide the rational design of efficient and inexpensive electrocatalysts to produce value-added chemicals and hold the promise for contributing to carbon peaking and neutrality goals.

Boosting electroreduction of nitrate to ammonia by modulating the crystalline phase of Fe2O3

Electrocatalytic nitrate reduction reaction (NO3RR) provides an alternative to the conventional Haber-Bosch process for ammonia synthesis and is an effective method for removal of nitrate ions from polluted waters, which is highly significant from both energy and environmental perspectives. However, NO3RR involves the complex eight-electron process alongside various nitrogen-containing intermediates and is also in competition with hydrogen evolution reaction, thus demanding highly active and selective electrocatalysts. In this work we prepare a Ni-doped Fe2O3 electrocatalyst via a solvent-free route. It is found that the addition of Ni induces the crystalline-phase transformation of Fe2O3 from γ-Fe2O3 to α-Fe2O3. The density functional theory (DFT) results reveal that compared to γ-Fe2O3, α-Fe2O3 gives rise to a lower potential-determining step (PDS) energy barrier, leading to the more thermodynamically favourable reaction. By modulating the crystalline phase, the optimal catalyst achieves high ammonia yield rates of > 5000 μg h−1 cm−2 and faradaic efficiencies of > 90 %, showcasing its high electrocatalytic activity and selectivity. From this perspective, this paper provides new insights and strategies for the green nitrate-to-ammonia conversion.

Electrochemical reduction of nitrate to Ammonia: Recent progress and future directions

Ammonia (NH3) is essential for global food production as a key agricultural fertilizer and is increasingly recognized as a renewable energy carrier. The electrochemical nitrate reduction (eNO3RR) method stands out as a promising alternative to the traditional, energy-intensive and CO2-emitting Haber-Bosch process, capable of converting residual NO3– pollutants in water systems into valuable NH3 under ambient conditions. Advancing this process toward commercialization relies on the development of electrocatalysts that are highly active, durable, and cost-effective. This article reviews recent progress in electrocatalyst design aimed at improving the efficiency and selectivity of the NO3– to NH3 conversion. Through an exploration of innovative strategies, including doping, alloying, defect engineering, hybridization and single/dual-atom catalysts, this review details how these methods have markedly enhanced catalyst performance, offering avenues to surmount the challenges posed by traditional pure material-based electrocatalysts. Furthermore, the potential for scaling up these technologies for industrial applications is explored. The objective is to provide a comprehensive overview that not only addresses the scientific and technical challenges but also suggests future directions in the development of sustainable and efficient ammonia synthesis technologies, contributing to global efforts in sustainable energy and agricultural practices.

Innovation Policy Beyond Patents: A Case Study on the Development of Climate-Friendly Fertilizers

Abstract Nitrogen fertilizers have revolutionized agriculture since the early 20th century and made a decisive contribution to combating world hunger. Nevertheless, the technology is controversial today because production is energy-intensive and contributes significantly to climate change. In addition, conventional fertilizers pollute groundwater, rivers and coastal waters. Synthetic nitrogen fertilizer is made from ammonia (NH3) produced by the Haber-Bosch process, for which a patent was filed with the German Imperial Patent Office in 1908 (DE235421). For the urgently needed development of modern climate-friendly fertilizers, patent law seems to have played a minor role so far. The large and patent-active agrochemical corporations in the industrialized countries are focusing on other technologies, leaving fertilizer production to companies with direct access to energy below the global market price. Another reason is the very generous regulation of nitrogen fertilizers. For farmers, the use of less climate-damaging fertilizers is not worthwhile. However, the disruption of supply chains in the wake of Russia’s aggression in Ukraine and the aggravation of climate change could lead to a rethink. In the US, the first support programs for the development of climate-friendly, innovative ‘next-generation’ fertilizers have been launched. This paper examines the interplay of patent law in concert with regulatory law and government funding tools in the area of innovative fertilizers. It starts from the hypothesis that other legal frameworks have a stronger influence on innovation activity than patent law at the moment. But this could change if the regulatory framework were to impose stricter requirements for the use of fertilizers.

Modelling Photocatalytic N2 Reduction to Ammonia: Where We Stand and Where We Are Going.

Artificial ammonia synthesis via the Haber-Bosch process is environmentally problematic due to the high energy consumption and corresponding CO emissions, produced during the reaction and before hand in hydrogen production upon methane steam reforming. Photocatalytic nitrogen fixation as a greener alternative to the conventional Haber-Bosch process enables us to perform nitrogen reduction reaction (NRR) under mild conditions, harnessing light as the energy source. Herein, we systematically review first-principles calculations used to determine the electronic/optical properties of photocatalysts, N2 adsorption and to expound possible NRR mechanisms. The most commonly studied photocatalysts for nitrogen fixation are usually modified with dopants, defects, co-catalysts and Z-scheme heterojunctions to prevent charge carrier recombination, improve charge separation efficiency and adjust a band gap to for utilizing a broader light spectrum. Most studies at the atomistic level of modeling are grounded upon density functional theory (DFT) calculations, wholly foregoing excitation effects paramount in photocatalysis. Hence, there is a dire need to consider methods beyond DFT to study the excited state properties more accurately. Furthermore, a few studies have been examined, which include higher level kinetics and macroscale simulations. Ultimately, we show there is still ample room for improvement with regard to first principles calculations and their integration in multiscale models.

Efficient electrocatalytic reduction of nitrate to ammonia using Cu–CeO2 solid solution

Electrocatalytic nitrate reduction reaction (EC-NITRR) is expected to replace Haber-Bosch process for green ammonia (NH3) production. Currently, many catalysts often result in low NH3 yields and low faraday efficiencies due to the lack of active sites. In this study, Cu-doped CeO2 solid solution catalyst was prepared for EC-NITRR using transition metal ions doping. The addition of Cu significantly improved the oxygen vacancy (Ov) concentration of CeO2 and provided more active sites for NO3− catalysis. Meanwhile, the internal charge transfer capability and surface catalytic kinetics of the catalyst are enhanced by the excellent redox capability of Ce3+ and Cu+. Compared with bare CeO2, the NH3 yield of 7% Cu–CeO2 increased by 1.88 times. This work provides new ideas for the design of green and efficient catalysts for EC-NITRR by identifying the role of Cu in the mechanism of doping regulation of CeO2.

Microwave-Mediated ammonia synthesis over Co2Mo3N catalysts at low pressures

The Haber-Bosch process for ammonia (NH3) synthesis is a major contributor to greenhouse gas emissions and is responsible for > 2 % of the world’s energy consumption each year encouraging the need for alternative renewable-based options. This study investigates an earth-abundant ternary metal nitride (i.e., Co2Mo3N) catalyst to develop a renewable-based NH3 synthesis approach, utilizing an energy-efficient microwave-assisted route. Using a combination of spectroscopic and catalytic measurements coupled with surface analysis techniques, Co2Mo3N was evaluated as a stable and efficient NH3 synthesis catalyst. Results presented here demonstrate NH3 synthesis on Co2Mo3N at ∼420 ℃ and ambient pressure yield ∼0.7 mmolNH3.gcat-1.h−1 and up to ∼12 mmolNH3.gcat-1.h−1 at 28 bar under microwave irradiation. Co2Mo3N displayed an activation energy of ∼72 kJ.mol−1 and yielded NH3 following first-order kinetics with respect to both H2 and N2. These studies illustrate the potential of using this catalyst for a sustainable, cost-effective, and environmentally friendly approach to producing NH3.

Emerging MXene-based electrocatalysts for efficient nitrate reduction to ammonia: recent advance, challenges, and prospects

Ammonia (NH3) plays an irreplaceable role in traditional agriculture and emerging renewable energy. Its preparation in industry mainly relies on the energy-intensive Haber-Bosch process, which is associated with high energy consumption and large CO2 emissions. Recently, the nitrate reduction reaction (NO3-RR) driven by renewable energy has received extensive attention. This reaction can efficiently synthesize NH3 with water as a hydrogen source and NO3- as a nitrogen source under mild conditions, which is conducive to reducing energy consumption and promoting the carbon cycle. It is well known that the properties of electrocatalysts determine the performance of NO3-RR. As an emerging two-dimensional material, MXenes (transition metal carbides/nitrides/carbon nitrides) possess excellent electrical conductivity, large specific surface area and controllable surface functional groups, which shows great application potential in the field of NO3-RR. Herein, this review summarized the structure, properties and synthesis strategies of MXenes to elucidate the possibilities from foundation to application. Then, the latest research progress in applying MXene-based electrocatalysts to NO3-RR was summarized and the applicability of different NH3 detection methods was analyzed. Finally, the present challenges and future prospects of NO3-RR were presented. This review aimed to provide thoughtful insights into the rational design of MXene-based electrocatalysts for sustainable NH3 synthesis.