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Ammonia production has traditionally been done by using the Haber-Bosch process, that operates at extremely high pressure (200–300 bar), has a large carbon footprint, and requires significant energy. For ammonia to be used as a hydrogen carrier, it is desired that it is produced by using modular technologies under benign conditions, yet the economics remain commercially viable. This paper investigates a novel technology for ammonia synthesis by using a microwave-assisted low-pressure reactor. Microwave reactors are compact and can be readily modularized and started/shutdown thus making them ideal to be integrated with the electric grid or with regional/local renewable-based electric generation facilities. For separation of unreacted reactants from the product ammonia, if the traditional condensation separation technology used in the high-pressure Haber-Bosch process is used, then the separation process needs to be operated under cryogenic condition thus adversely affecting the economics. A solid sorbent based separation technology is investigated in this paper. A kinetic model for the microwave-catalytic synthesis process is used. An isotherm model is developed for MgCl 2 –Si adsorbent and used for modeling the dynamic adsorption-desorption cycle. A plant-wide model with heat and mass integration is developed. An economic model is developed and used for economic optimization by using an equation-oriented approach. Since the adsorption-desorption process is dynamic, for techno-economic optimization, a reduced order model for the key performance measures of the adsorption-desorption process as a function of its input and decision variable is developed under cyclic steady-state conditions. For the optimized MW-assisted process, the levelized cost of ammonia is $772/mt as opposed to $808/mt for the conventional Haber-Bosch process for a hydrogen price of $2.07/kg. The MW-assisted process is found to be economically viable in the US market if the hydrogen price is below $4/kg. • Plant-wide model of a novel MW-assisted ammonia synthesis process is developed. • A solid-sorbent based separation technology is investigated for separation. • A reduced model based approach is developed for optimizing the adsorption process. • For the optimized process, the levelized cost of ammonia is found to be $772/mt. • The technology is found to be economically viable for H 2 price below $4/kg. [ABSTRACT FROM AUTHOR]

Industrially, ammonia is generated mainly using the energy-intensive and CO 2 -emitting Haber-Bosch process, which is not conducive to sustainable economic and social development. The chemical looping ammonia synthesis (CLAS) is capable of coupling green energy, which is one of the available alternatives to the Haber-Bosch process, but the ammonia production rate of most of its nitrogen carriers is unsatisfactory. In this work, we designed a self-assembled nitrogen carrier using ZSM-5 molecular sieve (ZSM-5) and nickel (Ni) to modify chromium nitride (CrN). ZSM-5 molecular sieves have a rich pore structure, which enables the gas-phase reactants to react with the lattice nitrogen in the subsurface layer of the nitrogen carrier. Nickel can facilitate the dissociation of hydrogen during hydrogenation due to its higher hydrogen affinity. The ammonia production rate of the nitrogen carrier can reach 451.2 μmol g−1 h−1 at 700 °C and atmospheric pressure, and be able to remain 358 μmol g−1 h−1 after eight cycles. Furthermore, we also propose a full-coverage design strategy for nitrogen carriers: simultaneous optimization of the chemical and mass transfer processes in the nitrogen carrier. This work advances the design of high-performance nitrogen carrier, thus facilitating the applications of CLAS for the distributed ammonia synthesis. [Display omitted] • ZSM-5 molecular sieve was used to construct an efficient mass transfer interface. • Full-coverage optimization: chemical and mass transfer process. • The self-assembled chromium-based nitrogen carrier had a dual active site. • The microscopic mechanism was revealed by DFT calculations. • The ammonia synthesis rate reached 451.2 μmol g−1 h−1. [ABSTRACT FROM AUTHOR]

Ammonia (NH3) is a crucial industrial raw material, but the traditional Haber-Bosch process is energy-intensive and highly polluting. Electrochemical methods for synthesizing ammonia using nitric oxide (NO) as a precursor offer the advantages of operating under ambient conditions and achieving both NO reduction and resource utilization. Defect engineering enhances electrocatalytic performance by modulating electronic structures and coordination environments. In this brief review, the catalytic reaction mechanism of electrocatalytic NO reduction to NH3 is elucidated, with a focus on synthesis strategies involving vacancy defects and doping defects. From this perspective, the latest advances in various catalytic reduction systems for nitric oxide reduction reaction (NORR) are summarized and synthesized. Finally, the research prospects for NO reduction to NH3 are discussed. [ABSTRACT FROM AUTHOR]

Ammonia (NH3) is a crucial industrial raw material, but the traditional Haber-Bosch process is energy-intensive and highly polluting. Electrochemical methods for synthesizing ammonia using nitric oxide (NO) as a precursor offer the advantages of operating under ambient conditions and achieving both NO reduction and resource utilization. Defect engineering enhances electrocatalytic performance by modulating electronic structures and coordination environments. In this brief review, the catalytic reaction mechanism of electrocatalytic NO reduction to NH3 is elucidated, with a focus on synthesis strategies involving vacancy defects and doping defects. From this perspective, the latest advances in various catalytic reduction systems for nitric oxide reduction reaction (NORR) are summarized and synthesized. Finally, the research prospects for NO reduction to NH3 are discussed. [ABSTRACT FROM AUTHOR]

Ammonia (NH3) is a crucial industrial raw material, but the traditional Haber-Bosch process is energy-intensive and highly polluting. Electrochemical methods for synthesizing ammonia using nitric oxide (NO) as a precursor offer the advantages of operating under ambient conditions and achieving both NO reduction and resource utilization. Defect engineering enhances electrocatalytic performance by modulating electronic structures and coordination environments. In this brief review, the catalytic reaction mechanism of electrocatalytic NO reduction to NH3 is elucidated, with a focus on synthesis strategies involving vacancy defects and doping defects. From this perspective, the latest advances in various catalytic reduction systems for nitric oxide reduction reaction (NORR) are summarized and synthesized. Finally, the research prospects for NO reduction to NH3 are discussed. [ABSTRACT FROM AUTHOR]

Ammonia (NH3) is a crucial industrial raw material, but the traditional Haber-Bosch process is energy-intensive and highly polluting. Electrochemical methods for synthesizing ammonia using nitric oxide (NO) as a precursor offer the advantages of operating under ambient conditions and achieving both NO reduction and resource utilization. Defect engineering enhances electrocatalytic performance by modulating electronic structures and coordination environments. In this brief review, the catalytic reaction mechanism of electrocatalytic NO reduction to NH3 is elucidated, with a focus on synthesis strategies involving vacancy defects and doping defects. From this perspective, the latest advances in various catalytic reduction systems for nitric oxide reduction reaction (NORR) are summarized and synthesized. Finally, the research prospects for NO reduction to NH3 are discussed. [ABSTRACT FROM AUTHOR]

Synthetic nitrogen fertilizer is the backbone of modern agriculture, helping to feed ~50% of the world's population. However, the current industrial production, distribution, and use of nitrogen fertilizers are built on an unsustainable foundation of fossil resources, and are energy-intensive, environmentally polluting, and inefficient in their usage. With the rapidly declining cost of renewable electricity, such as solar and wind, it is time to develop and implement the decentralized production and application of nitrogen fertilizer with nonthermal plasma technologies. Such locally sourced production at the farm site, using only air and water as feedstock, circumvents the need for the extensive capital investment and infrastructure required for synthetic nitrogen fertilizer production and storage, as well as the complex and costly distribution networks. It will be adaptive to the intermittency of the solar/wind electricity supply, leave no carbon footprint, and also have the advantage of being easily switched on/off, immediately responding to weather changes and local conditions, such as soil, climate, crops, and farming business models, for precision agriculture. [ABSTRACT FROM AUTHOR]

The development of decarbonized synthesis approaches is a critical step in the fabrication of ammonia, an indispensable chemical and a potential carbon–neutral energy carrier. In this regard, the photocatalytic production technology has gained ample attention as a sustainable alternative to energy-intensive and environmentally detrimental Haber–Bosch process. Here, we present cobalt ferrite nanoparticles supported on microporous ZSM-5 type ferrisilicate zeolite as a desirable novel photocatalyst for the ammonia generation. The zeolite introduced as a microporous support increasing the catalytically active sites. A straightforward one-pot sol–gel method was used to synthesize cobalt ferrite (CoFe2O4) and CoFe2O4/ferrisilicate (CF/FS) nanocomposites with various weight percentages (10, 25 and 50%) of CoFe2O4. The photocatalytic performances of the samples in the production of ammonia were investigated under visible light irradiation. The highest rate of NH4+ production (484.74 µmol L−1 h−1) was achieved using the CF50%/FS photocatalyst. The distribution of < 50 nm-sized CoFe2O4 nanoparticles on the surface of the zeolite, as demonstrated by TEM images, and extensive BET surface areas are presented as convincing evidences for the improved photocatalytic activity paticularly in CF50%/FS photocatalyst. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ultrathin Fe-Ta 2 O 5-x nanobelts were fabricated. • Fe-Ta 2 O 5-x nanobelts showed highly improved surface areas and solar-light harvesting. • Fe doping induced the decreased working function and formation of more oxygen vacancies. • Fe-Ta 2 O 5-x nanobelts exhibited highly enhanced photocatalytic performance. Solar-light photosynthesis of ammonia form N 2 reduction in ultrapure water over the artificial photocatalysts is attractive but still challenging compared with Haber–Bosch process. In this work, ultrathin Fe-Ta 2 O 5-x nanobelts were fabricated via the controllable solvothermal process for ammonia photosynthesis. The formed oxygen vacancies and Fe doping narrowed their bandgap energies and promoted the carriers' separation and transfer for Fe-Ta 2 O 5-x nanobelts. In addition, Fe doping also resulted in the reduced working functions of the samples, indicating a weaker electron binding restriction and stronger separation and transfer of photo-induced carriers. The experimental results showed that Fe-Ta 2 O 5-x nanobelts showed remarkably enhanced photocatalytic ammonia production performance under simulated sunlight irradiation, and the relevant ammonia production rate reached approximately 3030.86 μM g−1 h−1, which was 9.63 times of pristine Ta 2 O 5-x and 491.0 times of commercial Ta 2 O 5 , and a relatively stable photocatalytic ammonia production performance under simulated sunlight irradiation for Fe-Ta 2 O 5-x nanobelts. Meanwhile, it was also found that Fe doping has great influences on the photocatalytic performance under visible light and simulated sunlight irradiation, mainly because of their suitable bandgap energies and enhanced solar-light harvesting capacity. Current work indicates the great potentials of ultrathin tantalum-based functional materials for high-efficiency ammonia photosynthesis. [ABSTRACT FROM AUTHOR]

The Haber–Bosch process is a cornerstone in the field of ammonia production and represents a decisive advance in industrial chemistry. This method, developed in the early 20th century, revolutionizes agriculture and enables the mass production of fertilizers. As the world strives for sustainable energy and environmental protection, alternative methods such as the photo/photoelectrocatalytic nitrogen reduction reaction (NRR) are gaining momentum. By using sunlight, electricity, or a combination of both, these approaches promise sustainable ammonia production with renewable energy sources and innovative materials. Researchers are trying to understand the underlying principles, mechanisms, and advances of these methods to overcome the challenges and optimize their effectiveness. This research is a step toward sustainable energy and agriculture, and offers a greener and more efficient way forward. This review looks at advances in sustainable ammonia production, particularly through photo‐ and photoelectrocatalytic NRRs. It examines the hurdles in implementing these methods and provides an overview of the fundamentals of nitrogen fixation and a comparison of current mechanisms. In addition, thermodynamic, theoretical, and computational studies of these processes are summarized. Various photocatalysts and photoelectrocatalysts used for ammonia production are also presented. [ABSTRACT FROM AUTHOR]

Synthetic nitrogen fertilizer is the backbone of modern agriculture, helping to feed ~50% of the world’s population. However, the current industrial production, distribution, and use of nitrogen fertilizers are built on an unsustainable foundation of fossil resources, and are energy-intensive, environmentally polluting, and inefficient in their usage. With the rapidly declining cost of renewable electricity, such as solar and wind, it is time to develop and implement the decentralized production and application of nitrogen fertilizer with nonthermal plasma technologies. Such locally sourced production at the farm site, using only air and water as feedstock, circumvents the need for the extensive capital investment and infrastructure required for synthetic nitrogen fertilizer production and storage, as well as the complex and costly distribution networks. It will be adaptive to the intermittency of the solar/wind electricity supply, leave no carbon footprint, and also have the advantage of being easily switched on/off, immediately responding to weather changes and local conditions, such as soil, climate, crops, and farming business models, for precision agriculture.

With the increasing demand for flexible operation of ammonia production, the feasibility of using reaction kinetic models to predict the performance of a Haber Bosch reactor in a wide operating range must be evaluated. This study compares the feasibility of a lumped Temkin rate expression with a more complex lumped microkinetic model in predicting turnover rates across diverse temperatures and feed compositions. Evaluation and validation were carried out through ammonia synthesis experiments on a magnetite‐based industrial catalyst at temperatures ranging from 548 K to 773 K and H2 : N2 ratios between 4 : 1 to 1 : 1 at 90 bar. While excellent agreement between model predictions and experiments was observed at 648 K, significant discrepancies emerged at 548 K. These findings are valuable for both state‐of‐the‐art ammonia synthesis reactors and green ammonia plants utilizing electrolysis‐derived hydrogen, where flexible operating conditions are paramount. Moreover, integrating site density as a function of temperature and the partial pressure of H2 into the lumped microkinetic model marks a notable advancement, promising enhanced precision in addressing varied operating conditions. [ABSTRACT FROM AUTHOR]

Ammonia is one of the most important industrial chemicals which is commonly used for producing fertilizers and cleaning solutions, as the refrigerant gas, and as the precursors for making various chemicals. With the goal of sustainable development, ammonia is also proposed as the clean fuel for decarbonized transportation. The current the Haber–Bosch process for ammonia synthesis has large footprint and operates under harsh conditions using fossil fuels as the feedstock, being recognized as the major carbon emission source. Accordingly, call for sustainable production of green ammonia using renewable energies is proposed. Ammonia synthesis assisted by nonthermal plasmas has emerged in recent years as a novel and mild electrified technology, which can potentially be coupled with intermittent renewable energies and green hydrogen. Although being promising, significant development is still needed to advance the technology towards practical applications at scales. Hence, this review comments the progression of key aspects of the plasma-assisted ammonia synthesis such as catalyst and reactor design, mechanistic understanding, and process parameters. The snapshot of the current developments and proposed perspectives hope to provide guidance for the future research efforts to drive the technology towards higher technology readiness levels. [ABSTRACT FROM AUTHOR]

Ammonia, a pivotal chemical feedstock and a potential hydrogen energy carrier, demands efficient synthesis as a key step in its utilization. The traditional Haber‐Bosch process, known for its high energy consumption, has spurred researchers to seek ammonia synthesis under milder conditions. Advances in surface science and characterization technologies have deepened our understanding of the microscopic reaction mechanisms of ammonia synthesis. This article concentrates on gas‐solid phase ammonia synthesis, initially exploring the latest breakthroughs and improvements in thermal catalytic synthesis. Building on this, it especially focuses on emerging external field‐driven alternatives, such as photocatalysis, photothermal catalysis, and low‐temperature plasma catalysis strategies. The paper concludes by discussing the future prospects and objectives of nitrogen fixation technologies. This comprehensive review is intended to provide profound insights for overcoming the inherent thermodynamic and kinetic constraints in traditional ammonia synthesis, thereby fostering a shift towards "green ammonia" production and significantly reducing the energy footprint. [ABSTRACT FROM AUTHOR]

Electrochemical 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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The conversion of atmospheric nitrogen (N2) into ammonia (NH3), known as nitrogen fixation, plays a crucial role in sustaining life on Earth, facing innovation with electrocatalytic and photocatalytic methods. These approaches promise gentler conversions from atmospheric nitrogen to ammonia, diverging from the energy‐intensive Haber‐Bosch process, which requires complex plant infrastructure. Vitality lies in eco‐friendly, cost‐effective, and energy‐efficient pathways. The challenge is that electrocatalysts and photocatalysts for nitrogen reduction have shown low Faraday efficiency, hampered by hydrogen evolution. This work delves into recent strides in electro/photo‐catalytic nitrogen fixation/reduction, deciphering mechanisms, catalysts, and prospects. By unveiling the core principles steering these processes, it dissects efficiency drivers. Experimental and theoretical studies, ranging from density functional calculations/simulations to machine learning‐based catalyst screening, mark the path toward highly efficient catalysts, including single/multi‐atom catalysts embedded in 2D materials. The journey explores diverse catalysts, assessing their performance, spotlighting emerging nanomaterials, heterostructures, and co‐catalyst techniques. Perspectives on future directions and potential applications of electro/photo‐catalytic nitrogen fixation/reduction are offered, by emphasizing their role in sustainable nitrogen management and their implications for global agriculture and environmental sustainability. [ABSTRACT FROM AUTHOR]

Ammonia, poised as a carbon‐neutral energy carrier, holds immense promise in reshaping the future energy landscape. Despite the enduring importance of the Haber–Bosch process in ammonia production, its substantial carbon emissions and energy demands necessitate more sustainable pathways. Here, an advanced ammonia synthesis route, enhanced by photoexcitation is demonstrated, which fundamentally modifies the activation pathways of N2 molecules. This alteration significantly lowers the reaction activation energy, resulting in remarkably improved reaction efficiency. The impact of light excitation culminates in an unprecedented ammonia synthesis rate of 18 mmol g−1 h−1, surpassing the traditional thermal catalytic process by 2.57‐fold. More importantly, light assistance reduces the thermal energy input by ≈16%, making it comparable to thermal catalysis while substantially improving energy utilization. This work introduces a greener strategy for ammonia synthesis, pushing the century‐old fossil‐fueled Haber–Bosch process to a new frontier. [ABSTRACT FROM AUTHOR]

Ammonia (NH3) is a pivotal component for the majority of fertilizers, chemicals, and pharmaceuticals. Its conventional production through the Haber–Bosch process is highly energy-intensive and significantly contributes to CO2 emissions, thereby exacerbating global warming. In parallel, the overuse of agricultural fertilizers and the inadequate industrial wastewater management cause the heavy nitrate (NO3−) pollution which poses huge environmental and health hazards to human beings. In an effort to address these challenges, scientists have been exploring more sustainable methods of ammonia synthesis and strategies to mitigate nitrate pollution. Among these, the electrocatalytic reduction of nitrates to ammonia/ammonium (NO3RR) presents a promising solution. This innovative approach not only reduces the environmental footprint of ammonia production by operating under ambient conditions but also contributes to the purification of water bodies by lowering nitrate levels. This review intricately explores the complexities involved in the electrocatalytic reduction of nitrates to ammonia, shedding light on the nuanced mechanisms underlying the process and elucidating the importance of symmetry-breaking structures. It particularly underscores the pivotal role played by various symmetry-breaking structures in catalysts, which serve to disrupt and invigorate the reaction environment, thus enhancing the efficiency of the electrocatalytic process. In culmination, we offer a comprehensive summary of the advancements in the development of catalysts featuring symmetry-breaking structures, providing insights and forward-looking recommendations for the future engineering of broadly applicable symmetry-breaking structure catalysts. [ABSTRACT FROM AUTHOR]

Ammonia is one of the most important chemicals in the world because it is a feedstock for fertilizer production and, moreover, it has been proposed as a convenient storage media for renewable H2. Currently, it is produced by Haber‐Bosch process, which entails harsh operation conditions and a high carbon footprint, rendering the process difficult to be run by renewable energy. Therefore, substituting the conventional Haber‐Bosch process by other approach less energy‐intensive and carbon‐free is an urgent need. A milder process for ammonia synthesis will enable the implementation of smaller distributed plants more aligned with renewable energies. For this reason, there is a plethora of current research focusing on the development of suitable catalysts with higher activity and selectivity for nitrogen reduction and processes that will work under less severe operating conditions or even at ambient conditions. Some of the most relevant research approaches are here revised and compared. [ABSTRACT FROM AUTHOR]

Artificial ammonia synthesis via the Haber‐Bosch process is environmentally problematic due to the high energy consumption and corresponding CO2 ${_2 }$ 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. [ABSTRACT FROM AUTHOR]

Electrocatalytic nitrate reduction reaction (EC-NITRR) is expected to replace Haber-Bosch process for green ammonia (NH 3) production. Currently, many catalysts often result in low NH 3 yields and low faraday efficiencies due to the lack of active sites. In this study, Cu-doped CeO 2 solid solution catalyst was prepared for EC-NITRR using transition metal ions doping. The addition of Cu significantly improved the oxygen vacancy (O v) concentration of CeO 2 and provided more active sites for NO 3 − 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 CeO 2 , the NH 3 yield of 7% Cu–CeO 2 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 CeO 2. The incorporation of Cu into CeO 2 lattice realizes the synergistic regulation of oxygen vacancy and active sites, which contributes to the desirable Faraday efficiency of 88.15% for electrochemical nitrate reduction. [Display omitted] • 7% Cu–CeO 2 solid solution was fabricated via electrodeposition. • Cu incorporation significantly increased the O v concentration in CeO 2. • The interaction between Cu+ and Ce3+ enhanced the internal charge transfer capability of the catalyst. • 170.56 μg h−1 cm−2 NH 3 yield and 88.15% Faraday efficiency were achieved. [ABSTRACT FROM AUTHOR]

The Haber-Bosch process, commonly used for ammonia synthesis, can be replaced by the electrochemical nitrogen reduction reaction (NRR), which offers a more environmentally conscious and sustainable approach. However, developing electrocatalysts with low potential, high selectivity, and fast reaction kinetics remains challenging. In the current work, we have theoretically calculated the potential of V@B5N3 and V@B7N5 (V = Vanadium) material which serves as an electrocatalyst for NRR using density functional theory (DFT) simulations. Our results reveal that the monolayer of V@B7N5 exhibits remarkable catalytic activity and effectively suppresses the hydrogen evolution reaction at an overpotential of 0.13 V. Furthermore, the potential-determining step involving the conversion of *N2-*N2H demonstrates a favourable energy barrier, indicating facile kinetics. The V@B7N5 monolayer shows promising selectivity, with an anticipated ammonia production efficiency of 99%. These findings open avenues for employing single-atom catalysts under ambient conditions to synthesise ammonia, offering a potential solution for sustainable ammonia production. [ABSTRACT FROM AUTHOR]

[Display omitted] Electrochemical nitrate reduction reaction (NO 3 RR) has been regarded as a promising alternative to the Haber-Bosch process for sustainable and clean NH 3 production. To develop highly active and stable electrocatalysts for NO 3 – to NH 3 production, Cu-based materials have been considered as potential candidates owing to the excellent NO 3 – adsorption to easily overcome the rate determining step of nitrate to nitrite conversion in NO 3 RR, although the poor NH 3 yield rate is still challenging. In this study, we report a hybrid electrocatalyst with Bi dopant substitutionally incorporated on cuboctahedra Cu 2 O platform (Bi/Cu 2 O) via in-situ hydrothermal method. The Bi/Cu 2 O shows the NH 3 yield rate of 2562.56 μg h−1 mg cat -1 and Faradaic efficiency of 99.2 % at −0.8 V versus reversible hydrogen electrode in a neutral electrolyte, which is the highest performance among previously reported Cu-based electrocatalyst for NO 3 RR to NH 3. The interfacial synergetic effect of sufficient protonation from Bi-doped overlayer and efficient NO 3 – adsorption from the Cu 2 O platform results in excellent NO 3 RR performance. The experimental variable investigations with in-situ attenuated total reflectance-Fourier transform infrared measurement elucidate that not only nitrate to nitrite conversion but also the protonation of *NO 2 is the rate limiting step for NH 3 production. [ABSTRACT FROM AUTHOR]

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Ammonia production seeks alternatives to the conventional Haber-Bosch process, with nitrogen reduction reaction (NRR) emerging promising. Addressing the challenge of efficient catalysts, the functionalized graphene-based single atom catalysts (SACs) stand out. While prior studies have favored heteroatom-doped catalysts, the coordination of metal centers with nitrogen atoms remains underexplored. This work investigates transition metal (TM) SACs on nitrogen-doped graphene (N 3 G) using density functional theory (DFT) for electro-catalytic NRR. Results highlight the stability of V@N 3 G, Mo@N 3 G, W@N 3 G, with binding energies of −7.77, −5.43, and −3.89 eV, respectively. Insights into work function, d-band center, N–N bond, and IR stretching's role in N 2 activation are gained through this study. Bader charge analysis reveals electron redistribution between the support and adsorbed N 2. Employing Computational Hydrogen Electrode (CHE) method, comparative free energy diagrams for TM@N 3 G (V, Mo, W) via., enzymatic, consecutive, alternating, and distal pathways outline potential rate determining step (PDS) with and without the Implicit solvation method. Remarkably, W@N 3 G catalyst exhibits the lowest PDS in the presence of solvation energy, surpassing other catalysts. The multi-adsorption of N 2 on W@N 3 G enhances NRR process, stabilizing intermediates for efficient ammonia production. This computational study sheds light on metal center SACs on functionalized graphene support as a potential electro-catalyst for efficient and stable NRR. [Display omitted] • V, Mo, W@N 3 G show excellent stability on N-doped graphene. • Roles of work function, d-band, N–N bond, and IR in NRR elucidated. • Bader charge analysis reveals the dynamics of electron redistribution in N 2 adsorption. • Comparative free energy diagrams for TM@N 3 G highlight PDS via CHE method. • W@N 3 G exhibits lowest energy barrier with solvation, excelling among catalysts. [ABSTRACT FROM AUTHOR]

[Display omitted] • The surface modification can significantly raise the limiting potential with −1.24 V (Ti 2 NF 2) to −0.21 V (Ti 2 BSe 2). • hybridization of the σ 2 p and π* 2 p with Ti 3 d orbitals leads to the evident splitting and downshifting of the σ and π* orbitals. • The work function plays a crucial role to predict the NRR performance by the Gibbs free energy change of the rate-determining step, which can be regulated through the surface termination of MXenes. The electrochemical conversion of nitrogen to ammonia provides an encouraging method to substitute the traditional Haber-Bosch process, owing to its high efficiency and mild reaction conditions. The search for high-performance catalysts and comprehension of catalytic mechanisms remains significant challenges. Herein, we conduct a systematic theoretical calculation of the NRR performance and mechanism of 24 Ti 2 XT 2 (X = B, C, N; T = F, Cl, Br, I, O, S, Se, Te) MXenes with a T -vacancy to explore the influence of surface functional terminations and non-metallic center elements. Our findings demonstrate that surface functionalization significantly reduces the limiting potential by altering the rate-determining step. This change ranges from −1.24 V (Ti 2 NF 2) to −0.21 V (Ti 2 BSe 2), signifying the remarkable efficacy of modification of the surrounding environment of the exposed transition metal active center in promoting electrocatalytic performance. Detailed investigation of the charge density difference and orbital interaction reveals that the different NRR performance originates from the surface termination and non-metallic atoms regulate the electronic properties of the active Ti atoms. We also introduce the free energy change of *NNH 2 (Δ G *NNH2) as a descriptor to predict the performance of NRR, which exhibits satisfactory linear relationship with free energy change of different intermediates and displays favourable volcano plot with limiting potential. Moreover, we highlight the pivotal role of work function in tuning the energy barrier of the rate-determining step, which can be regulated through the surface modification of MXenes. Our study not only offers a comprehensive understanding of the crucial impact of surface modification on the catalytic activities of defective MXenes, but also provides a rational perspective for designing efficient NRR catalysts. [ABSTRACT FROM AUTHOR]

Synthesis of ammonia by electrochemical nitrogen reduction reaction (NRR) is a promising alternative to the Haber–Bosch process. However, it is commonly obstructed by the high activation energy. Here, we report the design and synthesis of an Al−Al bonded dual atomic catalyst stabilized within an amorphous nitrogen‐doped porous carbon matrix (Al2NC) with high NRR performance. The dual atomic Al2‐sites act synergistically to catalyze the complex multiple steps of NRR through adsorption and activation, enhancing the proton‐coupled electron transfer. This Al2NC catalyst exhibits a high Faradaic efficiency of 16.56±0.3 % with a yield rate of 29.22±1.2 μg h−1 mgcat−1. The dual atomic Al2NC catalyst shows long‐term repeatable, and stable NRR performance. This work presents an insight into the identification of synergistic dual atomic catalytic site and mechanistic pathway for the electrochemical conversion of N2 to NH3. [ABSTRACT FROM AUTHOR]

Ammonia is a vital chemical with numerous applications. Currently, the primary methods for generating the necessary reactants for ammonia production involve steam methane reforming (SMR) and cryogenic air separation unit (CASU), while the Haber-Bosch process converts these reactants into ammonia. However, the SMR process releases substantial amounts of CO 2 , making it imperative to employ an efficient and cost-effective CO 2 capture technology to mitigate emissions. This investigation focuses on evaluating the cryogenic CO 2 capture (CCC) process for blue ammonia production and provides a thorough economic analysis, estimating both the initial investment costs and operational expenses involved in producing blue ammonia. The results indicated that the CCC process can capture 90% of the CO 2 content in the flue gas emitted by the SMR, incurring an energy penalty of 0.724 M J e / k g C O 2 while capturing CO 2 in the liquid phase with purities exceeding 99.9%. In this case, the estimated CO 2 capture costs would be 18.05, 45.1, and 16.65 USD/ton in 2021, 2022, and 2023, respectively. This represents a 40% reduction compared to the CO 2 capture costs associated with conventional amine-based technology. The results of this study indicate that the annual electricity costs for ammonia production increase by 38.5% and 64.2% when employing the CCC and amine-based processes, respectively. This investigation employed an isothermal reactor for ammonia synthesis, using the heat from the exothermic reaction in a water ammonia absorption refrigeration cycle (ARC) to condense and purify ammonia. The results show that the ARC system can effectively condense ammonia at −6 °C, producing a liquid ammonia stream with 99.3% purity. This leads to a 95% reduction in power consumption compared to a vapor compression refrigeration cycle (VCRC). Consequently, this method has the potential to decrease the annual operational costs for ammonia production by 2.92%, 2.69%, and 3.13% in 2021, 2022, and 2023, respectively. This study indicated that the hydrogen production unit incurs the highest initial investment costs, as well as operating costs, in the blue ammonia production process, followed by CASU and the Haber-Bosch process. • The performance of the CCC process for blue NH 3 production was thoroughly evaluated. • The economic impacts of CCC process were compared with those of amine-based method. • An energy efficient method for condensation of NH 3 in Haber-Bosch process is given. • Natural gas costs mainly influence the operating costs of blue NH 3 production. [ABSTRACT FROM AUTHOR]

Urea is an indispensable nitrogen-containing organic compound in modern human life. However, the current industrial synthesis of urea involves ammonia, which is produced through the Haber-Bosch process under harsh reaction conditions, causing huge energy consumption and heavy environmental pollution. Electrochemical reduction of carbon dioxide (CO2) and nitrogenous species (N2, NOx x and NO) have achieved significant progress, offering a promising approach for the electrochemical C-N coupling to produce urea under ambient conditions. Urea synthesis driven by renewable electricity represents a suitable alternative to the traditional process, contributing to the goal of carbon neutrality and nitrogen cycles. However, challenges such as low yield rate, poor selectivity and unveiled reaction mechanisms still need to be addressed. This review provides a summary of the latest catalysts utilized in urea electrosynthesis, aiming to provide guidance and prospects for the development of highperformance catalysts. [ABSTRACT FROM AUTHOR]

The study aims to develop a process design and integration of a tri-generation system for simultaneous production of electricity using renewable resources, hydrogen (H2) and green ammonia (NH3). Ammonia being a vital raw material, is gaining recognition as a sustainable fuel, particularly for heavy transport and as a significant hydrogen energy carrier. The proposed integrated plant contains an alkaline water electrolysis system for hydrogen production, which is then consumed in the Haber-Bosch process for ammonia synthesis. The electricity required for electrolysis process is generated through renewable resources, specifically wind and solar energy. The energy is stored in form of molten salt through thermal energy storage technology. The process design includes detailed material and energy balances for water electrolysis and ammonia production units. Results obtained by rigorous design of equipment such a hydrogen and oxygen separators, heat exchanger, electrolyzer for hydrogen production and ammonia synthesis reactor highlight optimized operational and design parameters. The economic feasibility assessment of the process was made through cost estimation of key components, such as separators, heat exchanger, electrolyzer, compressor and tubular reactor. The findings obtained by this study highlight the potential of this tri-generation system in providing the sustainable solution for energy and climate change crisis, specifically in countries like Pakistan where renewable energy resources are present in abundance. [ABSTRACT FROM AUTHOR]

Ammonia, as the second most-produced chemical worldwide, serves diverse roles in the industrial and agricultural sectors. However, its conventional production via the Haber–Bosch process poses significant challenges, including high energy consumption and carbon dioxide emissions. In contrast, photocatalytic nitrogen (N2) fixation, utilizing solar energy with minimal emissions, offers a promising method for sustainable ammonia synthesis. Despite ongoing efforts, photocatalytic nitrogen fixation catalysts continue to encounter challenges such as inadequate N2 adsorption, limited light absorption, and rapid photocarrier recombination. This review explores how the electronic structure and surface characteristics of one-dimensional nanomaterials could mitigate these challenges, making them promising photocatalysts for N2 fixation. The review delves into the underlying photocatalytic mechanisms of nitrogen fixation and various synthesis methods for one-dimensional nanomaterials. Additionally, it highlights the role of the high surface area of one-dimensional nanomaterials in enhancing photocatalytic performance. A comparative analysis of the photocatalytic nitrogen fixation capabilities of different one-dimensional nanomaterials is provided. Lastly, the review offers insights into potential future advancements in photocatalytic nitrogen fixation. [ABSTRACT FROM AUTHOR]

The traditional Haber-Bosch process for the ammonia synthesis suffers from high energy consumption and severe pollution. Therefore, developing a clean and green synthetic process has been the current research focus. Electrochemical reduction is such a method for nitrogen fixation and ammonia formation, with the core technology lying in how to improve the yield and current efficiency by using proper electrochemical catalysts. Based on literature analysis and summarization, a review was made in this paper on the advances in the ruthenium-based catalysts for the ammonia synthesis, including the synthesis mechanisms from different nitrogen sources, the preparation and modification of ruthenium-based catalysts and their performance. Influence of the catalyst morphology and size on the performance as well as the synergistic effects among ruthenium metal, support, and co-catalysts were also explored, with an aim to provide new perspectives for understanding the ruthenium catalytic process of electrochemical reduction synthesis of ammonia. [ABSTRACT FROM AUTHOR]

The Haber–Bosch process is a cornerstone in the field of ammonia production and represents a decisive advance in industrial chemistry. This method, developed in the early 20th century, revolutionizes agriculture and enables the mass production of fertilizers. As the world strives for sustainable energy and environmental protection, alternative methods such as the photo/photoelectrocatalytic nitrogen reduction reaction (NRR) are gaining momentum. By using sunlight, electricity, or a combination of both, these approaches promise sustainable ammonia production with renewable energy sources and innovative materials. Researchers are trying to understand the underlying principles, mechanisms, and advances of these methods to overcome the challenges and optimize their effectiveness. This research is a step toward sustainable energy and agriculture, and offers a greener and more efficient way forward. This review looks at advances in sustainable ammonia production, particularly through photo‐ and photoelectrocatalytic NRRs. It examines the hurdles in implementing these methods and provides an overview of the fundamentals of nitrogen fixation and a comparison of current mechanisms. In addition, thermodynamic, theoretical, and computational studies of these processes are summarized. Various photocatalysts and photoelectrocatalysts used for ammonia production are also presented.

A glut of dinitrogen‐derived ammonia (NH3) over the past century has resulted in a heavily imbalanced nitrogen cycle and consequently, the large‐scale accumulation of reactive nitrogen such as nitrates in our ecosystems has led to detrimental environmental issues. Electrocatalytic upcycling of waste nitrogen back into NH3 holds promise in mitigating these environmental impacts and reducing reliance on the energy‐intensive Haber–Bosch process. Herein, we report a high‐performance electrolyzer using an ultrahigh alkalinity electrolyte, NaOH−KOH−H2O, for low‐cost NH3 electrosynthesis. At 3,000 mA/cm2, the device with a Fe−Cu−Ni ternary catalyst achieves an unprecedented faradaic efficiency (FE) of 92.5±1.5 % under a low cell voltage of 3.83 V; whereas at 1,000 mA/cm2, an FE of 96.5±4.8 % under a cell voltage of only 2.40 V was achieved. Techno‐economic analysis revealed that our device cuts the levelized cost of ammonia electrosynthesis by ~40 % ($30.68 for Fe−Cu−Ni vs. $48.53 for Ni foam per kmol‐NH3). The NaOH−KOH−H2O electrolyte together with the Fe−Cu−Ni ternary catalyst can enable the high‐throughput nitrate‐to‐ammonia applications for affordable and scalable real‐world wastewater treatments. [ABSTRACT FROM AUTHOR]

Ammonia (NH 3), as a high energy density chemical and hydrogen energy storage medium, has garnered significant interest in the realms of energy storage and catalysis. In contrast to the traditional Haber-Bosch process, the electrocatalysis nitrogen reduction reaction (eNRR) can synthesize green ammonia under mild reaction conditions. Based on density functional theory (DFT), the potential of 2D borophene supported transition metals as bimetallic atomic catalysts (BACs) in eNRR was investigated. Progressive screening through energy-oriented screening mechanism, Sc 2 B 12 , Ti 2 B 12 , V 2 B 12 and Zr 2 B 12 were identified as potential eNRR catalysts. Their complete reaction pathways and Gibbs free energy (ΔG) were further explored, and corresponding overpotentials were obtained. The results showed that overpotentials of the potential determining steps (PDS) of these catalysts were 0.34, 0.40, 0.39 and 0.13 V, respectively, demonstrating excellent eNRR catalytic activity and good selectivity. Cu 2 B 12 shows remarkable hydrogen evolution reaction (HER) catalytic activity with an overpotential (η) of only 0.05 V. The study also revealed that the catalytic activity of TM 2 B 12 is derived from its excellent conductivity, and the charge transmission enhances the catalyst activity of eNRR. Consequently, this study provides significant theoretical guidance and support for the synthesis of novel eNRR catalysts, and promotes further advancement in the field of catalysis. [Display omitted] • TM 2 B 12 confirms good thermodynamic, electrochemical and kinetic stability after energy-oriented screening process. • Four superior eNRR catalysts with overpotential ranging from 0.13 to 0.40 V were discovered. • Cu 2 B 12 showed remarkable HER catalytic activity with an overpotential of only 0.05 V. • Catalytic activity of TM 2 B 12 originates from its excellent conductivity and charge transfer improves catalytic activity. [ABSTRACT FROM AUTHOR]

In contrast to the energy-consuming Haber–Bosch process, ammonia synthesis by electrocatalysis under ambient conditions is an efficient and environmentally friendly method. In this work, through first principles calculations, the potential of four dual-atom FeTM (TM = Fe, Mo, Co, and V) anchored graphyne (FeTM@GY) as efficient nitrogen reduction reaction (NRR) catalysts is systematically investigated. Among them, FeMo@GY is the most promising, with excellent NRR catalytic activity, high ability to suppress the competing hydrogen evolution reaction (HER), and good stability. Moreover, NRR prefers the maximum pathway with the calculated onset potentials of −0.27 V for FeMo@GY. This work not only suggests that FeMo@GY holds great promise as an efficient, low-cost, and stable dual-atom catalyst for NRR but also further provides a guiding idea for the design of efficient NRR catalysts. [ABSTRACT FROM AUTHOR]

The electrochemical nitrogen reduction reaction (NRR) has emerged as a sustainable and environmental–friendly alternative for ammonia synthesis compared with conventional Haber–Bosch process. However, considerable challenges persist in developing cost-effective catalysts for NRR. Herein, Cu 7 · 2 S 4 /C was synthesized using a continuous microchannel reactor followed by carbonization sulfurization at 600 °C. The as-prepared Cu 7 · 2 S 4 /C catalyst, featuring abundant sulfur vacancies, exhibited outstanding electrochemical performance for NRR, achieving an ammonia yield of 52 μg h − 1 mg cat. − 1 and Faraday efficiency of 32.2%. In addition, density functional theory calculations suggest that sulfur vacancies contribute to a decrease in Gibbs free energy during N 2 -activated hydrogenation, thereby facilitating adsorption of N 2 and formation of Cu–N bonds at catalytic active centers. This study introduces a novel strategy for synthesizing economical and efficient NRR electrocatalysts based on transition metal-based metal–organic frameworks. [Display omitted] • Cu-BTC was successfully synthesized using a continuous microchannel reactor. • BTC-derived Cu 7 · 2 S 4 /C with sulfur vacancy exhibited enhanced nitrogen reduction reaction performance for ammonia synthesis. • Cu 7.2 S 4 /C facilitated N 2 chemisorption and reduced Gibbs free energy for N 2 -activated hydrogenation. [ABSTRACT FROM AUTHOR]

The conventional ammonia production process using the Haber-Bosch (H-B) method is highly efficient but necessitates severe reaction conditions with a large energy consumption. Meanwhile, a significant CO 2 emission are generated due to the acquisition of H 2. This study proposed a system combined the non-thermal plasma and fluidized catalysts with the water vapor as the green feedstock for high-efficiency ammonia synthesis. Results reveal that bimetallic Co-Ni supported catalysts on the MgO carrier exhibit notably higher NH 3 formation rates than single-component metal-supported catalysts and no catalysts. The highest NH 3 formation rate, achieved with a 4 wt% catalysts loading, reached 12.07 μmol g−1h−1 (specific energy input of 2.15 kJ L−1, energy efficiency of 6.57 mg kW−1h−1). A synergistic effect between the fluidized catalysts and the plasma was observed. It greatly improves ammonia yield and provides a new platform for sustainable ammonia synthesis. [Display omitted] • A plasma-coupled fluidized catalysts for ammonia synthesis is proposed. • The synergistic effect of DBD plasma and fluidized catalysts is explored in depth. • The green ammonia synthesis process is based on N 2 and H 2 O as feedstock. [ABSTRACT FROM AUTHOR]

Production of ammonia (NH3) by electrocatalytic reduction of nitrate (NO3RR) not only eliminates harmful pollution, but also provides a way to reduce the energy consumption associated with predominated Haber‐Bosch process. However, realization of this process still faces many challenges because of the complexity of the reaction mechanism. Here we investigated the catalytic activity and selectivity of a series of graphdiyne supported single atom catalysts (SACs), namely TM/GDY, for the reduction of NO3−$$ {\mathrm{O}}_3^{-} $$ to NH3 by first‐principles calculations. Among the 10 SACs studied, Fe/GDY was found to have good catalytic performance, consistent with the fact that the Fe‐doped GDY molecular layer was located near the top of the volcano plot, with a reaction limit potential of −0.44 V and showed excellent selectivity in inhibiting the competitive hydrogen evolution reaction (HER). The formation of the by‐products NO2, NO, N2O and N2 on Fe/GDY requires a considerable energy barrier, which ensures high selectivity. Furthermore, detailed electronic property analyses indicate that the GDY can work as an electron repository to effectively balance the charge transfers during the reaction process. This study not only offers an eligible NO3RR electrocatalyst but also provides an atomic understanding of the mechanisms of the NO3RR process behind. [ABSTRACT FROM AUTHOR]

Ammonia (NH3) is a vital chemical for modern human society. It is conventionally produced by the energy‐ and emission‐intensive Haber–Bosch process. Alternatively, sustainable NH3 production from renewable electricity‐driven electrolyzers has emerged as a promising route. Particularly, NH3 synthesis from nitrate (NO3−), a common pollutant in water and soil, by the nitrate reduction reaction (NO3RR) has drawn wide attention. Among various catalysts demonstrated recently, copper (Cu)‐based catalysts have been recognized as attractive candidates due to their availability, good activity, high NH3 selectivity, and facile reaction kinetics. In this review, the recent progress of Cu‐based NO3RR catalysts from the reaction mechanistic fundamentals to various catalyst design strategies, aiming at providing an on‐time summary, is summarized, and perspectives that can guide the rational and on‐demand design of Cu‐ and other earth‐abundant metal‐based catalysts for selective NO3RR toward sustainable NH3 production are elucidated. [ABSTRACT FROM AUTHOR]

Electrochemical nitrate reduction reaction (NO3RR) towards ammonia, as an emerging and appealing technology alternative to the energy-intensive Haber–Bosch process and inefficient nitrogen reduction reaction, has recently aroused wide concern and research. However, the current research of the NO3RR towards ammonia lacks the overall performance comparison of various electrocatalysts. Given this, we here make a comparison of 12 common transition metal oxide catalysts for the NO3RR under a high cathodic current density of 0.25 A·cm−2, wherein Co3O4 catalyst displays the highest ammonia Faradaic efficiency (85.15%) and moderate activity (ca. −0.25 V vs. reversible hydrogen electrode). Other external factors, such as nitrate concentrations in the electrolyte and applied potential ranges, have also been specifically investigated for the NO3RR. [ABSTRACT FROM AUTHOR]

Ammonia is pivotal to various chemical industries, which is produced using the Haber-Bosch process. This process requires harsh conditions (e.g., 20.0 MPa and (500–600)°C) to generate ammonia and thus, is an energy intensive process. The growing consensus is to mild the conditions for ammonia generation. Herein, we demonstrate the use of hydride to increase the activity of molybdenum carbonitride (MCN). YH@MCN (95:5, w/w) generates ammonia at a rate of 448 μ m o l g − 1 h − 1 at 255 °C and 0.1 MPa. To address the stability issue of hydride, we incorporate iron. The experiment demonstrates two-fold rates for such catalyst, comparing MCN alone. The activation energy (19.73kJmol-1) for YFeH@MCN is considerably low, owing to the electron transfer from YH to MCN that facilitates nitrogen dissociation. Hence, the use of distinct sites for easy dissociation of nitrogen molecules, and the synergy between them, results in an activity that exceeds of conventional molybdenum and iron-based catalysts, and is comparable to ruthenium-based catalysts. Our results illustrate the potential of using synergistic multiple active sites in catalysts, and introduce a design concept for ammonia synthesis catalysts, using readily available elements. • Low-temperature ammonia synthesis is performed using hydrides. • Hydride promotes catalytic activity of molybdenum carbonitride. • Hydrogen storage capacity of yttrium mixed with iron is examined. • YH@MCN generates ammonia at a rate of 448 μ m o l g − 1 h − 1 at 255 °C and 0.1 MPa. • Low activation energy (19.73kJmol-1) infers transfer of electrons from YH to MCN. [ABSTRACT FROM AUTHOR]

Ammonia, a vital component in the synthesis of fertilizers, plastics, and explosives, is traditionally produced via the energy‐intensive and environmentally detrimental Haber–Bosch process. Given its considerable energy consumption and significant greenhouse gas emissions, there is a growing shift toward electrocatalytic ammonia synthesis as an eco‐friendly alternative. However, developing efficient electrocatalysts capable of achieving high selectivity, Faraday efficiency, and yield under ambient conditions remains a significant challenge. This review delves into the decades‐long research into electrocatalytic ammonia synthesis, highlighting the evolution of fundamental principles, theoretical descriptors, and reaction mechanisms. An in‐depth analysis of the nitrogen reduction reaction (NRR) and nitrate reduction reaction (NitRR) is provided, with a focus on their electrocatalysts. Additionally, the theories behind electrocatalyst design for ammonia synthesis are examined, including the Gibbs free energy approach, Sabatier principle, d‐band center theory, and orbital spin states. The review culminates in a comprehensive overview of the current challenges and prospective future directions in electrocatalyst development for NRR and NitRR, paving the way for more sustainable methods of ammonia production. [ABSTRACT FROM AUTHOR]

In contrast to the energy‐intensive Haber‐Bosch process, the electroreduction of nitrate to ammonia presents a promising alternative. In this work, the Ni2P/Pd6P nanorods (named NiPdP‐NR) are successfully synthesized by using a simple phosphating process with NiIIPdII‐dimethylglyoxime complex (NiIIPdII‐DMG) nanorods as the precursor. Density functional theory calculations and electrochemical experiments prove that the introduction of Pd facilitates hydrogen spillover from Pd to Ni2P modulates the surface electronic structures, and therefore improves the catalytic kinetics of nitrate reduction ultimately. According to the dynamic experiment, the as‐prepared NiPdP‐NR shows high nitrate conversion efficiency (90.6%), selectivity of NH3 (93.4%), high Faradic efficiency (92.6%), and NH3 yield rate (0.908 mmol h−1 mgcat−1) for the nitrate reduction. [ABSTRACT FROM AUTHOR]

Ammonia (NH3) is a critical chemical for fertilizer production and a potential future energy carrier within a sustainable hydrogen economy. The industrial Haber–Bosch process, though effective, operates under harsh conditions due to the high thermodynamic stability of the nitrogen molecule (N2). This motivates the search for alternative catalysts that facilitate ammonia synthesis at milder temperatures and pressures. Theoretical and experimental studies suggest that circumventing the trade-off between N–N activation and subsequent NHx hydrogenation, governed by the Brønsted–Evans–Polanyi (BEP) relationship, is key to achieving this goal. Recent studies indicate metal phosphides as promising catalyst materials. In this work, a comprehensive density functional theory (DFT) study comparing the mechanisms and potential reaction pathways for ammonia synthesis on Fe(110) and Fe2P(001) is presented. The results reveal substantial differences in the adsorption strengths of NHx intermediates, with Fe2P(001) exhibiting weaker binding compared to Fe(110). For N–N bond cleavage, multiple competing pathways become viable on Fe2P(001), including routes involving the pre-hydrogenation of adsorbed N2 (e.g., through *NNH*). Analysis of DFT-derived turnover rates as a function of hydrogen pressure (H2) highlights the increased importance of these hydrogenated intermediates on Fe2P(001) compared to Fe(110) where direct N2 dissociation dominates. These findings suggest that phosphorus incorporation modifies the ammonia synthesis mechanism, offering alternative pathways that may circumvent the limitations of traditional transition metal catalysts. This work provides theoretical insights for the rational design of Fe-based catalysts and motivates further exploration of phosphide-based materials for sustainable ammonia production. [ABSTRACT FROM AUTHOR]

The present paper investigates the energy efficiency of ammonia production by a freely oscillating microbubble placed in an infinite domain of liquid. The spherical bubble initially contains a mixture of nitrogen and hydrogen. The bubble is expanded from its equilibrium size to a specific maximum radius via an isothermal expansion. The work needed to expand the bubble is its potential energy calculated by the sum of the work done by the internal gas, the work needed to displace the mass of the surrounding liquid, and the work needed to increase the area of the bubble against the surface tension. During the radial pulsation of the freely oscillating bubble, the internal temperature can reach several thousands of degrees of Kelvin inducing chemical reactions. The chemical yield is computed by solving a set of ordinary differential equations describing the radial dynamics of the bubble (Keller--Miksis equations), the temporal evolution of the internal temperature (first law of thermodynamics), and the concentration of the chemical species (reaction mechanism). The control parameters during the simulations were the equilibrium bubble size, initial expansion ratio, ambient pressure, and the initial concentration ratio of nitrogen and hydrogen. In the best-case scenario, the energy requirement in terms of GJ/t is 6.8 times higher than the best available facility of the Haber--Bosch process (assuming that the hydrogen is produced via the electrolysis of water). [ABSTRACT FROM AUTHOR]