Defect-rich fluorographene nanosheets for artificial N2 fixation under ambient conditions

Engineering hydrophobic-aerophilic interfaces to boost N2 diffusion and reduction through functionalization of fluorine in second coordination spheres

Ammonia is a crucial biochemical raw material for nitrogen containing fertilizers and a hydrogen energy carrier obtained from renewable energy sources. Electrocatalytic ammonia synthesis is a renewable and less-energy intensive way as compared to the conventional Haber-Bosch process. The electrochemical nitrogen reduction reaction (eNRR) is sluggish, primarily due to the deceleration by slow N2 diffusion, giving rise to competitive hydrogen evolution reaction (HER). Herein, we have engineered a catalyst to have hydrophobic and aerophilic nature via fluorinated copper phthalocyanine (F-CuPc) grafted with graphene to form a hybrid electrocatalyst, F-CuPc-G. The chemically functionalized fluorine moieties are present in the second coordination sphere, where it forms a three-phase interface. The hydrophobic layer of the catalyst fosters the diffusion of N2 molecules and the aerophilic characteristic helps N2 adsorption, which can effectively suppress the HER. The active metal center is present in the primary sphere available for the NRR with a viable amount of H+ to achieve a substantially high faradaic efficiency (FE) of 49.3% at -0.3 V vs. RHE. DFT calculations were performed to find out the rate determining step and to explore the full energy pathway. A DFT study indicates that the NRR process follows an alternating pathway, which was further supported by an in situ FTIR study by isolating the intermediates. This work provides insights into designing a catalyst with hydrophobic moieties in the second coordination sphere together with the aerophilic nature of the catalyst that helps to improve the overall FE of the NRR by eliminating the HER.

Efficient asymmetrical silicon-metal dimer electrocatalysts for the nitrogen reduction reaction

The electrocatalytic nitrogen reduction reaction (ENRR) has been regarded as an eco-friendly and feasible substitute for the Haber-Bosch method. Identifying the effective catalysts for the ENRR is an extremely important prerequisite but challenging. Herein, asymmetrical silicon-metal dimer catalysts doped into g-C₃N₄ nanosheets with nitrogen vacancies (SiM@C₃N₄) were designed to address nitrogen activation and reduction. The concept catalysts of SiM@C₃N₄ can combine the advantages of silicon-based and metal-based catalysts during the ENRR. Among the catalysts investigated, SiMo@C₃N₄ and SiRu@C₃N₄ exhibited the highest activities towards the ENRR with ultra-low onset potentials of -0.20 and -0.39 V; meanwhile, they suppressed the competing hydrogen evolution reaction (HER) due to the relative difficulty in releasing hydrogen. Additionally, SiRu@C₃N₄ is demonstrated to possess strong hydrophobicity, which is greatly beneficial to the production of ammonia. This research provides insights into asymmetrical silicon-metal dimer catalysts and reveals a new method for developing dual-atom electrocatalysts. This asymmetrical dimer strategy can be applied in other electrocatalytic reactions for energy conversion.

Facile and controllable preparation of carbon microsphere for electro-driven nitrogen reduction: Accommodating nitrogen doping with hierarchical porous structure

Driven by sustainable electricity, electrochemical nitrogen fixation under ambient conditions is considered as a promising strategy to generate low-concentrated NH₃/NH₄⁺. Under the principle of doping and porous engineering, nitrogen-doped carbon microsphere with hierarchical pores (NC-HP) is fabricated via pyrolyzing polymer microsphere. Hierarchical structure with macro-, meso- and micropores is obtained by assembling melamine/phenol-formaldehyde oligomers in Pickering droplets, with the assistance of triblock copolymer Pluronic F127. The regularity of mesopores is strongly affected by melamine to phenol mass ratio. For NC-HP, nitrogen content (N-content) in the carbon matrix can reach as high as 19.1 wt%, yet trade-off effect is observed between N-content and regularity of mesopores. As consequence, NC-HP-3 with N-content of 15.6 wt% and distinct mesopores exhibits the highest catalytic performance. At -0.5 V vs. RHE, NH₃/NH₄⁺ production rate and Faradaic efficiency (FE) value reach 15.6 μg∙mg_cat.^-1∙h^-1 and 15.5%, respectively. It shows excellent recyclability, and no degradations are observed with respect to morphology and porous structure. In this hierarchical porous structure, mesopores are expected to facilitate mass transfer for both electrolyte ions and nitrogen, and hence catalytic active sites (e.g. pyrrolic- and pyridinic-N species) in hierarchically mutually connected pores can be well utilized.

Effect of local coordination on catalytic activities and selectivities of Fe-based catalysts for N2 reduction

Electrochemical reduction of nitrogen is considered as a promising route for achieving green and sustainable ammonia synthesis at ambient conditions. Transition metal atom loaded on N-doped graphene is commonly used...

Single boron modulated Graphdiyne nanosheet for efficient electrochemical nitrogen fixation: A First-Principles Study

The electroreduction of dinitrogen (N2) is a promising alternative approach for ammonia synthesis under mild conditions. In this work, metal-free electrocatalysts using a single boron atom doped into graphdiyne (GDY)...

Insight into the Reactivity of Carbon Structures for Nitrogen Reduction Reaction

Graphene-based structures have been widely reported as promising metal-free catalysts for nitrogen reduction reaction. To explain the reactivity origin, various structures have been proposed and debated, including defects, functional groups, and doped heteroatoms. This computational work demonstrates that these structures may evolve from one to another under electrochemical conditions, generating weakly coordinated carbons, which have been identified as the active sites for N₂ adsorption and activation.

Nanocarbon for Energy Material Applications: N2 Reduction Reaction

Nanocarbons are an important class of energy materials and one relevant application is for the nitrogen reduction reaction, i.e., the direct synthesis of NH₃ from N₂ and H₂ O via photo- and electrocatalytic approaches. Ammonia is also a valuable energy or hydrogen vector. This perspective paper analyses developments in the field, limiting discussion to nanocarbon-based electrodes. These aspects are discussed: i) active sites related to charge density differences on C atoms associated to defects/strains, ii) doping with heteroatoms, iii) introduction of isolated metal ions, iv) creation and in situ dynamics of metal oxide(hydroxide)/nanocarbon boundaries, and v) nanocarbon characteristics to control the interface. Discussion is focused on the performances and mechanistic aspects. Aim is not a systematic state-of-the-art report but to highlight the need to use a different perspective in studying this challenging reaction by using selected papers. Notwithstanding the large differences in the proposed nature of the active sites, fall all within a restricted range of performances, far from the targets. A holistic approach is emphasized to make a breakthrough advance.

Rational Design of Graphene Derivatives for Electrochemical Reduction of Nitrogen to Ammonia

The conversion of nitrogen to ammonia offers a sustainable and environmentally friendly approach for producing precursors for fertilizers and efficient energy carriers. Owing to the large energy density and significant gravimetric hydrogen content, NH₃ is considered an apt next-generation energy carrier and liquid fuel. However, the low conversion efficiency and slow production of ammonia through the nitrogen reduction reaction (NRR) are currently bottlenecks, making it an unviable alternative to the traditional Haber-Bosch process for ammonia production. The rational design and engineering of catalysts (both photo- and electro-) represent a crucial challenge for improving the efficiency and exploiting the full capability of the NRR. In the present review, we highlight recent progress in the development of graphene-based systems and graphene derivatives as catalysts for the NRR. Initially, the history, fundamental mechanism, and importance of the NRR to produce ammonia are briefly discussed. We also outline how surface functionalization, defects, and hybrid structures (single-atom/multiatom as well as composites) affect the N₂ conversion efficiency. The potential of graphene and graphene derivatives as NRR catalysts is highlighted using pertinent examples from theoretical simulations as well as machine learning based performance predictive methods. The review is concluded by identifying the crucial advantages, drawbacks, and challenges associated with principal scientific and technological breakthroughs in ambient catalytic NRR.

Emerging two-dimensional nanomaterials for electrochemical nitrogen reduction

Ammonia (NH₃) is essential to serve as the biological building blocks for maintaining organism function, and as the indispensable nitrogenous fertilizers for increasing the yield of nutritious crops. The current Haber-Bosch process for industrial NH₃ production is highly energy- and capital-intensive. In light of this, the electroreduction of nitrogen (N₂) into valuable NH₃, as an alternative, offers a sustainable pathway for the Haber-Bosch transition, because it utilizes renewable electricity and operates under ambient conditions. Identifying highly efficient electrocatalysts remains the priority in the electrochemical nitrogen reduction reaction (NRR), marking superior selectivity, activity, and stability. Two-dimensional (2D) nanomaterials with sufficient exposed active sites, high specific surface area, good conductivity, rich surface defects, and easily tunable electronic properties hold great promise for the adsorption and activation of nitrogen towards sustainable NRR. Therefore, this Review focuses on the fundamental principles and the key metrics being pursued in NRR. Based on the fundamental understanding, the recent efforts devoted to engineering protocols for constructing 2D electrocatalysts towards NRR are presented. Then, the state-of-the-art 2D electrocatalysts for N₂ reduction to NH₃ are summarized, aiming at providing a comprehensive overview of the structure-performance relationships of 2D electrocatalysts towards NRR. Finally, we propose the challenges and future outlook in this prospective area.

MoS2 -Based Catalysts for N2 Electroreduction to NH3 - An Overview of MoS2 Optimization Strategies

The nitrogen reduction reaction (NRR) has become an ideal alternative to the Haber-Bosch process, as NRR possesses, among others, the advantage of operating under ambient conditions and saving energy consumption. The key to efficient NRR is to find a suitable electrocatalyst, which helps to break the strong N≡N bond and improves the reaction selectivity. Molybdenum disulfide (MoS2 ) as an emerging layered two-dimensional material has attracted a mass of attention in various fields. In this minireview, we summarize the optimization strategies of MoS2 -based catalysts which have been developed to improve the weak NRR activity of primitive MoS2 . Some theoretical predictions have also been summarized, which can provide direction for optimizing NRR activity of future MoS2 -based materials. Finally, an outlook about the optimization of MoS2 -based catalysts used in electrochemical N2 fixation are given.

Double boron atom-doped graphdiynes as efficient metal-free electrocatalysts for nitrogen reduction into ammonia: a first-principles study

The electroreduction of dinitrogen (N₂) is an attractive method for ambient ammonia (NH₃) synthesis. In this work, double boron atom-anchored two-dimensional (2D) graphdiyne (GDY-2B) electrocatalysts have been designed and examined for the N₂ reduction reaction (NRR) by density functional theory computations. Our calculations revealed that double boron atoms can be strongly embedded in a graphdiyne monolayer. In particular, configuration GDY-2B(S₂S₂') with two boron atoms substituting two equivalent sp-carbon atoms of diacetylene linkages exhibits excellent catalytic performance for reducing N₂, with an extremely low overpotential of 0.12 V. The "pull-pull" mechanism imposed by doped double boron atoms is responsible for the magnificent effect of N₂ activation. Besides, the competitive reaction of the hydrogen evolution reaction (HER) is suppressed owing to a large ΔG_H* value of -1.25 eV. Based on these results, our study provides useful guidelines for designing effective double atomic catalysts (DACs) based on nonmetal 2D nanosheets for effective electrochemical reduction reactions.

Halogen Functionalization in the 2D Material Flatland: Strategies, Properties, and Applications

Given the electronegativity and bonding environment of halogen elements, halogenation (i.e., fluorination, chlorination, bromination, and iodination) serves as a versatile strategy for chemical modifications of materials. The combination of halogens and 2D materials has triggered extensive interests since the first report on graphene fluorination in 2008. Subsequently, scholars consistently conduct pre-, in-process, or posthalogenation modifications of emerging 2D materials to achieve desired properties and broad device applications. They also continuously explore the role of halogens in 2D material functionalization. The multiple advantages introduced by halogen decoration make 2D materials outstanding from each subclass. In this review, an overall retrospect is provided on the research advances in the area of 2D material halogenation, including experimental halogenation strategies, halogen-triggered novel physics and properties, and advanced applications across the studied objects. Future research directions in this area are also proposed.

High temperature induced S vacancies in natural molybdenite for robust electrocatalytic nitrogen reduction

Defect engineering is an important strategy to regulate electronic structure of electrocatalysts for electrochemical N₂ fixation, aiming at improving the electron state density and enhancing the adsorption and activation of inert N₂. In this paper, a high-temperature strategy to anneal the natural molybdenite under Ar atmosphere was developed, and the as-obtained molybdenite with S vacancies boosted a high activity for N₂ reduction reaction. In 0.1 M HCl, the catalyst annealed at 800 °C exhibits a high Faradic efficiency of 17.9% and a NH₃ yield of 23.38 μg h^-1 mg^-1_cat. at -0.35 V versus reversible hydrogen electrode, two times higher than that of the pristine molybdenite. The facile one-step annealing method introduces the defects (e.g., S vacancies) in the surface of the natural molybdenite particles to prepare catalysts for generating ammonia by reducing nitrogen at room temperature under ordinary pressure, promoting the development of low-carbon economic prospect.

Preparation of nitrogen self-doped hierarchical porous carbon with rapid-freezing support for cooperative pollutant adsorption and catalytic oxidation of persulfate

Herein, we report a method to synthesize nitrogen self-doped hierarchical porous carbon materials derived from chitosan. This method uses potassium hydroxide (KOH) activation and rapid-freezing technology. The catalyst (CA-900Q 1-1) obtained after rapid-freezing and KOH activation treatment show excellent persulfate activation ability. It can remove 20 mg bisphenol A (BPA) within 10 min better than traditional metal oxidate and nanomaterials. In the aquatic environment, CA-900Q 1-1 has a high resistance to inorganic anions. CA-900Q 1-1, possessing a high proportion of graphitic nitrogen, provides a sufficient number of active sites for persulfate activation. In addition, the catalyst yielded sizeable specific surface areas (SSAs) (1756.1 m²/g) and a hierarchical pore structure, which helps to improve the mass transfer in the carbon framework. The efficient adsorption of pollutants by the catalyst shortens the time required for target organic molecules to migrate to the catalyst surface and hierarchical pore structure. Furthermore, the catalyst has excellent electrical conductivity (R = 1.73 Ω), which enables pollutants adsorbed on the catalyst surface to transfer electrons to the persulfate through the N-doped sp²-hybrid carbon network faster.

Electrochemical nitrogen reduction: recent progress and prospects

Ammonia is one of the most useful chemicals for the fertilizer industry and is also promising as an important energy carrier for fuel cell application, and is currently mostly produced by the traditional Haber-Bosch process under high temperature and pressure conditions. This energy-intensive process is detrimental to the environment due to the dependence on fossil fuels and the emission of significant greenhouse gases (such as CO2). Ammonia production via the electrochemical nitrogen reduction reaction (ENRR) has been recognized as a green sustainable alternative to the Haber-Bosch process in recent years. Current ENRR research mainly focuses on the catalyst for ammonia selective production and the enhancement of faradaic efficiency at high current density; however, these have not been explored well due to the unavailability of highly efficient and cheap catalysts. Herein, this review provides information on the ENRR process along with (i) theoretical background, (ii) experimental methodology of the electrocatalytic process and (iii) computational screening of promising catalysts. The impact of active sites and defects on the activity, selectivity, and stability of the catalysts is deeply understood. Furthermore, we demonstrate the mechanistic understanding of the ENRR process on the surface of catalysts, with the aim of boosting the improvement of the ENRR activities. The ammonia detection methods are also summarized along with thorough discussion of control experiments. Finally, this review highlights prevailing problems in existing ENRR methods of ammonia production along with technical advancements proposed to address these issues and concludes with comments on opportunities and future directions of the ENRR process.

High-performance ammonia fixation electrocatalyzed by ReS2 nanosheet array

The industrial-scale NH₃ production still heavily depends on the Haber–Bosch process, which not only demands high energy consumption but also emits a large amount of CO₂.

Anchoring Au(111) on a Bismuth Sulfide Nanorod: Boosting the Artificial Electrocatalytic Nitrogen Reduction Reaction under Ambient Conditions

Electrocatalytic nitrogen reduction reaction (NRR), as a green and sustainable method for ammonia synthesis, has become one of the candidates to substitute industrial Haber-Bosch ammonia synthesis in the near future. In this work, gold nanoparticles (Au NPs) were successfully anchored on bismuth sulfide nanorods (Bi₂S₃ NRs), which acted as highly efficient electrocatalytic NRR catalysts. The N-philic nature of Bi and the unique mutual coordination of Au-S-Bi can greatly promote the nitrogen adsorption and form the intermediate product N₂H*, achieving a boosted improvement in the NRR activity through a continuous hydrogenation reaction. Definitely, the as-synthesized Au(111)@Bi₂S₃ nanorod catalyst exhibits an excellent NH₃ generation rate of 45.57 μg h^-1 mg_cat.^-1 with a faradic efficiency of 3.10% at -0.8 V vs reversible hydrogen electrode. High stability and reproducibility are also demonstrated throughout the electrocatalytic NRR process. Density functional theory calculations were performed to further understand the NRR catalytic mechanism on the Au(111)@Bi₂S₃ nanorods catalyst.

Two dimensional electrocatalyst engineering via heteroatom doping for electrocatalytic nitrogen reduction

The electrocatalytic N₂ reduction reaction (eNRR) - which can occur under ambient conditions with renewable energy input - became a promising synthetic pathway for ammonia (NH₃) and has attracted growing attention in the past few years. Some achievements have been made in the eNRR; however, there remain significant challenges to realize satisfactory NH₃ production. Therefore, the rational design of highly efficient and durable eNRR catalysts with N[triple bond, length as m-dash]N bond activating and breaking ability is highly desirable. Two-dimensional (2D) materials have shown great potential in electrocatalysis for energy conversion and storage. Although most 2D materials are inactive toward the eNRR, they can be activated by various modification methods. Heteroatom doping engineering can impact the charge distribution and spin states on catalytic sites, therefore accelerating the dinitrogen adsorption and protonation process. This review summarises the recent research progress of heteroatom-doped 2D materials, including carbon, molybdenum disulfide (MoS₂) and metal carbides (MXenes), for the eNRR. In addition, some existing opportunities and future research directions in electrocatalytic nitrogen fixation for ammonia production are discussed.

Exploration and Investigation of Periodic Elements for Electrocatalytic Nitrogen Reduction

High demand for green ecosystems has urged the human community to reconsider and revamp the traditional way of synthesis of several compounds. Ammonia (NH₃ ) is one such compound whose applications have been extended from fertilizers to explosives and is still being synthesized using the high energy inhaling Haber-Bosch process. Carbon free electrocatalytic nitrogen reduction reaction (NRR) is considered as a potential replacement for the Haber-Bosch method. However, it has few limitations such as low N₂ adsorption, selectivity (competitive HER reactions), low yield rate etc. Since it is at the early stage, tremendous efforts have been devoted in understanding the reaction mechanism and screening of the electrocatalysts and electrolytes. In this review, the electrocatalysts are classified based on the periodic table with heat maps of Faraday efficiency and yield rate of NH₃ in NRR and their electrocatalytic properties toward NRR are discussed. Also, the activity of each element is discussed and short tables and concise graphs are provided to enable the researchers to understand recent progress on each element. At the end, a perspective is provided on countering the current challenges in NRR. This review may act as handbook for basic NRR understandings, recent progress in NRR, and the design and development of advanced electrocatalysts and systems.

A boron-decorated melon-based carbon nitride as a metal-free photocatalyst for N2 fixation: a DFT study

On the basis of the electron "acceptance-donation" concept, a boron decorated melon-based carbon nitride (CN) is studied as a metal-free photocatalyst to efficiently reduce N2 to NH3 under visible light irradiation. The results revealed that a boron-interstitial (Bint)-decorated melon-based CN has an outstanding N2 reduction capacity through the enzymatic mechanism with a rather low overpotential (0.32 V). The excellent efficiency and selectivity of Bint-decorated melon-based CN in N2 reduction reaction (NRR) are attributed to the concentrated spin polarization on the B atom, the significant enhancement of visible and infrared light absorption, and the effective inhibition of the competitive hydrogen evolution reaction (HER). Importantly, B-doped melon-based CN has been successfully synthesized in the experiments, so obtaining Bint-decorated melon is promising, while proton transfer from the -NH2 group in CN to the B atom surely will affect the functionality of the catalyst through deactivation of the N2 adsorption site. Our study provides a novel single atom metal-free photocatalyst with high efficiency for NRR, which is conducive to the sustainable synthesis of ammonia.

Current Progress of Electrocatalysts for Ammonia Synthesis Through Electrochemical Nitrogen Reduction Under Ambient Conditions

Ammonia, one of the most important chemicals and carbon-free energy carriers, is mainly produced by the traditional Haber-Bosch process operated at high pressure and temperature, which results in massive energy consumption and CO2 emissions. Alternatively, the electrocatalytic nitrogen reduction reaction to synthesize NH3 under ambient conditions using renewable energy has recently attracted significant attention. However, the competing hydrogen evolution reaction (HER) significantly reduces the faradaic efficiency and NH3 production rate. The design of high-performance electrocatalysts with the suppression of the HER for N2 reduction to NH3 under ambient conditions is a crucial consideration for the development of electrocatalytic NH3 synthesis with high FE and NH3 production rate. Five kinds of recently developed electrocatalysts classified by their chemical compositions are summarized, with particular emphasis on the relationship between their optimal electrocatalytic conditions and NH3 production performance. Conclusions and perspectives are provided for the future design of high-performance electrocatalysts for electrocatalytic NH3 production. The Review can give practical guidance for the design of effective electrocatalysts with high FE and NH3 production rates.

Identifying the Active Site on Graphene Oxide Nanosheets for Ambient Electrocatalytic Nitrogen Reduction

Identifying the active sites on graphene oxide (GO) nanosheets is of great importance. In situ electroreduction at different potentials is applied to control the oxygenated groups on GO surfaces. Both experiments and theoretical calculations suggest the C═O group is critical for N₂ adsorption and activation, guaranteeing the ambient electrocatalytic N₂ reduction.

A highly selective and active metal-free catalyst for ammonia production

We report a facile surface-induced method for the in situ growth of single-/few-layered crystalline fluorographdiyne film on the surface of carbon fibers (cFGDY). The crystallized structure of cFGDY was directly confirmed by the scanning/transmission electron microscopy (SEM/TEM), high-resolution TEM (HRTEM) and computer simulation, selected area electron diffraction (SAED), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. cFGDY showed a 9-fold stacking mode. Our results show that cFGDY is a metal-free electrocatalyst with unique structure and excellent performance for ammonia production from nitrogen and water efficiently at room temperature and ambient pressure, achieving a high NH₃ production rate and Faraday efficiency in neutral conditions. This work provides an efficient catalyst system with determined chemical and electronic structures for highly selective and active nitrogen reduction, serving as a promising platform towards the development of novel metal-free catalysts.

Ambient Ammonia Electrosynthesis: Current Status, Challenges, and Perspectives

Ammonia (NH₃ ) electrosynthesis from atmospheric nitrogen (N₂ ) and water is emerging as a promising alternative to the energy-intensive Haber-Bosch process; however, such a process is difficult to perform due to the inherent inertness of N₂ molecules together with low solubility in aqueous solutions. Although many active electrocatalysts have been used to electrocatalyze the N₂ reduction reaction (NRR), unsatisfactory NH₃ yields and lower Faraday efficiency are still far from practical industrial production, and thus, considerable research efforts are being devoted to address these problems. Nevertheless, most reports still mainly focus on the preparation of electrocatalysts and largely ignore a summary of optimization-modification strategies for the NRR. In this review, a general introduction to the NRR mechanism is presented to provide a reasonable guide for the design of highly active catalysts. Then, four categories of NRR electrocatalysts, according to chemical compositions, are surveyed, as well as several strategies for promoting the catalytic activity and efficiency. Later, strategies for developing efficient N₂ fixation systems are discussed. Finally, current challenges and future perspectives in the context of the NRR are highlighted. This review sheds some light on the development of highly efficient catalytic systems for NH₃ synthesis and stimulates research interests in the unexplored, but promising, research field of the NRR.

Artificial N2 fixation to NH3 by electrocatalytic Ru NPs at low overpotential

Ammonia synthesis, one of the most challenging chemical synthesis processes, plays a vital role in the development of human industry and agriculture. Compared with the industrial Harber-Bosch ammonia process with huge energy input and high CO₂ emissions, the search for a resource-saving, environmentally-friendly ammonia synthesis alternative is extremely urgent. Electrocatalytic nitrogen reduction appears to be a good candidate. In this communication, we report the development of ruthenium nanoparticles as a highly efficient and durable nitrogen reduction reaction (NRR) electrocatalyst in acidic electrolyte under ambient conditions. Such electrochemical NRR catalyst exhibits a large NH₃ formation rate (24.88 μg h^-1 mg^-1 _cat.) with Faradaic efficiency (0.35%) at -0.15 V versus reversible hydrogen electrode, outperforming many reported NRR electrocatalysts. Note that it exhibits high durability and stability during the entire electrochemical NRR process.

Two-dimensional (2D)/2D Interface Engineering of a MoS2/C3N4 Heterostructure for Promoted Electrocatalytic Nitrogen Fixation

The electrochemical nitrogen reduction reaction (NRR) is a very efficient method for sustainable NH₃ production, but it requires effective catalysts to expedite the NRR kinetics and inhibit the concomitant hydrogen evolution reaction (HER). Two-dimensional (2D)/2D interface engineering is an effective method to design powerful catalysts due to intimate face-to-face contact of two 2D materials that facilitates the strong interfacial electronic interactions. Herein, we explored a 2D/2D MoS₂/C₃N₄ heterostructure as an active and stable NRR catalyst. MoS₂/C₃N₄ exhibited a conspicuously improved NRR performance with an NH₃ yield of 18.5 μg h^-1 mg^-1 and a high Faradaic efficiency (FE) of 17.8% at -0.3 V, far better than those of the individual MoS₂ or C₃N₄ component. Density functional theory calculations revealed that the interfacial charge transport from C₃N₄ to MoS₂ could enhance the NRR activity of MoS₂/C₃N₄ by promoting the stabilization of the key intermediate *N₂H on Mo edge sites of MoS₂ and concurrently decreasing the reaction energy barrier. Meanwhile, MoS₂/C₃N₄ rendered a more favorable *H adsorption free energy on S edge sites than on Mo edge sites of MoS₂, thereby protecting the NRR-active Mo edge sites from the competing HER and leading to a high FE.

Atomic Modulation, Structural Design, and Systematic Optimization for Efficient Electrochemical Nitrogen Reduction

Ammonia (NH3) is a pivotal precursor in fertilizer production and a potential energy carrier. Currently, ammonia production worldwide relies on the traditional Haber-Bosch process, which consumes massive energy and has a large carbon footprint. Recently, electrochemical dinitrogen reduction to ammonia under ambient conditions has attracted considerable interest owing to its advantages of flexibility and environmental friendliness. However, the biggest challenge in dinitrogen electroreduction, i.e., the low efficiency and selectivity caused by poor specificity of electrocatalysts/electrolytic systems, still needs to be overcome. Although substantial progress has been made in recent years, acquiring most available electrocatalysts still relies on low efficiency trial-and-error methods. It is thus imperative to establish some critical guiding principles for nitrogen electroreduction toward a rational design and accelerated development of this field. Herein, a basic understanding of dinitrogen electroreduction processes and the inherent relationships between adsorbates and catalysts from fundamental theory are described, followed by an outline of the crucial principles for designing efficient electrocatalysts/electrocatalytic systems derived from a systematic evaluation of the latest significant achievements. Finally, the future research directions and prospects of this field are given, with a special emphasis on the opportunities available by following the guiding principles.

Highly Sensitive and Selective Dopamine Detection Utilizing Nitrogen-Doped Mesoporous Carbon Prepared by a Molten Glucose-Assisted Hard-Template Approach

Nitrogen-doped mesoporous carbons (N-MCs) are promising materials for electrochemical sensors or biosensors. However, facile and effective methods for the preparation of N-MCs for electrochemical detection of dopamine (DA) are required. A molten-glucose-assisted hard-template approach has been developed to synthesize N-MC materials by in situ introduction of nitrogen precursors, including ethylenediaminetetraacetic acid disodium salt (EDTA), dicyandiamide, and melamine. The combined characterization of X-ray diffraction (XRD), N₂ sorption, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) indicate the successful preparation of N-MC materials. Most importantly, after detailed examination by cyclic voltammetry (CV) and differential pulse voltammetry (DPV), N-MC obtained by using melamine as precursor (designated as N-MC-MA) displays good catalytic activity for electrochemical oxidation of DA. The N-MC-MA-based DA sensor shows a linear range from 0.2-8 μm with a detection limit of 0.05 μm in the presence of ascorbic acid (AA) and uric acid (UA), thus showing excellent sensitivity and selectivity for electrochemical DA detection.

Bioinspired Electrocatalyst for Electrochemical Reduction of N2 to NH3 in Ambient Conditions

Industrial ammonia production depends heavily on the traditional Haber-Bosch method at the expense of CO₂ emissions and large energy consumptions. Artificial fixation of nitrogen to ammonia is therefore regarded as a promising path to yield ammonia in energy-saving conditions. However, a competent electrocatalyst is highly desired, owing to the extremely stable bond of N≡N. In this work, we report Fe₂(MoO₄)₃ nanoparticles as a non-noble-metal electrocatalyst, inspired by nitrogenase enzymes for electrochemically converting nitrogen into ammonia, which achieves a Faradic efficiency of 9.1% and an excellent NH₃ yield of 18.16 μg h^-1 mg^-1 cat in 0.1 M sodium sulfate at -0.6 V vs reversible hydrogen electrode. Also, it has a better ammonia yield rate of 20.09 μg h^-1 mg^-1 cat in 0.1 M hydrochloric acid. Moreover, this noble-metal-free catalyst exhibits a unique reaction process selectivity and stability compared with the other catalysts working in harsh conditions. The specific reaction processes are analyzed by density functional theoretical calculations to gain insights into the nitrogen reduction reaction (NRR) by this catalyst.

MoP supported on reduced graphene oxide for high performance electrochemical nitrogen reduction

MoP nanoseeds grown on rGO for high-performance electrocatalytic nitrogen fixation.

Defective S/N co-doped carbon cloth via a one-step process for effective electroreduction of nitrogen to ammonia

The electroreduction of nitrogen (N₂) has gained increasing attention as a promising route to achieve green and sustainable ammonia (NH₃) production.

Bi nanodendrites for efficient electrocatalytic N2 fixation to NH3 under ambient conditions

Bi nanodendrite acts as an efficient electrocatalyst for ambient N₂-to-NH₃ with NH₃ yield rate of 25.86 μg h⁻¹ mg⁻¹_cat. and faradaic efficiency of 10.8% at −0.60 V and −0.55 V versus RHE, respectively.

Ambient electrochemical NH3 synthesis from N2 and water enabled by ZrO2 nanoparticles

ZrO₂ nanoparticles act as an efficient electrocatalyst for ambient N₂-to-NH₃ fixation. In 0.1 M HCl, it attains a large NH₃ yield rate of 24.74 μg h⁻¹ mg_cat.⁻¹ with a faradaic efficiency of 5.0% at −0.45 V vs. RHE.

Plasma-engineered NiO nanosheets with enriched oxygen vacancies for enhanced electrocatalytic nitrogen fixation

Plasma technique can readily create the enriched oxygen vacancies which enable the NiO to be an active and durable catalyst for electrocatalytic fixation of N₂ to NH₃.

Ti3+ self-doped TiO2−x nanowires for efficient electrocatalytic N2 reduction to NH3

Ti³⁺–TiO_2−x/TM behaves as an efficient electrocatalyst for ambient N₂-to-NH₃ fixation with a high faradaic efficiency of 14.62% and a NH₃ yield of 3.51 × 10⁻¹¹ mol s⁻¹ cm⁻² at −0.55 V versus a reversible hydrogen electrode in 0.1 M Na₂SO₄.

P-Doped graphene toward enhanced electrocatalytic N2 reduction

P doping greatly improves electrochemical N₂ reduction over graphene. In 0.5 M LiClO₄, P-doped graphene attains a high Faradic efficiency of 20.82% and a large NH₃ yield of 32.33 μg h⁻¹ mg_cat.⁻¹ at −0.65 V vs. RHE.

Bifunctional PtCu electrocatalysts for the N2 reduction reaction under ambient conditions and methanol oxidation

PtCu nanoalloys were employed as bifunctional electrocatalysts in both the N₂ reduction and methanol oxidation, in which the electrocatalytic activity and stability is composition dependent and highly improved compared to their counterpart.

Boron-doped silver nanosponges with enhanced performance towards electrocatalytic nitrogen reduction to ammonia

In this communication, we develop a simple one-step method to prepare boron doped silver nanosponges (B-Ag NSs) with a boron content of 15 at%. Benefiting from their interconnected porous structures and composition effect, the B-Ag NSs achieve excellent NRR performance and stability. The proposed synthetic strategy provides promising insight into the preparation of boron doped metallic nanomaterials for electrocatalytic fields.