Search Results (70)

With changes in the global energy structure, ammonia has emerged as a favorable hydrogen storage medium due to its excellent properties. This work details the synthesis of a barium-doped cobalt–iron alloy catalyst via subsequent heat treatment. This alloy efficiently catalyzes the decomposition of ammonia into hydrogen. The results showed that using characterization methods such as TEM and XRD indicated that adding Ba to this system could regulate the microstructure of the Co-Fe alloy. After calcination, the barium promoted a reduction in the particle size of Co-Fe nanoparticles, enabling their uniform dispersion on the surface and a more uniform dispersion and improving the accessibility of the exposed surface. The optimized catalyst (0.05Ba-0.25CoFe/CeO₂) achieved an ammonia conversion of 93.2% at 550 °C under a gas hourly space velocity of 30,000 mL·g_cat⁻¹·h⁻¹. Mechanistic analysis based on XPS and CO₂-TPD results indicated that the barium optimized the electronic structure and alkaline sites of Co-Fe, promoted the desorption of nitrogen, and thereby accelerated the reaction kinetics of ammonia decomposition. This research provides a strategic method and theoretical basis for designing high-performance non-precious metal catalysts for ammonia decomposition. Full article

The pursuit of sustainable ammonia production has accelerated the development of electrocatalytic pathways capable of operating under ambient conditions with renewable electricity. Recent studies have revealed that the efficiency and selectivity of both electrochemical nitrogen reduction reaction (eNRR) and nitrate reduction reaction (eNO₃RR) are not governed solely by catalyst composition, but by the synergistic interplay among electrolyte identity, interfacial solvation structure, and catalyst architecture. Hydrated cations such as Li⁺ profoundly reshape the electric double layer, polarize interfacial water, and lower activation barriers for key proton–electron transfer steps, thereby redefining the electrolyte as an active promoter. Parallel advances in structural engineering, including alloying, heteroatom doping, controlled defect formation, and nanoscale morphological control, have enabled the optimization of intermediate adsorption energies while simultaneously suppressing competing hydrogen evolution. In addition, the emergence of metal–organic-framework (MOF)-derived single-atom catalysts has demonstrated that atomically dispersed transition-metal centers anchored within dynamically adaptable matrices can deliver exceptional Faradaic efficiencies, high turnover rates, and long-term operational durability. These developments highlight a unified strategy in which electrolyte–catalyst coupling, rational structural modification, and atomic-scale design principles converge to enable predictable and high-performance ammonia electrosynthesis. This review integrates mechanistic insights across these domains and outlines future directions for translating molecular-level understanding into scalable technologies for green ammonia production. Full article

Nitrate (NO₃⁻), as a stable nitrogen-containing compound, has caused serious harm to the ecological environment and human health. To reduce nitrate pollution, the catalytic reduction of nitrate (NO₃RR) to ammonia (NH₃) is a very promising solution. Recently, single-atom catalysts (SACs) have received extensive attention due to their excellent activity and stability. Here, we study the nitrate catalytic reduction properties of hexagonal-boron-nitride-(h-BN)-supported single-atom Cu systematically and theoretically and compare it with monolayer h-BN. We find that (1) due to the stronger electronegativity of the N atom, Cu atom is preferentially doped at the N top site, resulting in the significant electron rearrangement; (2) the doped Cu atom at the N top site for monolayer h-BN can provide extra 3d-orbital electrons at the Fermi level, which can significantly enhance the conductivity, reduce the bandgap width, and increase the reducibility; (3) the NO₃⁻ ion preferentially adsorbs at the hollow site of monolayer h-BN, while the NO₃⁻ ion is adsorbed more strongly at the Cu top site of h-BN-supported single-atom Cu due to the abundant d-electron supply from the Cu atom; (4) single-atom Cu can significantly reduce the energy barrier of the rate-determining step (RDS) and increase the probability of nitrate reduction. In conclusion, h-BN-supported single-atom Cu exhibits excellent catalytic performance of NO₃RR. Full article

In this study, we experimentally demonstrate that the magnetic properties of nitrogen-doped graphene (NG) are influenced by the configuration of nitrogen dopants, namely graphitic, pyridinic, and pyrrolic, along with the overall nitrogen concentration. The NG materials were prepared via a two-step thermal treatment process. The first step involved heating in ammonia at 400 °C, followed by a second post-annealing step at 600 °C. Scanning Electron Microscopy–Energy Dispersive X-ray Spectroscopy (SEM–EDS) analysis performed at 25 μm resolution confirmed uniform elemental distribution across the samples. X-ray photoelectron spectroscopy (XPS) revealed that while the total nitrogen content decreased from 11.9 at.% in NG to 5.5 at.% in the post-annealed sample, the ratio of graphitic to pyrrolic nitrogen increased from 0.4% to 3.8% and the ratio of graphitic to pyridinic nitrogen increased from 0.8% to 2.5%. Raman spectroscopy confirmed the presence of prominent D and G bands at ~1352 cm⁻¹ and ~1589 cm⁻¹, respectively, along with a 2D band at ~2692 cm⁻¹, indicating the presence of few-layered graphene and defect-related features. The ${\displaystyle \frac{{\mathrm{I}}_{\mathrm{D}}}{{\mathrm{I}}_{\mathrm{G}}}}$ ratio increased from 1.12 to 1.27 in the post-annealed sample, indicating increased disorder after annealing. Magnetic characterization showed a marked enhancement in the magnetic properties with increased graphitic nitrogen content. The saturation magnetization (M_s) reached 0.13 emu g⁻¹, ~42% higher than that of the material heated in ammonia, with the coercivity increasing from 40 Oe to 750 Oe. These results emphasize the pivotal role of nitrogen configuration in the graphene host, specifically the promotion of graphitic nitrogen species, in tailoring the ferromagnetic response of NG. Full article

This research seeks to investigate extremely efficient catalysts for the nitrogen reduction process (NRR), utilizing machine learning (ML)-aided density functional theory (DFT) computations. Specifically, we investigate dual transition metal atoms anchored on hexagonal nitrogen-doped graphene (TM₁-TM₂@N₆G) as prospective high-activity catalysts for the NRR. The findings indicate that the synergistic effect of dual transition metal atoms in the TM₁-TM₂@N₆G catalyst overcomes the intrinsic constraints of the linear relationship among intermediates, facilitating the activation and adsorption of N₂, thereby exhibiting significant potential for ammonia synthesis through N₂ reduction. Particularly, four catalysts screened by ML and DFT exhibit good stability and excellent selectivity and activation towards N₂. Among them, the catalysts Ti-Cr@N₆G, Ti-Mo@N₆G, and Ti-Pd@N₆G possess two reaction pathways with minimum reaction energies of 0.55 eV, 0.50 eV, and 0.40 eV, respectively. Remarkably, Ti-Co@N₆G, which features a single reaction pathway, exhibits a reaction energy lower than 0.05 eV, allowing the NRR to proceed spontaneously. It is noteworthy that incorporating ML into DFT calculations facilitates the rapid screening of all transition metal combinations, significantly accelerating the research on catalytic performance and optimizing the selection of catalysts. Full article

The widespread contamination of aquatic systems by ciprofloxacin (CIP)—a persistent fluoroquinolone antibiotic—poses severe ecological risks due to its antibacterial resistance induction. Conventional sulfate radical-based advanced oxidation processes (SR-AOPs) suffer from inefficient catalyst synthesis, exemplified by low-yield ZIF-67 precursors (typically <25%). To address this, a nitrogen-doped carbon composite Co₃O₄/N@C was synthesized via ammonia-assisted ligand exchange followed by pyrolysis, using N-doped ZIF-67 as a self-sacrificial template. The ammonia incorporation quadrupled precursor yield compared to ammonia-free methods. This catalyst activated peroxydisulfate (PDS) to degrade 95% CIP within 90 min under the optimized conditions (0.5 g/L catalyst, 2 mmol/L PDS, pH 5), representing a 30% enhancement over non-ammonia analogs. Mechanistic studies identified singlet oxygen (¹O₂) as the dominant reactive species, facilitated by N-doped carbon-mediated electron transfer. This strategy overcomes the scalability barrier of MOF-derived catalysts for practical antibiotic wastewater remediation. Full article

A novel approach was developed in this work in which composite nanofiltration (NF) membranes were directly and efficiently fabricated with control of the membrane pore structure and surface morphology. The fabrication of mesoporous silicon-modified polysulfone blend membranes is achieved via a phase inversion method. The structural morphology, surface functional group analysis, elemental analysis, hydrophilicity, chargeability, and nitrogen pollutant (ammonia nitrogen, nitrate nitrogen, total nitrogen) rejection properties of the modified membranes were found to be dependent on the amount of mesoporous silicon incorporated. The combination of the mesoporous silicon framework layer can not only effectively improve the surface structure of the modified membrane with a narrow pore size distribution but also increase the rejection of nitrogen pollutants compared with pure NF membranes. The mesoporous material interlayer can absorb and store the aqueous amino solution to facilitate the subsequent interfacial polymerization as well as induce changes in the pore radius and surface structure. Compared with pure NF composite membranes, the modified blend membranes exhibit increased water permeation flux as high as 29.09 L m⁻² h⁻¹ at 0.2 MPa. The results show that the optimum doping amount of mesoporous silicon is in the range of 0.5–1.0%. Characterization studies demonstrated that the addition of mesoporous silicon leads to a decreased membrane pore size. Then the retention of nitrogen pollutants was enhanced because of a combination of hydrophilicity enhancement from the carboxylic and hydroxyl functional groups present in their surfaces leading to electrostatic repulsion between functional groups present in the membranes and the nitrogen pollutant molecules. Full article

Electrocatalytic nitrate reduction to ammonia (NO₃RR) is a promising approach to recycle nitrogen from nitrate pollutants, yet it remains challenged by low Faradaic efficiency and insufficient NH₃ production. Herein, Cu-doped nanoporous Co₂P (np-Co_2−xCu_xP) is reported as electrocatalyst for NO₃RR, achieving an ammonia yield rate of 30.6 mg h⁻¹ cm⁻² with a Faradaic efficiency of 93.4% at −0.3 V vs. RHE. In-situ spectroscopic analyses indicate that Cu incorporation modifies the surface electronic structure, resulting in the promotion of *H adsorption and *NO₂⁻ hydrogenation, thereby facilitating efficient ammonia generation. Full article

Nitrogen-doped graphene quantum dots (NGQDs) are made by heating a mixture of GQDs and ammonia using a thermochemical method. The optical properties of the samples were studied. Here, the role of the temperature used in the annealing process is investigated. It is found that with the increase in heating temperature, the sp² fraction content continuously increases, and the photoluminescence (PL) blue shift continuously increases. The 550 nm peak of GQDs shifts from 550 nm to 513 nm NGQDs synthesized at 300 °C. The normalized PL intensity shows a significant blue shift in the emission peak of the NGQD samples compared to the GQDs. The peak position of the GQDs is 555 nm, while the peak positions of the NGQDs are 511 nm for NGQDs-250, 488 nm for NGQDs-300, and 480 nm for NGQDs-350. Using a simple thermochemical method, we can effectively dope N into GQDs, and it is evident from the electron energy loss spectra that N doping induces the emergence of a new energy level in the electronic structure, which alters the optical properties of NGQDs. Full article

Sintering flue gas contains significant amounts of harmful gases, such as carbon monoxide and nitrogen oxides (NO_x), which pose severe threats to the ecological environment and human health. Selective catalytic reduction (SCR) technology is widely employed for the removal of nitrogen oxides, with copper-cerium-based bimetallic catalysts and their derivatives demonstrating excellent catalytic efficiency in SCR reactions, primarily due to the significant synergistic effect between copper and cerium. This paper summarizes the main factors affecting the catalytic performance of Cu-Ce-based bimetallic catalysts and their derivatives in the selective catalytic reduction of ammonia and carbon monoxide. Key considerations include various preparation methods, doping of active components, and the effects of loading catalysts on different supports. This paper also analyzes the influence of surface oxygen vacancies, redox capacity, acidity, and specific surface area on catalytic performance. Additionally, the anti-poisoning performance and reaction mechanisms of the catalysts are discussed. Finally, the paper proposes strategies for designing high-activity and high-stability catalysts, considering the development prospects and challenges of Cu-Ce-based bimetallic catalysts and their derivatives, with the aim of providing theoretical guidance for optimizing Cu-Ce-based catalysts and promoting their industrial applications. Full article

In this experiment, C₃N₅ was synthesized by pyrolysis of 3-amino-1,2,4 triazole material, and then 1% Co-C₃N₅, 3% Co-C₃N₅, 5% Co-C₃N₅, 7% Co-C₃N₅, and 9% Co-C₃N₅ were synthesized by varying the mass ratio of cobalt chloride to C₃N₅ by stirring and ultrasonic shaking. SEM, XPS, and XRD tests were performed on the synthesized materials. The experimental results showed that Co atoms were successfully doped into C₃N₅. The electrocatalytic reduction experiments were performed to evaluate their NH₃ yields and electrochemical properties. The results showed that the ammonia yield obtained by the electrolysis of the 9% Co-C₃N₅ catalyst as the working electrode in a mixed electrolytic solution of 0.1 mol/L KNO₃ and 0.1 mol/L KOH for 1 h at a potential of −1.0 V vs. RHE was 0.633 ± 0.02 mmol∙h⁻¹∙mg_cat⁻¹, and the Faraday efficiency was 65.98 ± 2.14%; under the same experimental conditions, the ammonia production rate and Faraday efficiency of the C₃N₅ catalyst were 0.049 mmol∙h⁻¹∙mg_cat⁻¹ and 16.41%, respectively, and the ammonia production rate of the C₃N₅ catalyst was nearly 13-fold worse than the 9% Co-C₃N₅, which suggests that Co can improve the Faraday efficiency and ammonia yield of the electrocatalytic reduction of NO₃⁻. This is due to the strong synergistic effect between the cobalt and C₃N₅ components, with C₃N₅ providing abundant and homogeneous sites for nitrogen coordination and the Co-N species present in the material being highly efficient active sites. The slight change in current density after five trials of 9% Co-C₃N₅ and the decrease in ammonia yield by about 12% in five repetitions of the experiment indicate that 9% Co-C₃N₅ can be recycled and work stably in electrocatalytic reactions and has good application prospects. Full article

Graphene and MXenes have emerged as promising materials for gas sensing applications due to their unique properties and superior performance. This review focuses on the fabrication techniques, applications, and sensing mechanisms of graphene and MXene-based composites in gas sensing. Gas sensors are crucial in various fields, including healthcare, environmental monitoring, and industrial safety, for detecting and monitoring gases such as hydrogen sulfide (H₂S), nitrogen dioxide (NO₂), and ammonia (NH₃). Conventional metal oxides like tin oxide (SnO₂) and zinc oxide (ZnO) have been widely used, but graphene and MXenes offer enhanced sensitivity, selectivity, and response times. Graphene-based sensors can detect low concentrations of gases like H₂S and NH₃, while functionalization can improve their gas-specific selectivity. MXenes, a new class of two-dimensional materials, exhibit high electrical conductivity and tunable surface chemistry, making them suitable for selective and sensitive detection of various gases, including VOCs and humidity. Other materials, such as metal-organic frameworks (MOFs) and conducting polymers, have also shown potential in gas sensing applications, which may be doped into graphene and MXene layers to improve the sensitivity of the sensors. Full article

Nickel hydroxide is a potentially cheap non-precious metal catalytic material for alkaline hydrogen evolution reactions (HERs). Herein, a nickel form (NF)-based nitrogen-modified nickel hydroxide (N-Ni(OH)₂/NF) with interlaced two-dimensional (2D) nanosheet structures was synthesized by a simple one-step ammonia vapor-phase hydrothermal method for efficient electrocatalytic HERs. The effect of the reaction temperature of the catalyst preparation on the HERs’ performance was studied in detail. The HER activity of N-Ni(OH)₂/NF is enhanced by the large specific surface area, mass transfer and electron conductivity provided by a unique and suitable 2D nanostructure and nitrogen doping. The obtained N-Ni(OH)₂/NF not only shows a superior HERs performance, but also exhibits good stability during long-term electrolysis. Full article

The reduction of nitrogen oxides (NO_x), critical pollutants from stationary to mobile sources, mainly relies on the selective catalytic reduction (NH₃-SCR) method, employing ammonia to reduce NO_x into nitrogen and water. However, conventional catalysts, while effective, pose both environmental and operational challenges. This study investigates ceria-zirconia-supported molybdenum-based catalysts, exploring the effects of zirconium doping and different catalyst synthesis techniques, i.e., co-precipitation and impregnation. The catalytic performance of the differently prepared samples was significantly influenced by the molybdenum incorporation method and the zirconium content within the ceria-zirconia support. Co-precipitation at higher temperatures resulted in catalysts with better structural attributes but slightly lower catalytic activity compared to those prepared via impregnation. Optimal NO_x reduction (close to 100%) was observed at a 15 mol% zirconium doping level when using the impregnation method. Full article

The electrocatalytic production of ammonia has garnered considerable interest as a potentially sustainable technology for ammonia synthesis. Recently, non-metallic-doped materials have emerged as promising electrochemical catalysts for this purpose. This paper presents a comprehensive review of the latest research on non-metallic-doped materials for electrocatalytic ammonia production. Researchers have engineered a variety of materials, doped with non-metals such as nitrogen (N), boron (B), phosphorus (P), and sulfur (S), into different forms and structures to enhance their electrocatalytic activity and selectivity. A comparison among different non-metallic dopants reveals their distinct effects on the electrocatalytic performance for ammonia production. For instance, N-doping has shown enhanced activity owing to the introduction of nitrogen vacancies (NVs) and improved charge transfer kinetics. B-doping has demonstrated improved selectivity and stability, which is attributed to the formation of active sites and the suppression of competing reactions. P-doping has exhibited increased ammonia generation rates and Faradaic efficiencies, likely due to the modification of the electronic structure and surface properties. S-doping has shown potential for enhancing electrocatalytic performance, although further investigations are needed to elucidate the underlying mechanisms. These comparisons provide valuable insights for researchers to conduct in-depth studies focusing on specific non-metallic dopants, exploring their unique properties, and optimizing their performance for electrocatalytic ammonia production. However, we consider it a priority to provide insight into the recent progress made in non-metal-doped materials and their potential for enabling long-term and efficient electrochemical ammonia production. Additionally, this paper discusses the synthetic procedures used to produce non-metal-doped materials and highlights the advantages and disadvantages of each method. It also provides an in-depth analysis of the electrochemical performance of these materials, including their Faradaic efficiencies, ammonia yield rate, and selectivity. It examines the challenges and prospects of developing non-metallic-doped materials for electrocatalytic ammonia production and suggests future research directions. Full article