NbC Nanoparticles Decorated Carbon Nanofibers as Highly Active and Robust Heterostructural Electrocatalysts for Ammonia Synthesis.

Transition-metal carbides with metallic properties have been extensively used as electrocatalysts due to their excellent conductivity and unique electronic structures. Herein, NbC nanoparticles decorated carbon nanofibers (NbC@CNFs) are proposed as an efficient and robust catalyst for electrochemical synthesis of ammonia from nitrate/nitrite reduction, which achieves a high Faradaic efficiency (FE) of 94.4 % and a large ammonia yield of 30.9 mg h-1 mg-1 cat.. In situ electrochemical tests reveal the nitrite reduction at the catalyst surface follows the *NO pathway and theoretical calculations reveal the formation of NbC@CNFs heterostructure significantly broadens density of states nearby the Fermi energy. Finite element simulations unveil that the current and electric field converge on the NbC nanoparticles along the fiber, suggesting the dispersed carbides are highly active for nitrite reduction.

Crystalline modulation of zirconia for efficient nitrate reduction to ammonia under ambient conditions.

Zirconia as a polycrystalline catalyst can be effectively tuned by doping low-valence elements and meanwhile form abundant oxygen vacancies. Herein, the crystalline structures of zirconia are modulated by scandium doping and proposed as a robust catalyst for nitrate reduction to ammonia. The tetragonal zirconia achieves a maximum ammonia yield of 16.03 mg h-1 mgcat.-1, superior to the other crystal forms. DEMS tests unveil the reaction pathway and theoretical calculations reveal the low free energy of -0.22 eV for nitrate adsorption at the tetragonal zirconia.

Efficient Electrochemical Co-Reduction of Carbon Dioxide and Nitrate to Urea with High Faradaic Efficiency on Cobalt-Based Dual-Sites.

Renewable electricity-powered nitrate/carbon dioxide co-reduction reaction toward urea production paves an attractive alternative to industrial urea processes and offers a clean on-site approach to closing the global nitrogen cycle. However, its large-scale implantation is severely impeded by challenging C-N coupling and requires electrocatalysts with high activity/selectivity. Here, cobalt-nanoparticles anchored on carbon nanosheet (Co NPs@C) are proposed as a catalyst electrode to boost yield and Faradaic efficiency (FE) toward urea electrosynthesis with enhanced C-N coupling. Such Co NPs@C renders superb urea-producing activity with a high FE reaching 54.3% and a urea yield of 2217.5 µg h-1 mgcat. -1, much superior to the Co NPs and C nanosheet counterparts, and meanwhile shows strong stability. The Co NPs@C affords rich catalytically active sites, fast reactant diffusion, and sufficient catalytic surfaces-electrolyte contacts with favored charge and ion transfer efficiencies. The theoretical calculations reveal that the high-rate formation of *CO and *NH2 intermediates is crucial for facilitating urea synthesis.

A Metal Coordination Number Determined Catalytic Performance in Manganese Borides for Ambient Electrolysis of Nitrogen to Ammonia.

A new strategy that can effectively increase the nitrogen reduction reaction performance of catalysts is proposed and verified by tuning the coordination number of metal atoms. It is found that the intrinsic activity of Mn atoms in the manganese borides (MnBx) increases in tandem with their coordination number with B atoms. Electron-deficient boron atoms are capable of accepting electrons from Mn atoms, which enhances the adsorption of N2 on the Mn catalytic sites (*) and the hydrogenation of N2 to form *NNH intermediates. Furthermore, the increase in coordination number reduces the charge density of Mn atoms at the Fermi level, which facilitates the desorption of ammonia from the catalyst surface. Notably, the MnB4 compound with a Mn coordination number of up to 12 exhibits a high ammonia yield rate (74.9 ± 2.1 µg h-1 mgcat -1) and Faradaic efficiency (38.5 ± 2.7%) at -0.3 V versus reversible hydrogen electrode (RHE) in a 0.1 m Li2SO4 electrolyte, exceeding those reported for other boron-related catalysts.

Mitigation of electromagnetic pulses interfering with Thomson parabola ion spectrometers at XG-III laser facility.

The Thomson parabola ion spectrometer is vulnerable to intense electromagnetic pulses (EMPs) generated by a high-power laser interacting with solid targets. A metal shielding cage with a circular aperture of 1 mm diameter is designed to mitigate EMPs induced by a picosecond laser irradiating a copper target in an experiment where additionally an 8-ns delayed nanosecond laser is incident into an aluminum target at the XG-III laser facility. The implementation of the shielding cage reduces the maximum EMP amplitude inside the cage to 5.2 kV/m, and the simulation results indicate that the cage effectively shields electromagnetic waves. However, the laser-accelerated relativistic electrons which escaped the target potential accumulate charge on the surface of the cage, which is responsible for the detected EMPs within the cage. To further alleviate EMPs, a lead wall and an absorbing material (ECCOSORB AN-94) were added before the cage, significantly blocking the propagation of electrons. These findings provide valuable insights into EMP generation in large-scale laser infrastructures and serve as a foundation for electromagnetic shielding design.

Fabrication of a hierarchical NiTe@NiFe-LDH core-shell array for high-efficiency alkaline seawater oxidation.

Herein, a hierarchical NiTe@NiFe-LDH core-shell array on Ni foam (NiTe@NiFe-LDH/NF) demonstrates its effectiveness for oxygen evolution reaction (OER) in alkaline seawater electrolyte. This NiTe@NiFe-LDH/NF array showcases remarkably low overpotentials of 277 mV and 359 mV for achieving current densities of 100 and 500 mA cm-2, respectively. Also, it shows a low Tafel slope of 68.66 mV dec-1. Notably, the electrocatalyst maintains robust stability over continuous electrolysis for at least 50 h at 100 mA cm-2. The remarkable performance and hierarchical structure advantages of NiTe@NiFe-LDH/NF offer innovative insights for designing efficient seawater oxidation electrocatalysts.

Unveiling Cutting-Edge Developments in Electrocatalytic Nitrate-to-Ammonia Conversion.

The excessive enrichment of nitrate in the environment can be converted into ammonia (NH3) through electrochemical processes, offering significant implications for modern agriculture and the potential to reduce the burden of the Haber-Bosch (HB) process while achieving environmentally friendly NH3 production. Emerging research on electrocatalytic nitrate reduction (eNitRR) to NH3 has gained considerable momentum in recent years for efficient NH3 synthesis. However, existing reviews on nitrate reduction have primarily focused on limited aspects, often lacking a comprehensive summary of catalysts, reaction systems, reaction mechanisms, and detection methods employed in nitrate reduction. This review aims to provide a timely and comprehensive analysis of the eNitRR field by integrating existing research progress and identifying current challenges. This review offers a comprehensive overview of the research progress achieved using various materials in electrochemical nitrate reduction, elucidates the underlying theoretical mechanism behind eNitRR, and discusses effective strategies based on numerous case studies to enhance the electrochemical reduction from NO3 - to NH3. Finally, this review discusses challenges and development prospects in the eNitRR field with an aim to guide design and development of large-scale sustainable nitrate reduction electrocatalysts.

Hierarchical Architecture Engineering of Branch-Leaf-Shaped Cobalt Phosphosulfide Quantum Dots: Enabling Multi-Dimensional Ion-Transport Channels for High-Efficiency Sodium Storage.

New-fashioned electrode hosts for sodium-ion batteries (SIBs) are elaborately engineered to involve multifunctional active components that can synergistically conquer the critical issues of severe volume deformation and sluggish reaction kinetics of electrodes toward immensely enhanced battery performance. Herein, it is first reported that single-phase CoPS, a new metal phosphosulfide for SIBs, in the form of quantum dots, is successfully introduced into a leaf-shaped conductive carbon nanosheet, which can be further in situ anchored on a 3D interconnected branch-like N-doped carbon nanofiber (N-CNF) to construct a hierarchical branch-leaf-shaped CoPS@C@N-CNF architecture. Both double carbon decorations and ultrafine crystal of the CoPS in-this exquisite architecture hold many significant superiorities, such as favorable train-relaxation, fast interfacial ion-migration, multi-directional migration pathways, and sufficiently exposed Na+ -storage sites. In consequence, the CoPS@C@N-CNF affords remarkable long-cycle durability over 10 000 cycles at 20.0 A g-1 and superior rate capability. Meanwhile, the CoPS@C@N-CNF-based sodium-ion full cell renders the potential proof-of-feasibility for practical applications in consideration of its high durability over a long-term cyclic lifespan with remarkable reversible capacity. Moreover, the phase transformation mechanism of the CoPS@C@N-CNF and fundamental springhead of the enhanced performance are disclosed by in situ X-ray diffraction, ex situ high-resolution TEM, and theoretical calculations.

Co3O4 nanoparticles embedded in porous carbon nanofibers enable efficient nitrate reduction to ammonia.

The nitrate reduction reaction is emerging as having tremendous potential to mitigate nitrate pollution and simultaneously produce valuable ammonia. Here, we propose Co3O4 nanoparticles embedded in porous carbon nanofibers (Co3O4@CNF) as a high-efficiency catalyst to convert nitrate to ammonia, and it achieves a high faradaic efficiency of 92.7% and an extremely large NH3 yield of 23.4 mg h-1 mg-1cat, and also presents excellent electrochemical stability. Theoretical calculations reveal that the potential determining step (PDS) reaches as low as 0.28 eV. This work is expected to open a new avenue to rationally design robust noble-metal-free catalysts for the electrochemical synthesis of ammonia.

Cr3C2 nanoparticles decorated carbon nanofibers for efficient nitrate reduction to ammonia at ambient conditions.

Electrochemical nitrate (NO3-) reduction is a promising approach to relieve nitrate pollution and produce value-added ammonia (NH3), but efficient and durable catalysts are required due to the large bond dissociation energy of nitrate and low selectivity. Herein, we propose chromium carbide (Cr3C2) nanoparticles loaded carbon nanofibers (Cr3C2@CNFs) as electrocatalysts to convert nitrate to ammonia. In phosphate buffer saline containing 0.1 mol L-1 NaNO3, such catalyst achieves a large NH3 yield of 25.64 mg h-1 mg-1cat. and a high faradaic efficiency of 90.08% at -1.1 V vs the reversible hydrogen electrode, which also shows excellent electrochemical durability and structural stability. Theoretical calculations reveal the adsorption energy for nitrate at Cr3C2 surfaces reaches -1.92 eV and the potential determining step (*NO→*N) for Cr3C2 hits a low energy increase of 0.38 eV.

Rational Construction of Heterostructured Cu3 P@TiO2 Nanoarray for High-Efficiency Electrochemical Nitrite Reduction to Ammonia.

Electroreduction of nitrite (NO2 - ) to valuable ammonia (NH3 ) offers a sustainable and green approach for NH3 synthesis. Here, a Cu3 P@TiO2 heterostructure is rationally constructed as an active catalyst for selective NO2 - -to-NH3 electroreduction, with rich nanosized Cu3 P anchored on a TiO2 nanoribbon array on Ti plate (Cu3 P@TiO2 /TP). When performed in the 0.1 m NaOH with 0.1 m NaNO2 , the Cu3 P@TiO2 /TP electrode obtains a large NH3 yield of 1583.4 µmol h-1  cm-2 and a high Faradaic efficiency of 97.1%. More importantly, Cu3 P@TiO2 /TP also delivers remarkable long-term stability for 50 h electrolysis. Theoretical calculations indicate that intermediate adsorption/conversion processes on Cu3 P@TiO2 interfaces are synergistically optimized, substantially facilitating the conversion of NO2 - -to-NH3 .

Efficient electrocatalytic reduction of nitrate to ammonia over fibrous SmCoO3 under ambient conditions.

We report SmCoO3 nanofibers as an efficient catalyst for nitrate reduction to ammonia. This catalyst achieves a large NH3 yield of 14.4 mg h-1 mgcat.-1 and a high faradaic efficiency of 81.3% at -1.0 V vs. RHE in 0.1 M PBS with 0.1 M NaNO3, and it also displays excellent electrochemical durability and structural stability. Theoretical calculations indicate that Sm-O and Co-O bonds have an incredibly low adsorption energy of -0.1 eV, which can significantly reduce the applied potential and hence enhance the catalytic activity.

Durable Electrocatalytic Reduction of Nitrate to Ammonia over Defective Pseudobrookite Fe2 TiO5 Nanofibers with Abundant Oxygen Vacancies.

We propose the pseudobrookite Fe2 TiO5 nanofiber with abundant oxygen vacancies as a new electrocatalyst to ambiently reduce nitrate to ammonia. Such catalyst achieves a large NH3 yield of 0.73 mmol h-1 mg-1 cat. and a high Faradaic Efficiency (FE) of 87.6 % in phosphate buffer saline solution with 0.1 M NaNO3 , which is lifted to 1.36 mmol h-1 mg-1 cat. and 96.06 % at -0.9 V vs. RHE for nitrite conversion to ammonia in 0.1 M NaNO2 . It also shows excellent electrochemical durability and structural stability. Theoretical calculation reveals the enhanced conductivity of this catalyst and an extremely low free energy of -0.28 eV for nitrate adsorption at the presence of vacant oxygen.

Unveiling selective nitrate reduction to ammonia with Co3O4 nanosheets/TiO2 nanobelt heterostructure catalyst.

Electrochemical nitrate (NO3-) reduction reaction (NO3RR) possesses two-pronged properties for sustainable ammonia (NH3) synthesis and mitigating NO3- contamination in water. However, the sluggish kinetics for the direct eight-electron NO3--to-NH3 conversion makes a formidable challenge to develop efficient electrocatalysts. Herein, we report a heterostructure of Co3O4 nanosheets decorated TiO2 nanobelt array on titanium plate (Co3O4@TiO2/TP) as an efficient NO3RR electrocatalyst. Both experimental and density theory calculations reveal that the heterostructure of Co3O4@TiO2 establishes a built-in electric field which can optimize the electron migration kinetics, as well as facilitate the adsorption and fixation of NO3- on the electrode surface, ensuring the selectivity to NH3. As expected, the designed Co3O4@TiO2/TP exhibits a remarkable Faradaic efficiency of 93.1 % and a remarkable NH3 yield as high as 875 µmol h-1 cm-2, superior to Co3O4/TP and TiO2/TP. Significantly, it also demonstrates strong electrochemical durability.

Boosting electrochemical nitrate-to-ammonia conversion by self-supported MnCo2O4 nanowire array.

Direct electrocatalytic reduction of nitrate (NO3-) is an efficient route to simultaneously synthesize ammonia (NH3) and remove NO3- pollutants under ambient conditions, however, it is hindered by the lack of efficient and stable catalysts. Herein, a self-supported spinel-type MnCo2O4 nanowire array is demonstrated for exclusively catalyzing the conversion of NO3- to NH3, achieving a high Faradic efficiency of 97.1% and a large NH3 yield of 0.67 mmol h-1 cm-2. Furthermore, density functional analysis reveals that MnCo2O4 (220) surface has high activity for NO3- reduction with a low energy barrier of 0.46 eV for *NO to *NOH.

Co/N-doped carbon nanospheres derived from an adenine-based metal organic framework enabled high-efficiency electrocatalytic nitrate reduction to ammonia.

Electrocatalytic nitrate (NO3-) reduction provides us a dual-function strategy for N-contaminant removal and value-added ammonia (NH3) synthesis. However, there is still a lack of efficient electrocatalysts for selective NO3- reduction. Herein, we report the development of Co/N-doped carbon nanospheres derived from an adenine-based metal organic framework (Co@NC) as an attractive electrocatalyst for efficient NH3 synthesis through the reduction of NO3-. Such Co@NC manifests a notable faradaic efficiency of 96.5% and a high NH3 yield of up to 758.0 µmol h-1 mgcat.-1 in 0.1 M NO3--containing 0.1 M NaOH. Moreover, it also demonstrates strong electrochemical stability.

Heterogenous Cu@ZrO2 nanofibers enable efficient electrocatalytic nitrate reduction to ammonia under ambient conditions.

In this study, we construct a Cu@ZrO2 heterogenous structure as a new catalyst that achieves a large NH3 yield of 15.4 mg h-1 mg-1cat. and a high faradaic efficiency of 67.6% at -0.7 V vs. RHE in 0.1 M PBS with 0.1 M NaNO3, and it also shows excellent electrochemical durability and structural stability. Theoretical calculations reveal an extremely low adsorption energy of -1.54 eV at Cu surfaces and Cu can significantly reduce the applied overpotential and correspondingly promote the catalytic activity.

Enhancing Electrocatalytic NO Reduction to NH3 by the CoS Nanosheet with Sulfur Vacancies.

Electrochemical reduction of NO to NH3 is of great significance for mitigating the accumulation of nitrogen oxides and producing valuable NH3. Here, we demonstrate that the CoS nanosheet with sulfur vacancies (CoS1-x) behaves as an efficient catalyst toward electrochemical NO-to-NH3 conversion. In 0.2 M Na2SO4 electrolyte, such CoS1-x displays a large NH3 yield rate (44.67 µmol cm-2 h-1) and a high Faradaic efficiency (53.62%) at -0.4 V versus the reversible hydrogen electrode, outperforming the CoS counterpart (27.02 µmol cm-2 h-1; 36.68%). Moreover, the Zn-NO battery with CoS1-x shows excellent performance with a power density of 2.06 mW cm-2 and a large NH3 yield rate of 1492.41 µg h-1 mgcat.-1. Density functional theory was performed to obtain mechanistic insights into the NO reduction over CoS1-x.

CoO nanoparticle decorated N-doped carbon nanotubes: a high-efficiency catalyst for nitrate reduction to ammonia.

Ambient electrochemical NO3- reduction is emerging as an appealing approach toward eliminating NO3- contaminants and generating NH3 simultaneously, but its efficiency is challenged by a lack of active and selective electrocatalysts. In this work, we report CoO nanoparticle decorated N-doped carbon nanotubes as an efficient catalyst for highly selective hydrogenation of NO3- to NH3. In 0.1 M NaOH electrolyte with 0.1 M NO3-, this catalyst is capable of achieving a large NH3 yield of up to 9041.6 ± 370.7 µg h-1 cm-2 and a high faradaic efficiency of 93.8 ± 1.5%, with excellent durability. Theoretical calculations reveal the catalytic mechanisms.

High-Performance Electrochemical Nitrate Reduction to Ammonia under Ambient Conditions Using a FeOOH Nanorod Catalyst.

Electrocatalytic nitrate reduction is promising as an environmentally friendly process to produce high value-added ammonia with simultaneous removal of nitrate, a widespread nitrogen pollutant, for water treatment; however, efficient electrocatalysts with high selectivity are required for ammonia formation. In this work, FeOOH nanorod with intrinsic oxygen vacancy supported on carbon paper (FeOOH/CP) is proposed as a high-performance electrocatalyst for converting nitrate to ammonia at room temperature. When operated in a 0.1 M phosphate-buffered saline (PBS) solution with 0.1 M NaNO3, FeOOH/CP is able to obtain a large NH3 yield of 2419 µg h-1 cm-2 and a surprisingly high Faradic efficiency of 92% with excellent stability. Density functional theory calculation demonstrates that the potential-determining step for nitrate reduction over FeOOH (200) is *NO2H + H+ + e- → *NO + H2O.