Fe Foam-Supported FeS2-MoS2 Electrocatalyst for N2 Reduction under Ambient Conditions

Tunable N2 Fixation Enabled by Ferroelectric Switching in Doped Graphene/In2Se3 Dual-Atom Catalysts

The electrochemical nitrogen reduction reaction (NRR) provides a sustainable alternative to ammonia synthesis. However, the development of catalysts with high activity and selectivity under ambient conditions remains a significant challenge. In this work, we propose a class of dual-atom catalysts (DACs), consisting of two metal atoms embedded in nitrogen-doped porous graphene (M2NPG) supported on a ferroelectric α-In2Se3 monolayer. Using density functional theory (DFT) calculations, we explore the effect of ferroelectric polarization switching on the structural stability, catalytic performance, and reaction mechanisms of these DACs. By computationally screening 27 metal atoms as active sites, we identify four promising candidates (V, Co, Ru, and Ta) with V2NPG@In2Se3 standing out due to its exceptional properties. The precise control of NRR pathways, along with tunable limiting potentials and selective product formation, can be achieved through the polarization switching of the α-In2Se3 monolayer. The combination of low limiting potential, abundant active sites, tunable catalytic behavior, and high selectivity against the hydrogen evolution reaction (HER) highlights the potential of V2NPG@In2Se3 as a promising alternative to traditional single-atom catalysts. This work demonstrates a versatile strategy for integrating DACs with ferroelectric materials, offering valuable insights into designing next-generation catalysts for NRR and beyond.

Synthesis and Electrocatalytic Applications of Layer-Structured Metal Chalcogenides Composites

Featured with the attractive properties such as large surface area, unique atomic layer thickness, excellent electronic conductivity, and superior catalytic activity, layered metal chalcogenides (LMCs) have received considerable research attention in electrocatalytic applications. In this review, the approaches developed to synthesize LMCs-based electrocatalysts are summarized. Recent progress in LMCs-based composites for electrochemical energy conversion applications including oxygen reduction reaction, carbon dioxide reduction reaction, oxygen evolution reaction, hydrogen evolution reaction, overall water splitting, and nitrogen reduction reaction is reviewed, and the potential opportunities and practical obstacles for the development of LMCs-based composites as high-performing active substances for electrocatalytic applications are also discussed. This review may provide an inspiring guidance for developing high-performance LMCs for electrochemical energy conversion applications.

Enhancing Nitrogen Reduction Reaction through Formation of 2D/2D Hybrid Heterostructures of MoS2@rGO

Given the challenging task of constructing an efficient nitrogen reduction reaction (NRR) electrocatalyst with enhanced ambient condition performance, properties such as high specific surface area, fast electron transfer, and design of the catalyst surface constitute a group of key factors to be taken into consideration to guarantee outstanding catalytic performance and durability. Thereof, this work investigates the contribution of the 2D/2D heterojunction interface between MoS2 and reduced graphene oxide (rGO) on the electrocatalytic synthesis of NH3 in an alkaline media. The results revealed remarkable NRR performance on the MoS2@rGO 2D/2D hybrid electrocatalyst, characterized by a high NRR sensitivity (faradaic efficiency) of 34.7% with an NH3 yield rate of 3.98 ± 0.19 mg h-1 cm-2 at an overpotential of -0.3 V vs RHE in 0.1 M KOH solution. The hybrid electrocatalysts also exhibited selectivity for NH3 synthesis against the production of the hydrazine (N2H4) byproduct, hindrance of the competitive hydrogen evolution reaction (HER), and good durability over an operation period of 8 h. In hindsight, the study presented a low-cost and highly efficient catalyst design for achieving enhanced ammonia synthesis in alkaline media via the formation of defect-rich ultrathin MoS2@rGO nanostructures, consisting predominantly of an HER-hindering hexagonal 2H-MoS2 phase.

Tuning the interface of MIMII(OH)F@MIMII1-xS (MⅠ: Ni, Co; MⅡ: Co, Fe) by atomic replacement strategy toward high performance overall water splitting

Constructing heterostructure is considered as one of the most promising strategies to reveal high efficiency hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) performance. Nevertheless, it is highly challenging to obtain stable interfaces and sufficient active sites via conventional method. In addition, Ni, Co and Fe elements share the valence electron structures of 3d6-84s2, the appropriate integration of these metals to induce synergistic effect in multicomponent electrocatalysts can enhance electrochemical activity. Herein, in this work, the MIMII(OH)F@MIMII1-xS (NiFe(OH)F@NiFe1-xS, NiCo(OH)F@NiCo1-xS, CoFe(OH)F@CoFe1-xS) autogenous heterostructure on nickel foam are constructed. As a result, NiFe(OH)F@NiFe1-xS-0.05, NiCo(OH)F@NiCo1-xS-0.05, and CoFe(OH)F@CoFe1-xS-0.05 demonstrate outstanding overpotential for HER (70 mV, 90 mV, 81 mV at -10 mA cm-2) and OER (370 mV, 470 mV, 370 mV at 10 mA cm-2) in alkaline electrolyte, while the overpotential for HER is 176 mV, 189 mV, 167 mV at -10 mA cm-2 and corresponding OER is 290 mV, 390 mV, 300 mV at 10 mA cm-2 in simulated seawater, respectively. In addition, the NiFe, NiCo, CoFe-based electrolyzer acquire favorable overall water splitting activity in alkaline (1.72 V, 1.87 V, 1.66 V) and simulated seawater (1.73 V, 1.75 V, 1.69 V) at 10 mA cm-2. Overall, the above results authenticate the feasibility of developing autogenous heterostructure electrocatalysts for providing hydrogen and oxygen in alkaline and simulated seawater.

The Advances, Challenges, and Perspectives on Electrocatalytic Reduction of Nitrogenous Substances to Ammonia: A Review

Ammonia (NH3) is considered to be a critical chemical feedstock in agriculture, industry, and other fields. However, conventional Haber-Bosch (HB) ammonia (NH3) production suffers from high energy consumption, harsh reaction conditions, and large carbon dioxide emissions. Despite the emergence of electrocatalytic reduction of nitrogenous substances to NH3 under ambient conditions as a new frontier, there are several bottleneck problems that impede the commercialization process. These include low catalytic efficiency, competition with the hydrogen evolution reaction, and difficulties in breaking the N≡N triple bond. In this review, we explore the recent advances in electrocatalytic NH3 synthesis, using nitrogen and nitrate as reactants. We focus on the contribution of the catalyst design, specifically based on molecular-catalyst interaction mechanisms, as well as chemical bond breaking and directional coupling mechanisms, to address the aforementioned problems during electrocatalytic NH3 synthesis. Finally, we discuss the relevant opportunities and challenges in this field.

Design and Realization of Ni Clusters in MoS2@Ni/RGO Catalysts for Alkaline Efficient Hydrogen Evolution Reaction

Due to their almost zero relative hydrogen atom adsorption-free energy, MoS2-based materials have received substantial study. However, their poor electronic conductivity and limited number of catalytic active sites hinder their widespread use in hydrogen evolution reactions. On the other hand, metal clusters offer numerous active sites. In this study, by loading Ni metal clusters on MoS2 and combining them with the better electrical conductivity of graphene, the overpotential of the hydrogen evolution reaction was reduced from 165 mV to 92 mV at 10 mA·cm-2. This demonstrates that a successful method for effectively designing water decomposition is the use of synergistic interactions resulting from interfacial electron transfer between MoS2 and Ni metal clusters.

Enhanced NH3 Synthesis from Air in a Plasma Tandem-Electrocatalysis System Using Plasma-Engraved N-Doped Defective MoS2

We have developed a sustainable method to produce NH₃ directly from air using a plasma tandem-electrocatalysis system that operates via the N₂-NO_x-NH₃ pathway. To efficiently reduce NO₂^- to NH₃, we propose a novel electrocatalyst consisting of defective N-doped molybdenum sulfide nanosheets on vertical graphene arrays (N-MoS₂/VGs). We used a plasma engraving process to form the metallic 1T phase, N doping, and S vacancies in the electrocatalyst simultaneously. Our system exhibited a remarkable NH₃ production rate of 7.3 mg h^-1 cm^-2 at -0.53 V vs RHE, which is almost 100 times higher than the state-of-the-art electrochemical nitrogen reduction reaction and more than double that of other hybrid systems. Moreover, a low energy consumption of only 2.4 MJ mol_NH3^-1 was achieved in this study. Density functional theory calculations revealed that S vacancies and doped N atoms play a dominant role in the selective reduction of NO₂^- to NH₃. This study opens up new avenues for efficient NH₃ production using cascade systems.

Novel Strain Engineering Combined with a Microscopic Pore Synergistic Modulated Strategy for Designing Lattice Tensile-Strained Porous V2C-MXene for High-Performance Overall Water Splitting

Transition metal carbon/nitride (MXene) holds immense potential as an innovative electrocatalyst for enhancing the overall water splitting properties. Nevertheless, the re-stacking nature induced by van der Waals force remains a significant challenge. In this work, the lattice tensile-strained porous V₂C-MXene (named as TS₍₂₄₎-P₍₅₀₎-V₂C) is successfully constructed via the rapid spray freezing method and the following hydrothermal treatment. Besides, the influence of lattice strain degree and microscopic pores on the catalytic ability is reviewed and explored systematically. The lattice tensile strain within V₂C-MXene could widen the interlayer spacing and accelerate the ion transfer. The microscopic pores could change the ion transmission path and shorten the migration distance. As a consequence, the obtained TS₍₂₄₎-P₍₅₀₎-V₂C shows extraordinary hydrogen evolution reaction and oxygen evolution reaction activity with the overpotential of 154 and 269 mV, respectively, at the current density of 10 mA/cm², which is quite remarkable compared to the MXene-based electrocatalysts. Moreover, the overall water splitting device assembled using TS₍₂₄₎-P₍₅₀₎-V₂C as both anode and cathode demonstrates a low cell voltage requirement of 1.57 V to obtain 10 mA/cm². Overall, the implementation of this work could offer an exciting avenue to overcome the re-stacking issue of V₂C-MXene, affording a high-efficiency electrocatalyst with superior catalytic activity and desirable reaction kinetics.

Robust Copper-Based Nanosponge Architecture Decorated by Ruthenium with Enhanced Electrocatalytic Performance for Ambient Nitrogen Reduction to Ammonia

Electrochemical conversion of nitrogen to green ammonia is an attractive alternative to the Haber-Bosch process. However, it is currently bottlenecked by the lack of highly efficient electrocatalysts to drive the sluggish nitrogen reduction reaction (N₂RR). Herein, we strategically design a cost-effective bimetallic Ru-Cu mixture catalyst in a nanosponge (NS) architecture via a rapid and facile method. The porous NS mixture catalysts exhibit a large electrochemical active surface area and enhanced specific activity arising from the charge redistribution for improved activation and adsorption of the activated nitrogen species. Benefiting from the synergistic effect of the Cu constituent on morphology decoration and thermodynamic suppression of the competing hydrogen evolution reaction, the optimized Ru_0.15Cu_0.85 NS catalyst presents an impressive N₂RR performance with an ammonia yield rate of 26.25 μg h^-1 mg_cat.^-1 (corresponding to 10.5 μg h^-1 cm^-2) and Faradic efficiency of 4.39% as well as superior stability in alkaline medium, which was superior to that of monometallic Ru and Cu nanostructures. Additionally, this work develops a new bimetallic combination of Ru and Cu, which promotes the strategy to design efficient electrocatalysts for electrochemical ammonia production under ambient conditions.

Zinc Vanadate (Zn3V2O8) Immobilized Multiwall Carbon Nanotube (MWCNT) Heterojunction as an Efficient Photocatalyst for Visible Light Driven Hydrogen Production

Z-scheme photocatalytic reaction is considered an effective strategy to promote the photogenerated electron-hole separation for significantly improving the efficiency of photocatalytic hydrogen precipitation from splitting water. In this study, a heterojunction nanocomposite material based on Zn₃V₂O₈ (ZV) with MWCNT was prepared by a hydrothermal process. The photocatalysts were characterized by X-ray diffraction, scanning electron microscopy (SEM), Fourier transform infrared (FTIR), UV-visible absorption spectroscopy, and transmission electron microscopy (TEM) to understand crystal structure, morphology, and optical properties. The efficiency of the samples was evaluated for the photocatalytic H₂ production under visible solar radiation using water glycerol as a sacrificial reagent. The obtained results suggest that, between ZV and ZV@MWCNT, the latter shows higher efficiency for H₂ production. The maximum H₂ production efficiency was found to be 26.87 μmol g^-1 h^-1 for ZV and 99.55 μmol g^-1 h^-1 for ZV@MWCNT. The synergistic effect of MWCNT to ZV resulted in improving the efficiency of charges and light-absorbing capacity, resulting in enhanced H₂ production in the heterojunction nanocomposite material. The nanocomposite was stable and highly efficient for H₂ production of six or more cycles. Based on the outcomes of this study, it can be observed that forming the heterojunction of individual nano systems could result in more efficient material for H₂ production under visible solar energy.

Heterostructured Bi2S3/MoS2 Nanoarrays for Efficient Electrocatalytic Nitrate Reduction to Ammonia Under Ambient Conditions

Developing efficient electrocatalysts to realize the nitrate reduction reaction (eNO₃^-RR) for ammonia synthesis as an alternative to the traditional Haber-Bosch production process is of great significance. Herein, the heterostructured Bi₂S₃/MoS₂ nanoarrays were successfully synthesized by Bi₂S₃ nanowires anchored on MoS₂ nanosheets. Owing to the interfacial coupling effect, both particular surface area and exposure active sites increase. Density functional theory further uncovered that the excellent activity originates from charge transfer of the interface and a low potential barrier of 0.58 eV for hydrogenation of *NO to *NOH on Bi₂S₃/MoS₂. Compared with pure Bi₂S₃ and MoS₂ catalysts, the heterostructured Bi₂S₃/MoS₂ nanoarrays exhibit a superior NH₃ yield of 15.04 × 10^-2 mmol·h^-1·cm^-2 and a Faraday efficiency of 88.4% at -0.8 V versus the reversible hydrogen electrode. This work provides a new avenue to explore advanced electrocatalysts, which is expected to shorten the distance from the practical application of the eNO₃^-RR technology.

Synergistic Interaction of MoS2 Nanoflakes on La2Zr2O7 Nanofibers for Improving Photoelectrochemical Nitrogen Reduction

Ammonia is a suitable hydrogen carrier with each molecule accounting for up to 17.65% of hydrogen by mass. Among various potential ammonia production methods, we adopt the photoelectrochemical (PEC) technique, which uses solar energy as well as electricity to efficiently synthesize ammonia under ambient conditions. In this article, we report MoS₂@La₂Zr₂O₇ heterostructures designed by incorporating two-dimensional (2D)-MoS₂ nanoflakes on La₂Zr₂O₇ nanofibers (MoS₂@LZO) as photoelectrocatalysts. The MoS₂@LZO heterostructures are synthesized by a facile hydrothermal route with electrospun La₂Zr₂O₇ nanofibers and Mo precursors. The MoS₂@LZO heterostructures work synergistically to amend the drawbacks of the individual MoS₂ electrocatalysts. In addition, the harmonious activity of the mixed phase of pyrochlore/defect fluorite-structured La₂Zr₂O₇ nanofibers generates an interface that aids in increased electrocatalytic activity by enriching oxygen vacancies in the system. The MoS₂@LZO electrocatalyst exhibits an enhanced Faradaic efficiency and ammonia yield of approximately 2.25% and 10.4 μg h^-1 cm^-2, respectively, compared to their corresponding pristine samples. Therefore, the mechanism of improving the PEC ammonia production performance by coupling oxygen-vacant sites to the 2D-semiconductor-based electrocatalysts has been achieved. This work provides a facile strategy to improve the activity of PEC catalysts by designing an efficient heterostructure interface for PEC applications.

Electron coupled FeS2/MoS2 heterostructure for efficient electrocatalytic ammonia synthesis under ambient conditions

Developing efficient ammonia synthesis technology under ambient conditions is of vital importance. In this work, an FeS₂ coupled MoS₂ heterostructure with ultrathin features was designed by a one-step hydrothermal process for the electrochemical nitrogen reduction reaction. Density functional theory calculations reveal that the electronic structure of MoS₂ greatly changes with the introduction of FeS₂. The modulated electronic structure of MoS₂ not only exhibits enhanced conductivity but also facilitates the activation of N₂ molecules due to its abundant electronic region. The optimized FeS₂/MoS₂ nanosheet heterostructure achieves a high NH₃ yield rate of 2.59 μmol h^-1 mg^-1 and a FE of 4.63% at -0.3 V vs. RHE. Besides, the well-designed nanocomposite also shows excellent selectivity without N₂H₄ by-products and exhibits good stability after electrocatalysis for 48 hours.

All Transition Metal Selenide Composed High-Energy Solid-State Hybrid Supercapacitor

Transition metal selenides (TMSs) have enthused snowballing research and industrial attention due to their exclusive conductivity and redox activity features, holding them as great candidates for emerging electrochemical devices. However, the real-life utility of TMSs remains challenging owing to their convoluted synthesis process. Herein, a versatile in situ approach to design nanostructured TMSs for high-energy solid-state hybrid supercapacitors (HSCs) is demonstrated. Initially, the rose-nanopetal-like NiSe@Cu₂ Se (NiCuSe) positive electrode and FeSe nanoparticles negative electrode are directly anchored on Cu foam via in situ conversion reactions. The complementary potential windows of NiCuSe and FeSe electrodes in aqueous electrolytes associated with the excellent electrical conductivity results in superior electrochemical features. The solid-state HSCs cell manages to work in a high voltage range of 0-1.6 V, delivers a high specific energy density of 87.6 Wh kg^-1 at a specific power density of 914.3 W kg^-1 and excellent cycle lifetime (91.3% over 10 000 cycles). The innovative insights and electrode design for high conductivity holds great pledge in inspiring material synthesis strategies. This work offers a feasible route to develop high-energy battery-type electrodes for next-generation hybrid energy storage systems.

A series of POM-based compounds by tuning coordination groups and spacers of ligands: electrocatalytic, capacitive and photoelectrocatalytic properties

A series of POM-based compounds can be used as amperometric detectors for NO2− and Cr(vi). They also have capacitive properties and can effect the high-efficiency photoelectrocatalytic degradation of organic dyes.

A series of POM compounds constructed using a flexible ligand containing three coordination groups: electrocatalytic and photocatalytic reduction and amperometric detection of Cr(vi)

Four polyoxometalate-based compounds can be used as electrocatalysts and electrochemical sensors for amperometric detection of NO2− and Cr(VI), and also have the performance of photocatalytic reduction of Cr(VI).

A series of polyoxometalate compounds by tuning N sites and numbers of ligands: syntheses, characterization and electrochemical sensing, and photocatalytic and supercapacitor properties

Using morpholine derivatives with different N sites and numbers, we synthesized seven compounds by a hydrothermal method. They can photocatalytically degrade organic dyes and reduce Cr(vi) and can be used as electrochemical sensors. 4 has capacitor performance.

POM-based compounds modified by mono- and bis-triazole derivatives: photocatalytic, electrochemical, and supercapacitor properties

Using triazole derivatives 5 POM-based compounds with electrocatalytic and capacitive properties were obtained under hydrothermal conditions. The compounds have good photocatalytic activity for the degradation of organic dyes and the reduction of Cr(vi).