Hollow Cobalt-Based Bimetallic Sulfide Polyhedra for Efficient All-pH-Value Electrochemical and Photocatalytic Hydrogen Evolution

In Situ Formed Pt3Ti Nanoparticles on a Two-Dimensional Transition Metal Carbide (MXene) Used as Efficient Catalysts for Hydrogen Evolution Reactions

The design of efficient catalysts capable of delivering high currents at low overpotentials for hydrogen evolution reactions (HERs) is urgently needed to use catalysts in practical applications. Herein, we report platinum (Pt) alloyed with titanium (Ti) from the surface of Ti₃C₂T_x MXenes to form Pt₃Ti intermetallic compound (IMC) nanoparticles (NPs) via in situ coreduction. In situ X-ray absorption spectroscopy (XAS) indicates that Pt undergoes a temperature-dependent transformation from single atoms to intermetallic compounds, and the catalyst reduced at 550 °C exhibits a superior HER performance in acidic media. The Pt/Ti₃C₂T_x-550 catalyst outperforms commercial Pt/Vulcan and has a small overpotential of 32.7 mV at 10 mA cm^-2 and a low Tafel slope of 32.3 mV dec^-1. The HER current was normalized by the mass and dispersion of Pt, and the mass activity and specific activity of Pt/Ti₃C₂T_x-550 are 4.4 and 13 times higher, respectively, than those of Pt/Vulcan at an overpotential of 70 mV. The density functional theory (DFT) calculations suggest that the (111)- and (100)-terminated Pt₃Ti nanoparticles exhibit *H binding comparable to Pt(111), while the (110) termination has an *H adsorption that is too exergonic, thus poisoned in the low overpotential region. This work demonstrates the potential of MXenes as platforms for the design of electrocatalysts and may spur future research for other MXene-supported metal catalysts that can be used for a wide range of electrocatalytic reactions.

Stimulated Electrocatalytic Hydrogen Evolution Activity of MOF-Derived MoS2 Basal Domains via Charge Injection through Surface Functionalization and Heteroatom Doping

The design of MoS2-based electrocatalysts with exceptional reactivity and robustness remains a challenge due to thermodynamic instability of active phases and catalytic passiveness of basal planes. This study details a viable in situ reconstruction of zinc-nitrogen coordinated cobalt-molybdenum disulfide from structure directing metal-organic framework (MOF) to constitute specific heteroatomic coordination and surface ligand functionalization. Comprehensive experimental spectroscopic studies and first-principle calculations reveal that the rationally designed electron-rich centers warrant efficient charge injection to the inert MoS2 basal planes and augment the electronic structure of the inactive sites. The zinc-nitrogen coordinated cobalt-molybdenum disulfide shows exceptional catalytic activity and stability toward the hydrogen evolution reaction with a low overpotential of 72.6 mV at -10 mA cm-2 and a small Tafel slope of 37.6 mV dec-1. The present study opens up a new opportunity to stimulate catalytic activity of the in-plane MoS2 basal domains for enhanced electrochemistry and redox reactivity through a "molecular reassembly-to-heteroatomic coordination and surface ligand functionalization" based on highly adaptable MOF template.

A Critical Review on Enhancement of Photocatalytic Hydrogen Production by Molybdenum Disulfide: From Growth to Interfacial Activities

Ultrathin 2D molybdenum disulfide (MoS₂ ), which is the flagship of 2D transition-metal dichalcogenide nanomaterials, has drawn much attention in the last few years. 2D MoS₂ has been banked as an alternative to platinum for highly active hydrogen evolution reaction because of its low cost, high surface-to-volume ratio, and abundant active sites. However, when MoS₂ is used directly as a photocatalyst, contrary to public expectation, it still performs poorly due to lateral size, high recombination ratio of excitons, and low optical cross section. Besides, simply compositing MoS₂ as a cocatalyst with other semiconductors cannot satisfy the practical application, which stimulates the pursual of a comprehensive insight into recent advances in synthesis, properties, and enhanced hydrogen production of MoS₂ . Therefore, in this Review, emphasis is given to synthetic methods, phase transitions, tunable optical properties, and interfacial engineering of 2D MoS₂ . Abundant ways of band edge tuning, structural modification, and phase transition are addressed, which can generate the neoteric photocatalytic systems. Finally, the main challenges and opportunities with respect to MoS₂ being a cocatalyst and coherent light-matter interaction of MoS₂ in photocatalytic systems are proposed.

Hierarchical MoS2 Hollow Architectures with Abundant Mo Vacancies for Efficient Sodium Storage

Achieving a molecular level understanding of surface performance of nanomaterials by modulating the electronic structure is important but challenging. Here, we have developed a hollow microcube framework constructed by Mo-defect-rich ultrathin MoS₂ nanosheets (HMF-MoS₂) through a zeolite-like-framework-engaged strategy. The hollow structured HMF-MoS₂ delivers an impressive specific capacity (384.3 mA h g^-1 after 100 cycles at 100 mA g^-1) and cycle stability (267 mA h g^-1 after 125 cycles at 1 A g^-1) for sodium storage. As evidenced by experiments and density functional theory calculations, abundant Mo vacancies in MoS₂ can greatly accelerate the charge transfer and enhance the interaction between MoS₂ and sodium, resulting in the promotion of sodium storage. Kinetic analysis result reveals that the ultrafast sodium ion storage of HMF-MoS₂ could be associated with the significant contribution of capacitive energy storage. This work highlights the detailed molecular level understanding of chemical reaction on MoS₂ surface by defect and morphology engineering, which can be applied to other metal sulfides for energy storage devices.

Self-Sacrificial Template-Directed Vapor-Phase Growth of MOF Assemblies and Surface Vulcanization for Efficient Water Splitting

Direct use of metal-organic frameworks (MOFs) with robust pore structures, large surface areas, and high density of coordinatively unsaturated metal sites as electrochemical active materials is highly desirable (rather than using as templates and/or precursors for high-temperature calcination), but this is practically hindered by the poor conductivity and low accessibility of active sites in the bulk form. Herein, a universal vapor-phase method is reported to grow well-aligned MOFs on conductive carbon cloth (CC) by using metal hydroxyl fluorides with diverse morphologies as self-sacrificial templates. Specifically, by further partially on-site generating active Co₃ S₄ species from Co ions in the echinops-like Co-based MOF (EC-MOF) through a controlled vulcanization approach, the resulting Co₃ S₄ /EC-MOF hybrid exhibits much enhanced electrocatalytic performance toward the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), with overpotentials of 84 and 226 mV required to reach a current density of 10 mA cm^-2 , respectively. Density functional theory (DFT) calculations and experimental results reveal that the electron transfer between Co₃ S₄ species and EC-MOF can decrease the electron density of the Co d-orbital, resulting in more electrocatalytically optimized adsorption properties for Co. This study will open up a new avenue for designing highly ordered MOF-based surface active materials for various electrochemical energy applications.

Morphology-Controlled Metal Sulfides and Phosphides for Electrochemical Water Splitting

Because H₂ is considered a promising clean energy source, water electrolysis has attracted great interest in related research and technology. Noble-metal-based catalysts are used as electrode materials in water electrolyzers, but their high cost and low abundance have impeded them from being used in practical areas. Recently, metal sulfides and phosphides based on earth-abundant transition metals have emerged as promising candidates for efficient water-splitting catalysts. Most studies have focused on adjusting the composition of the metal sulfides and phosphides to enhance the catalytic performance. However, morphology control of catalysts, including faceted and hollow structures, is much less explored for these systems because of difficulties in the synthesis, which requires a deep understanding of the nanocrystal growth process. Herein, representative synthetic methods for morphology-controlled metal sulfides and phosphides are introduced to provide insights into these methodologies. The electrolytic performance of morphology-controlled metal sulfide- and phosphide-based nanocatalysts with enhanced surface area and intrinsically high catalytic activity is also summarized and the future research directions for this promising catalyst group is discussed.

Nanoarchitectonics for Transition-Metal-Sulfide-Based Electrocatalysts for Water Splitting

Heterogenous electrocatalysts based on transition metal sulfides (TMS) are being actively explored in renewable energy research because nanostructured forms support high intrinsic activities for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Herein, it is described how researchers are working to improve the performance of TMS-based materials by manipulating their internal and external nanoarchitectures. A general introduction to the water-splitting reaction is initially provided to explain the most important parameters in accessing the catalytic performance of nanomaterials catalysts. Later, the general synthetic methods used to prepare TMS-based materials are explained in order to delve into the various strategies being used to achieve higher electrocatalytic performance in the HER. Complementary strategies can be used to increase the OER performance of TMS, resulting in bifunctional water-splitting electrocatalysts for both the HER and the OER. Finally, the current challenges and future opportunities of TMS materials in the context of water splitting are summarized. The aim herein is to provide insights gathered in the process of studying TMS, and describe valuable guidelines for engineering other kinds of nanomaterial catalysts for energy conversion and storage technologies.

Hollow Functional Materials Derived from Metal-Organic Frameworks: Synthetic Strategies, Conversion Mechanisms, and Electrochemical Applications

Hollow materials derived from metal-organic frameworks (MOFs), by virtue of their controllable configuration, composition, porosity, and specific surface area, have shown fascinating physicochemical properties and widespread applications, especially in electrochemical energy storage and conversion. Here, the recent advances in the controllable synthesis are discussed, mainly focusing on the conversion mechanisms from MOFs to hollow-structured materials. The synthetic strategies of MOF-derived hollow-structured materials are broadly sorted into two categories: the controllable synthesis of hollow MOFs and subsequent pyrolysis into functional materials, and the controllable conversion of solid MOFs with predesigned composition and morphology into hollow structures. Based on the formation processes of hollow MOFs and the conversion processes of solid MOFs, the synthetic strategies are further conceptually grouped into six categories: template-mediated assembly, stepped dissolution-regrowth, selective chemical etching, interfacial ion exchange, heterogeneous contraction, and self-catalytic pyrolysis. By analyzing and discussing 14 types of reaction processes in detail, a systematic mechanism of conversion from MOFs to hollow-structured materials is exhibited. Afterward, the applications of these hollow structures as electrode materials for lithium-ion batteries, hybrid supercapacitors, and electrocatalysis are presented. Finally, an outlook on the emergent challenges and future developments in terms of their controllable fabrications and electrochemical applications is further discussed.

Ultrathin Co9S8 nanosheets vertically aligned on N,S/rGO for low voltage electrolytic water in alkaline media

Development of hydrogen as clean and efficient energy carrier for future is imperative. Water electrolysis, is considered as one of the most promising ways to realize large-scaled hydrogen production. However, a big obstacle of it is to reduce the electric energy consumption for water oxidation in the anode. Engineering of hierarchical architectures on the electrocatalysts could provide abundant active sites and thus boost the sluggish reaction kinetics of water oxidation. Herein, a sequential synthesis method is developed for in-situ growth of ultrathin Co₉S₈ nanosheets vertically aligned on N and S co-doped reduced graphene oxide (Co₉S₈/N,S-rGO) as novel and efficient electrocatalysts for water splitting. This architecture with vertically aligned ultrathin Co₉S₈ nanosheets on N,S/rGO is adopted to facilitate the electron transport and exposure of active sites. Benefiting from the synergetic catalysis between Co₉S₈ nanosheets and N,S/rGO, Co₉S₈/N,S-rGO presents remarkable electrocatalytic activity towards oxygen evolution with a low overpotential (266 mV to achieve current density of 10 mA cm⁻²), small Tafel slope of 75.5 mV dec⁻¹, and good durability in alkaline medium. This remarkable OER electrocatalytic activity is outperforms most of the known noble-metal-free electrocatalysts.

Three-Dimensional Nanoporous Co9S4P4 Pentlandite as a Bifunctional Electrocatalyst for Overall Neutral Water Splitting

Significant progress has recently been achieved in developing noble-metal-free catalysts for electrochemical water splitting in acidic and alkaline electrolytes. However, high-performance bifunctional catalysts toward both hydrogen evolution and oxygen oxidation reactions of neutral water have not been realized in spite of the technical importance for electrochemical hydrogen production in natural environments powered by renewable energy sources of wind, solar, and so on. Here, we report a nanoporous Co₉S₄P₄ pentlandite with three-dimensional bicontinuous nanoporosity for electrochemical water splitting in neutral solutions. The three-dimensional binder-free catalyst shows a negligible onset overpotential, low Tafel slope, and excellent poisoning tolerance for hydrogen evolution reaction, comparable to or even better than commercial Pt catalysts. Remarkably, the new catalyst also has excellent catalytic activities toward oxygen evolution and, hence, can be used as both anode and cathode for overall neutral water splitting. These extraordinary catalytic activities toward neutral water splitting have never been obtained from non-noble-metal catalysts before. The bifunctional and low-cost catalyst holds great promise for practical applications in electrochemical water splitting in natural environments.

Recent Progress on Engineering Highly Efficient Porous Semiconductor Photocatalysts Derived from Metal-Organic Frameworks

Porous structures offer highly accessible surfaces and rich pores, which facilitate the exposure of numerous active sites for photocatalytic reactions, leading to excellent performances. Recently, metal-organic frameworks (MOFs) have been considered ideal precursors for well-designed semiconductors with porous structures and/or heterostructures, which have shown enhanced photocatalytic activities. In this review, we summarize the recent development of porous structures, such as metal oxides and metal sulfides, and their heterostructures, derived from MOF-based materials as catalysts for various light-driven energy-/environment-related reactions, including water splitting, CO₂ reduction, organic redox reaction, and pollution degradation. A summary and outlook section is also included.

Engineering additional edge sites on molybdenum dichalcogenides toward accelerated alkaline hydrogen evolution kinetics

The sluggish reaction kinetics of the hydrogen evolution reaction (HER) in alkaline media is a great obstacle to alkaline water electrolysis, and it remains a great challenge to develop precious metal-free efficient catalysts for the alkaline HER. Transition metal dichalcogenides (TMDs), in particular MoS2 and MoSe2, are promising catalysts for the HER in acidic media, but they exhibit much inferior catalytic activity for the alkaline HER owing to the slow water dissociation process. In this work, we, for the first time, demonstrate that TMD heterostructures with abundant edge sites deliver substantially accelerated alkaline HER kinetics, which is in great part due to the enhanced water adsorption/dissociation capability. As a proof of concept, MoS2/MoSe2 heterostructures with ultrasmall MoS2 nanoclusters anchored on MoSe2 nanosheets are synthesized via a solution-phase process and are investigated as alkaline HER catalysts in detail. MoSe2 nanosheets serve as excellent substrates to hinder the agglomeration of MoS2 nanoclusters, resulting in abundant edge sites. Benefiting from the decent water adsorption/dissociation capability of the edge sites, the optimal MoS2/MoSe2 heterostructure shows exceptional catalytic activity in 1 M KOH with an overpotential of 235 mV at 10 mA cm-2 and a Tafel slope of 96 mV dec-1, which is substantially improved as compared with the individual MoSe2 (330 mV, 135 mV dec-1) and MoS2 (400 mV, 157 mV dec-1). The success of this catalyst design strategy for enhancing alkaline HER kinetics is also demonstrated in MoSe2/MoSe2 and MoS2/MoS2 heterostructures. The results suggest that engineering additional edge sites that have a strong affinity for H2O is critical for TMDs towards enhanced alkaline HER activity, and also open new avenues in the design of precious metal-free efficient catalysts for the alkaline HER.

Hollow core–shell NiCo2S4@MoS2 dodecahedrons with enhanced performance for supercapacitors and hydrogen evolution reaction

Hollow core–shell NiCo₂S₄@MoS₂ heterostructures were fabricated using zeolitic imidazolate frameworks as templates and exhibited enhanced electrochemical performance for supercapacitors and hydrogen evolution reaction.

Conductive Ti3C2 and MOF-derived CoSx boosting the photocatalytic hydrogen production activity of TiO2

We report a novel TiO₂ nanocrystals photocatalyst confined by ZIF-67-templated porous CoS_x, with conductive Ti₃C₂ boosting the transport efficiency of the charge carriers.

Recent advances in metal sulfides: from controlled fabrication to electrocatalytic, photocatalytic and photoelectrochemical water splitting and beyond

This review describes an in-depth overview and knowledge on the variety of synthetic strategies for forming metal sulfides and their potential use to achieve effective hydrogen generation and beyond.

A robust CdS/In2O3 hierarchical heterostructure derived from a metal–organic framework for efficient visible-light photocatalytic hydrogen production

CdS/In₂O₃ hierarchical nanotubes with intimate and extensive contact between CdS and In₂O₃ were synthesized from a MOF and showed huge improvement of visible-light photocatalytic hydrogen production.

Seleno-analogues of pentlandites (Fe4.5Ni4.5S8−YSeY, Y = 1–6): tuning bulk Fe/Ni sulphoselenides for hydrogen evolution

A series of hitherto unprecedented seleno-pentlandites (Fe_4.5Ni_4.5S_8-YSe_Y) and their catalytic activity in the hydrogen evolution reaction is presented.

Design of Mo-doped cobalt sulfide hollow nanocages from zeolitic imidazolate frameworks as advanced electrodes for supercapacitors

A Mo-doped CoS HNC with enhanced electrochemical performance was designed by using ZIF-67 as a self-sacrificial template through a dissolution–regrowth process in the presence of NaMoO₄ with an additional sulfurization process.

Metal–organic framework assisted and in situ synthesis of hollow CdS nanostructures with highly efficient photocatalytic hydrogen evolution

Hollow CdS nanoboxes with a specific surface area of 153 m² g⁻¹ are synthesized through in situ sulfurizing Cd-MOF-47 with thiourea, which exhibit a greatly improved photocatalytic activity in water splitting to hydrogen (21 654 μmol g⁻¹ h⁻¹).

Properties of iron vanadate over CdS nanorods for efficient photocatalytic hydrogen production

In this study, V³⁺/VO²⁺/VO₂⁺ was successfully employed as a redox mediator to modify CdS nanorods for the first time, and remarkable enhancement of efficient hydrogen evolution was obtained.

A protective roasting strategy for preparation of stable mesoporous hollow CeO2 microspheres with enhanced catalytic activity for one-pot synthesis of imines from benzyl alcohols and anilines

A protective roasting strategy can be applied to prepare stable mh-CeO₂ microspheres with enhanced catalytic activity and reusability for one-pot synthesis of imines.

One-Dimensional Porous Hybrid Structure of Mo2C-CoP Encapsulated in N-Doped Carbon Derived from MOF: An Efficient Electrocatalyst for Hydrogen Evolution Reaction over the Entire pH Range

The development of outstanding noble-metal-free electrocatalysts for the hydrogen evolution reaction (HER) has attracted broad interest. Herein, a novel one-dimensional (1D) HER hybrid catalyst consisted of cobalt phosphide (CoP) and molybdenum carbide (Mo₂C) nanoparticles wrapped by nitrogen-doped graphitic carbon (called CoP/Mo₂C-NC) was successfully fabricated by a facile continuous-flow method and a simple two-step annealing process. During these processes, the successful synthesis of the MoO₃ nanorods coated with cobalt zeolitic imidazolate frameworks (Co-ZIF-67) (Co-ZIF-67@MoO₃) through the continuous-flow method plays a key role. The as-synthesized CoP/Mo₂C-NC hybrid electrocatalyst exhibits a significantly enhanced HER electrocatalytic activity over the entire pH range relative to that of the control materials CoP, Mo₂C-NC, and physically mixed CoP and Mo₂C-NC. The outstanding HER catalytic performance is mainly due to the fact that the electron cloud transfers from Co to Mo in CoP/Mo₂C-NC through the Co-P-Mo bond, resulting in the formation of a high valence state for Co (Co³⁺) species and lower valence states for Mo (i.e., Mo²⁺, Mo³⁺) species, providing the abundant HER active sites. Moreover, the Gibbs free energy (Δ G_H*) of CoP/Mo₂C-NC obtained by the density function theory calculations indicates a good balance between the Volmer and Heyrovsky/Tafel steps in HER kinetics. Such a cobalt zeolitic imidazolate framework-mediated strategy depicted in this work offers an interesting perspective for developing highly efficient noble-metal-free electrocatalysts for hydrogen production.

An Intriguing Pea-Like Nanostructure of Cobalt Phosphide on Molybdenum Carbide Incorporated Nitrogen-Doped Carbon Nanosheets for Efficient Electrochemical Water Splitting

The development of noble-metal-free, efficient, electrochemical, water-splitting catalyst systems has attracted considerable attention in recent times. In this study, a metal-organic framework based synthetic route to couple two non-noble-metal-based catalysts, CoP and Mo₂ C, supported on nitrogen-doped carbon has been developed. The strategy enables the formation of a nanohybrid with an attractive pea-like morphology, in which spherical CoP particles (≈10 nm) are embedded on two-dimensional nitrogen-doped carbon enriched with ultrafine Mo₂ C nanoparticles. This composition boosts the electrochemical alkaline water-splitting reaction by showing overpotentials (η₁₀ ) of only 94 and 265 mV for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), respectively, at a current density of 10 mA cm^-2 . Additionally, in an acidic medium, the η₁₀ values are 107 and 330 mV for HER and OER, respectively; this suggests good bifunctionality at both lower and higher pH levels. Overall water splitting has been demonstrated by the developed catalyst at a cell voltage of 1.64 V for a current density of 10 mA cm^-2 in alkaline medium, and a constant current is produced for more than 40 h under chronoamperometric conditions. This study describes the combination of two nanocomponents, with interconnected surface structures, which result in highly active and stable electrocatalytic performance.

Chemical Diversity of Metal Sulfide Minerals and Its Implications for the Origin of Life

Prebiotic organic synthesis catalyzed by Earth-abundant metal sulfides is a key process for understanding the evolution of biochemistry from inorganic molecules, yet the catalytic functions of sulfides have remained poorly explored in the context of the origin of life. Past studies on prebiotic chemistry have mostly focused on a few types of metal sulfide catalysts, such as FeS or NiS, which form limited types of products with inferior activity and selectivity. To explore the potential of metal sulfides on catalyzing prebiotic chemical reactions, here, the chemical diversity (variations in chemical composition and phase structure) of 304 natural metal sulfide minerals in a mineralogy database was surveyed. Approaches to rationally predict the catalytic functions of metal sulfides are discussed based on advanced theories and analytical tools of electrocatalysis such as proton-coupled electron transfer, structural comparisons between enzymes and minerals, and in situ spectroscopy. To this end, we introduce a model of geoelectrochemistry driven prebiotic synthesis for chemical evolution, as it helps us to predict kinetics and selectivity of targeted prebiotic chemistry under “chemically messy conditions”. We expect that combining the data-mining of mineral databases with experimental methods, theories, and machine-learning approaches developed in the field of electrocatalysis will facilitate the prediction and verification of catalytic performance under a wide range of pH and Eh conditions, and will aid in the rational screening of mineral catalysts involved in the origin of life.

Spherical Ruthenium Disulfide-Sulfur-Doped Graphene Composite as an Efficient Hydrogen Evolution Electrocatalyst

The exploition of cost-efficient and high-performance catalysts to boost hydrogen generation in overall water splitting is crucial to economically obtain green hydrogen energy. Herein, we propose a novel electrocatalyst consisting of spherical RuS₂ on S-doped reduced graphene oxide (s-RuS₂/S-rGO) with high catalytic behavior toward hydrogen evolution reaction (HER) in all pH conditions, especially in alkaline electrolytes. RuS₂/S-rGO delivers small overpotentials of 25 and 56 mV at current densities of 10 and 50 mA cm^-2, respectively, and a low Tafel slope of 29 mV dec^-1 with good stability for 100 h in basic solutions. This performance is comparable to and even exceeds that of documented representative electrocatalysts, including the benchmark Pt/C; since the price of Ru is about 1/25th that of Pt, this novel electrocatalyst offers a low-cost alternative to Pt-based HER electrocatalysts. Ruthenium-centered sites of RuS₂ in this hybrid catalyst are responsible for the HER active sites, and S doping in RuS₂ also exerts an important function for the HER activity; density functional theory calculations disclose that the water dissociation ability and adsorption free energy of hydrogen intermediate adsorption (Δ G_H*) for RuS₂ are very close to those of Pt. A homemade electrolyzer with an s-RuS₂/S-rGO (cathode)//RuO₂/C (anode) couple presents a relatively low voltage of 1.54 V at a current density of 20 mA cm^-2, while maintaining negligible deactivation over a 24 h operation.

Metal-organic framework derived leaf-like CoSNC nanocomposites for supercapacitor electrodes

The designed construction of micro-/nano-structures and multi-composites on electrodes showed a promising prospect to improve electrochemical properties in supercapacitors. Herein, a facile carbonizing strategy was adopted for fabricating leaf-like CoSNC nanocomposites, which possess both the sheet structure and multi-composites of well-dispersed CoS2 nanoparticles in N-doped carbon frameworks. First, the leaf-like nanocomposites with high aspect ratios effectively shortened the ion/electron transmission paths and exposed more faradaic redox sites. Second, the N-doped carbon frameworks could stabilize the electrode structure during charge/discharge processes. Third, the well-dispersed CoS2 nanoparticles could also enhance the electrochemical kinetics. Hence, leaf-like CoSNC nanocomposites as electrode materials exhibited high specific capacitance, good rate capacity and cycling stability.

Rapid Synthesis of Oxygen-Rich Covalent C2N (CNO) Nanosheets by Sacrifice of HKUST-1: Advanced Metal-Free Nanofillers for Polymers

A covalent oxygen-rich C₂N (CNO) network derived from metal-organic framework (HKUST-1) was innovatively synthesized by a rapid and green microwave irradiation method. This method can produce CNO multilayers efficiently, which paves a way for practical application of the nanosheets. Structural characterization and synthesis processes of CNO nanosheets were investigated to further understand the key role of HKUST-1. The as-prepared CNO has a layered feature, which theoretically favors to improve flame retardancy and mechanical performance of polymers. Desirable results were obtained as expected: the fire safety, antitensile, and impact resistance of polylactic acid (PLA) were prominently enhanced after adding CNO nanosheets, which can be attributed to the excellent dispersion and compatibility. PLA/CNO nanocomposite was self-distinguished at 2 wt % content of CNO, whereas the tensile strength was increased more than 36% compared with that of pure PLA, as well as the impact strength. This work broadens the application fields of CNO and endows it a possibility of actual application.

Metal-Organic-Framework-Derived Co3 S4 Hollow Nanoboxes for the Selective Reduction of Nitroarenes

MOF-derived Co₃ S₄ /CN hollow nanoboxes (CN=nitrogen-doped carbon) was used to catalyze the chemoselective reduction of nitroarenes to anilines under mild reaction conditions with H₂ as the reducing agent. The catalyst provides high conversion efficiencies and selectivities for a variety of nitroarene substrates that contain electron-donating or electron-withdrawing substituents under mild reaction conditions (in methanol at 60 °C). Further, the nanobox inhibits both dehalogenation and vinyl hydrogenation reactions, which are common limitations of state-of-the-art Pd-based catalysts. Because the reactions result in pure aniline products, the need for separation by column chromatography is eliminated. The resulting anilines are easily separated from the methanolic reaction solution in just three simple steps (centrifugation, decantation, and drying). If employed in industrial processes, catalysts of this kind would significantly reduce the amount of waste organic solvent generated and thus satisfy the need for sustainable chemical processes.

Crystalline Ru0.33 Se Nanoparticles-Decorated TiO2 Nanotube Arrays for Enhanced Hydrogen Evolution Reaction

Nowadays, the state-of-the-art electrocatalysts for hydrogen evolution reaction (HER) are platinum group metals. Nonetheless, Pt-based catalysts show decreased HER activity in alkaline media compared with that in acidic media due to the sluggish dissociation process of H₂ O on the surface of Pt. With a cost 1/25 that of Pt, Ru demonstrates a favorable dissociation kinetics of absorbed H₂ O. Herein, crystalline Ru_0.33 Se nanoparticles are decorated onto TiO₂ nanotube arrays (TNAs) to fabricate Ru_0.33 Se @ TNA hybrid for HER. Owing to the large-specific surface area, Ru_0.33 Se nanoparticles are freely distributed and the particle aggregation is eliminated, providing more active sites. The contracted electron transport pathway rendered by TiO₂ nanotubes and the synergistic effect at the interface significantly improve the charge transfer efficiency in the hybrid catalyst. Compared with Ru_0.33 Se nanoparticles deposited directly on the Ti foil (Ru_0.33 Se/Ti) or carbon cloth (Ru_0.33 Se/CC), Ru_0.33 Se @ TNA shows an enhanced catalytic activity with an overpotential of 57 mV to afford a current density of 10 mA cm^-2 , a Tafel slope of 50.0 mV dec^-1 . Furthermore, the hybrid catalyst also exhibits an outstanding catalytic stability. The strategy here opens up a new synthetic avenue to the design of highly efficient hybrid electrocatalysts for hydrogen production.