Interface-Induced Self-Assembly Strategy Toward 2D Ordered Mesoporous Carbon/MXene Heterostructures for High-Performance Supercapacitors

Ordered Mesoporous Carbon Featuring Single-Crystal Morphology and Tunable Pore Architectures via EtOH-Mediated Micelle Assembly

The precise control of reaction kinetics and the synchronous regulation of the micelle assembly in the soft-templating method for synthesizing ordered mesoporous carbon presents a significant challenge. In this study, a versatile ethanol-mediated self-assembly strategy is introduced to synthesize ordered mesoporous carbons (OMCs) with diverse morphologies and well-defined mesostructures using liquefied wood (LW). Ethanol functions as both a proton-trapping agent and a linker between carbon precursors and templates, enabling fine-tuned regulation of the self-assembly kinetics while providing additional hydrogen bonding interactions. Furthermore, the micelle structure can be precisely manipulated from cylindrical to spherical through ethanol-induced selective swelling of hydrophilic blocks, resulting in a reduction in packing parameter (p) from 1/3 < (p) < 1/2 to (p) ≤ 1/3. Notably, the spherical composite micelles self-assemble into single crystals with highly ordered body-centered mesostructures. The fabricated ordered mesoporous carbon single crystal (OMCSC) electrochemical sensing polymers exhibit absolute enantiomeric discrimination for L- and D-tryptophan. This EtOH-mediated self-assembly approach not only elucidates the role of ethanol in the self-assembly process but also offers a promising pathway for fabricating versatile OMCs from renewable biomass resources.

Highly dispersed Ir nanoparticles on Ti3C2Tx MXene nanosheets for efficient oxygen evolution in acidic media

The industrialization of hydrogen production technology through polymer electrolyte membrane water splitting faces challenges due to high iridium (Ir) loading on the anode catalyst layer. While rational design of oxygen evolution reaction (OER) electrocatalysts aimed at effective iridium utilization is promising, it remains a challenging task. Herein, we present exfoliated Ti3C2Tx MXene as a highly conductive and corrosion-resistant support for acidic OER. We develop an alcohol reduction method to achieve uniform and dense loading of ultrafine Ir nanoparticles on the MXene surface. The IrO2/TiOx heterointerface is formed in situ on the Ir@Ti3C2Tx MXene surface, acting as a catalytically active phase for OER during electrocatalysis. The electron interactions at the IrO2/TiOx heterointerface create electron-rich Ir sites, which reduce the adsorption properties of oxygen intermediates and enhance intrinsic OER activity. Consequently, the prepared Ir@Ti3C2Tx exhibits a mass activity that is 7 times greater than that of the benchmark IrO2 catalyst for OER in acidic media. In addition, the /Ti3C2Tx MXene support can stabilize the Ir nanoparticles, so that the stability number of Ir@Ti3C2Tx MXene is about 2.4 times higher than that of the IrO2 catalyst.

One pot synthesis of poly m-toluidine incorporated silver and silver oxide nanocomposite as a promising electrode for supercapacitor devices

The design and fabrication of novel electrodes with strong electrochemical responses are crucial in advanced supercapacitor technology. In this study, a poly(m-toluidine)/silver-silver oxide (PMT/Ag-Ag2O) nanocomposite was prepared using the photopolymerization method. Various characterization techniques were employed to analyze the prepared nanomaterials. The resulting structure of Ag-Ag2O minimizes ion diffusion distances, increases active sites, and accelerates redox reactions. The electrochemical response of PMT and PMT/Ag-Ag2O electrodes was evaluated in three different electrolyte solutions (Na2SO4, H2SO4, and HCl). The specific capacitance of PMT/Ag-Ag2O nanocomposite was found to be higher than that of PMT alone. Among the tested electrolytes, HCl exhibited the highest specific capacitance of 443 F g-1 at a gravimetric current density of 0.4 A g-1, surpassing H2SO4 (104 F g-1) and Na2SO4 (32 F g-1). Also, the PMT/Ag-Ag2O nanocomposite has demonstrated good cycling stability. It exhibited a high specific power density of 156 W Kg-1 and a specific energy density of 1.8 Wh Kg-1. These results highlight the potential of the prepared PMT/Ag-Ag2O nanocomposite as a nanoelectrode material for high-performance supercapacitors.

An In Situ Oxidative Polymerization Method to Synthesize Mesoporous Polypyrrole/MnO2 Composites for Supercapacitors

Manganese dioxide (MnO2) shows great potential in the field of electrochemical performance. But its poor conductivity, easy dissolution in electrolytes and undesirable ionic accessibility hinder its application. The construction of mesoporous polypyrrole/manganese dioxide (PPy/MnO2) composites can effectively alleviate these problems. Herein, an in situ oxidative polymerization method is developed to synthesize mesoporous PPy/MnO2 composites. In this method, Pluronic P123 and pyrrole monomers are co-assembled on the surface of MnO2. MnO2 is used as an oxidation initiator to polymerize pyrrole under acidic conditions and as a substrate for a uniform coating of PPy. The obtained composites, with a large electrochemical effective area, more reaction sites and good structural stability have better capacitor performance (182.8 F g-1), higher than MnO2 (116.6 F g-1) at the same current density. This method provides a meaningful reference for the development of mesoporous PPy/MnO2 supercapacitor materials.

Progress and Perspective in harnessing MXene-carbon-based composites (0-3D): Synthesis, performance, and applications

MXene is recognized as a promising catalyst for versatile applications due to its abundant metal sites, physicochemical properties, and structural formation. This comprehensive review offers an in-depth analysis of the incorporation of carbon into MXene, resulting in the formation of MXene-carbon-based composites (MCCs). Pristine MXene exhibits numerous outstanding characteristics, such as its atomically thin 2D structure, hydrophilic surface nature, metallic electrical conductivity, and substantial specific surface area. The introduction of carbon guides the assembly of MCCs through electrostatic self-assembly, pairing positively charged carbon with negatively charged MXene. These interactions result in increased interlayer spacing, reduced ion/electron transport distances, and enhanced surface hydrophilicity. Subsequent sections delve into the synthesis methods for MCCs, focusing on MXene integrated with various carbon structures, including 0D, 1D, 2D, and 3D carbon. Comprehensive discussions explore the distinctive properties of MCCs and the unique advantages they offer in each application domain, emphasizing the contributions and advancements they bring to specific fields. Furthermore, this comprehensive review addresses the challenges encountered by MCCs across different applications. Through these analyses, the review promotes a deeper understanding of exceptional characteristics and potential applications of MCCs. Insights derived from this review can serve as guidance for future research and development efforts, promoting the widespread utilization of MCCs across a broad spectrum of disciplines and spurring future innovations.

Pyridinic Nitrogen Sites Dominated Coordinative Engineering of Subnanometric Pd Clusters for Efficient Alkynes' Semihydrogenation

Supported metal catalysts have played an important role in optimizing selective semihydrogenation of alkynes for fine chemicals. There into, nitrogen-doped carbons, as a type of promising support materials, have attracted extensive attentions. However, due to the general phenomenon of random doping for nitrogen species in the support, it is still atremendous challenge to finely identify which nitrogen configuration dominates the catalytic property of alkynes' semihydrogenation. Herein, it is reported that uniform mesoporous N-doped carbon spheres derived from mesoporous polypyrrole spheres are used as supports to immobilized subnanometric Pd clusters, which provide a particular platform to research the influence of nitrogen configurations on the alkynes' semihydrogenation. Comprehensive experimental results and density functional theory calculation indicate that pyridinic nitrogen configuration dominates the catalytic behavior of Pd clusters. The high contents of pyridinic nitrogen sites offer abundant coordination sites, which greatly reduces the energy barrier of the rate-determining reaction step and makes Pd clusters own high catalytic activity. The electron effect between pyridinic nitrogen sites and Pd clusters makes the reaction highly selective. Additionally, the good mesostructures also promote the fast transport of substrate. Based on the above, catalyst Pd@PPy-600 exhibits high catalytic activity (99%) and selectivity (96%) for phenylacetylene (C₈ H₆ ) semihydrogenation.

Ordered Mesoporous Carbon Grafted MXene Catalytic Heterostructure as Li-Ion Kinetic Pump toward High-Efficient Sulfur/Sulfide Conversions for Li-S Battery

Lithium-sulfur (Li-S) batteries exhibit unparalleled theoretical capacity and energy density than conventional lithium ion batteries, but they are hindered by the dissatisfactory "shuttle effect" and the sluggish conversion kinetics owing to the low lithium ion transport kinetics, resulting in rapid capacity fading. Herein, a catalytic two-dimensional heterostructure composite is prepared by evenly grafting mesoporous carbon on the MXene nanosheet (denoted as OMC-g-MXene), serving as interfacial kinetic accelerators in Li-S batteries. In this design, the grafted mesoporous carbon in the heterostructure can not only prevent the stack of MXene nanosheets with the enhanced mechanical property but also offer a facilitated pump for accelerating ion diffusion. Meanwhile, the exposed defect-rich OMC-g-MXene heterostructure inhibits the polysulfide shuttling with chemical interactions between OMC-g-MXene and polysulfides and thus simultaneously enhances the electrochemical conversion kinetics and efficiency, as fully investigated by in situ/ex situ characterizations. Consequently, the cells with OMC-g-MXene ion pumps achieve a high cycling capacity (966 mAh g-1 at 0.2 C after 200 cycles), a superior rate performance (537 mAh g-1 at 5 C), and an ultralow decaying rate of 0.047% per cycle after 800 cycles at 1 C. Even employed with a high sulfur loading of 7.08 mg cm-2 under lean electrolyte, an ultrahigh areal capacity of 4.5 mAh cm-2 is acquired, demonstrating a future practical application.

Crystalline phase transformation of Co-MOF derivatives on ordered mesoporous carbons for high-performance supercapacitor applications

Preparation and phase transformation of Co-based metal–organic frameworks derivatives.

Multi-Dimensional Molecular Self-Assembly Strategy for the Construction of Two-Dimensional Mesoporous Polydiaminopyridine and Carbon Materials

Two-dimensional (2D) mesoporous polymers, combining the advantages of organic polymers, porous materials, and 2D materials, have received great attention in adsorption, catalysis, and energy storage. However, the synthesis of 2D mesoporous polymers is not only challenged by the complex 2D structure construction, but also by the low yield and difficulty in controlling the dynamics of the assembly during the generation of mesopores. Herein, a facile multi-dimensional molecular self-assembly strategy is reported for the preparation of 2D mesoporous polydiaminopyridines (MPDAPs), which features tunable pore sizes (17-35 nm) and abundant N content up to 18.0 at%. Benefitting from the abundant N sites, 2D nanostructure, and uniform-large mesopores, the 2D MPDAPs exhibit excellent catalytic performance for the Knoevenagel condensation reaction. After calcination under N₂ atmosphere, the obtained 2D N-doped mesoporous carbon (NMCs) with large and uniform pore sizes, high surface areas, abundant N content (up to 23.1%), and a high ratio of basic N species (57.0% pyridinic N and 35.9% pyrrolic N) can show an excellent CO₂ uptake density (11.7 µmol m^-2 at 273 K), higher than previously reported porous materials.

Three-dimensional N-doped mesoporous carbon–MXene hybrid architecture for supercapacitor applications

NMC@MXene exhibits excellent rate capability as electrode material for supercapacitors.

Modulation of MoS2 interlayer dynamics by in situ N-doped carbon intercalation for high-rate sodium-ion half/full batteries

In comparison with lithium-ion batteries, sodium-ion batteries (SIBs) have been proposed as an alternative for large-scale energy storage. However, finding an anode material that can overcome the sluggish electrochemical reaction kinetics and fast capacity fading caused by large volume expansion during cycling is problematic. In this study, the intercalation technique for nitrogen-doped carbon layers is implemented for the molybdenum disulfide (MoS₂/NC) structure to improve the rate and cycling stability of SIBs by increasing the diffusion rate of sodium ions and mitigating excessive volume structural expansion. The as-synthesized MoS₂/NC anode has a high discharge specific capacity of 546 mA h g^-1 at 1 A g^-1 after 160 cycles, as well as a high rate and stable cycle performance of 406 mA h g^-1 at 10 A g^-1 after 1000 cycles. Upon coupling with a high-voltage Na₃V₂(PO₄)₂O₂F cathode, the sodium-ion full battery displays high specific energies of 78.57 W h kg^-1 and 49.70 W h kg^-1 at specific powers of 193.76 W kg^-1 and 3756.80 W kg^-1, respectively, with commercialization potential demonstrated.