Strategic design of Fe and N co-doped hierarchically porous carbon as superior ORR catalyst: from the perspective of nanoarchitectonics

Multi-layered heterogeneous interfaces created in Co0.85Se@Ni3S4/NF to enhance supercapacitor performances by multi-step alternating electrodeposition

Heterogeneous interface construction is of far-reaching significance to optimize the electrochemical performance of electrodes. Herein, a multi-step alternating electrochemical deposition (MAED) method is proposed to alternately deposit Co0.85Se and Ni3S4 nanosheets on a nickel foam (NF), forming a special alternate layer-by-layer structure with multi-layered heterogeneous interfaces. The creation of the multi-layered heterogeneous interfaces provides a large interfacial area for redox reactions with optimum interstitials facilitating ion diffusion, thus greatly improving the electrochemical energy storage efficiency. With the increase in the layer number, the material exhibits increasingly better energy storage performance, and 8L-Co0.85Se@Ni3S4/NF exhibits the highest specific capacitances of 2508 F g-1 and 1558 F g-1 at a scan rate of 2 mV s-1 and a current density of 1 A g-1. The 8L-Co0.85Se@Ni3S4/NF//polypyrrole (PPy)/NF asymmetric supercapacitor provides a maximum operation potential window of 1.55 V and energy densities of 76.98 and 35.74 W h kg-1 when the power densities are 775.0 and 15 500 W kg-1, respectively, superior to most of the related materials reported. Through MAED, the deposited phase and the layer number can be accurately controlled, thus providing an efficient strategy for interface construction so as to increase the electrochemical activity of the energy storage materials.

Co-doping regulation on Ni-based electrocatalysts to adjust the selectivity of oxygen reduction reaction for Zn-air batteries and H2O2 production

Although Ni-based materials are widely used as electrocatalysts, it remains necessary to further explore their selectivity towards the four- or two-electron oxygen reduction reaction (ORR). Herein, it is proposed to synthesize NiO@NCNTs (NCNTs = N-doped carbon nanotubes) using a metal-organic framework (MOF), [Ni(BZIDA)(H2O)]n (NiMOF, BZIDA = benzimidazole-5,6-dicarboxylic acid), as a precursor after calcination with dicyandiamide (DCDA). Regarding NiO@NCNTs, small NiO particles are distributed in NCNTs derived from DCDA homogeneously. NiO@NCNTs act as a typical two-electron electrocatalyst. The H2O2 production rate of NiO@NCNTs reaches 0.5 mol g-1 h-1 at 0.46 V (vs. RHE). After the doping of Co2+ in NiMOF, Co/NiO@NCNTs were synthesized using a similar method, with the four-electron character shown in ORR. A Zn-air battery was assembled by applying Co/NiO@NCNTs as the cathode material. When discharge occurs at 5 and 10 mA cm-2, its specific capacitance reaches 779.3 and 832.2 mA h g-1 with an energy density of 928.6 and 948.5 W h kg-1, respectively. Theoretical calculations suggest a variation in ORR selectivity between NiO@NCNTs and Co/NiO@NCNTs, which results from their different interactions with OOH*. This study demonstrates the effect of the structure on ORR selectivity for Ni-based electrocatalysts.

Template Evolution Induced Relay Self-Assembly for Mesoporous Carbonaceous Materials via Hydrothermal Carbonization

Constructing carbonaceous materials with versatile surface structures still remains a great challenge due to limited self-assembly methods, especially at high temperatures. This study presents an innovative template evolution induced relay self-assembly (TEIRSA) for the fabrication of large polyoxometalate (POM)-mixed carbonaceous nanosheets featuring surface mesoporous structures through hydrothermal carbonization (HTC). The method employs POM and acetone as additives, cleverly modulating the Ostwald ripening-like process of P123-based micelles, effectively addressing the instability challenges inherent in traditional soft-template methods, especially within the demanding carbohydrate HTC process. Additionally, this method allows for the independent regulation of surface architectures through the selection of organic additives. The resulting nanosheets exhibit diverse surface morphologies, including surface spherical mesopores, 1D open channels, and smooth surfaces. Their unexpectedly versatile properties have swiftly garnered recognition, showing potential in the application of lithium-sulfur batteries.

Liquid-Liquid and Liquid-Solid Interfacial Nanoarchitectonics

Nanoscale science is becoming increasingly important and prominent, and further development will necessitate integration with other material chemistries. In other words, it involves the construction of a methodology to build up materials based on nanoscale knowledge. This is also the beginning of the concept of post-nanotechnology. This role belongs to nanoarchitectonics, which has been rapidly developing in recent years. However, the scope of application of nanoarchitectonics is wide, and it is somewhat difficult to compile everything. Therefore, this review article will introduce the concepts of liquid and interface, which are the keywords for the organization of functional material systems in biological systems. The target interfaces are liquid-liquid interface, liquid-solid interface, and so on. Recent examples are summarized under the categories of molecular assembly, metal-organic framework and covalent organic framework, and living cell. In addition, the latest research on the liquid interfacial nanoarchitectonics of organic semiconductor film is also discussed. The final conclusive section summarizes these features and discusses the necessary components for the development of liquid interfacial nanoarchitectonics.

Assessing the Acidic and Alkaline Recalcitrance of Covalently Modified Surface Amines on Ordered Mesoporous Carbon

Ordered mesoporous carbon (OMC) scaffolds were covalently modified with primary amine groups by means of oxidation-coupling, yielding C-O-C bonds, or organometallic activation-coupling, yielding C-C bonds. The aminated OMCs were stressed by immersion in either 1 M hydrochloric acid or 1 M sodium hydroxide solutions at room temperature for 6 h and characterized by nitrogen sorption, electron microscopy, low-angle X-ray diffraction, thermogravimetric analysis, and the 4-nitrobenzaldehyde assay. Results demonstrate that aminated surfaces of OMC by butyllithium grafting are stable toward both 1 M HCl and 1 M NaOH, whereas the oxidation-aminated OMC surfaces can withstand 1 M NaOH only. This study illustrates the importance of chemical testing to supplant chemical intuition when tailoring carbon surfaces for applications where strong acids or bases are employed. This is especially emphasized for carbonaceous materials because of the surface heterogeneity among different carbon allotropes.

Morphological and structural design through hard-templating of PGM-free electrocatalysts for AEMFC applications

This study delves into the critical role of customized materials design and synthesis methods in influencing the performance of electrocatalysts for the oxygen reduction reaction (ORR) in anion exchange membrane fuel cells (AEMFCs). It introduces a novel approach to obtain platinum-free (PGM-free) electrocatalysts based on the controlled integration of iron active sites onto the surface of silica nanoparticles (NPs) by using nitrogen-based surface ligands. These NPs are used as hard templates to form tailored nanostructured electrocatalysts with an improved iron dispersion into the carbon matrix. By utilizing a wide array of analytical techniques including infrared and X-ray photoelectron spectroscopy techniques, X-ray diffraction and surface area measurements, this work provides insight into the physical parameters that are critical for ORR electrocatalysis with PGM-free electrocatalysts. The new catalysts showed a hierarchical structure containing a large portion of graphitic zones which contribute to the catalyst stability. They also had a high electrochemically active site density reaching 1.47 × 1019 sites g-1 for SAFe_M_P1AP2 and 1.14 × 1019 sites g-1 for SEFe_M_P1AP2, explaining the difference in performance in fuel cell measurements. These findings underscore the potential impact of a controlled materials design for advancing green energy applications.

Stabilizing Solid Electrolyte Interphase on Liquid Metal Via Dynamic Hydrogel-Derived Carbon Framework Encapsulation

Eutectic gallium-indium liquid metal (EGaIn-LM), with a considerable capacity and unique self-healing properties derived from its intrinsic liquid nature, gains tremendous attention for lithium-ion batteries (LIBs) anode. However, the fluidity of the LM can trigger continuous consumption of the electrolyte, and its liquid-solid transition during the lithiation/de-lithiation process may result in the rupture of the solid electrolyte interface (SEI). Herein, LM is employed as an initiator to in situ assemble the 3D hydrogel for dynamically encapsulating itself; the LM nanoparticles can be homogeneously confined within the hydrogel-derived carbon framework (HDC) after calcination. Such design effectively alleviates the volume expansion of LM and facilitates electron transportation, resulting in a superior rate capability and long-term cyclability. Further, the "dual-layer" SEI structure and its key components, including the robust LiF outer layer and corrosion-resistant and ionic conductive LiGaOx inner layer are revealed, confirming the involvement of LM in the formation of SEI, as well as the important role of carbon framework in reducing interfacial side reactions and SEI decomposition. This work provides a distinct perspective for the formation, structural evolution, and composition of SEI at the liquid/solid interface, and demonstrates an effective strategy to construct a reliable matrix for stabilizing the SEI.

Sharply expanding single-atomically dispersed Fe-N active sites through bidirectional coordination for oxygen reduction

For Fe-NC systems, high-density Fe-N sites are the basis for high-efficiency oxygen reduction reaction (ORR), and P doping can further lower the reaction energy barrier, especially in the form of metal-P bonding. However, limited to the irregular agglomeration of metal atoms at high temperatures, Fe-P bonds and high-density Fe-N cannot be guaranteed simultaneously. Here, to escape the random and violent agglomeration of Fe species during high-temperature carbonization, triphenylphosphine and 2-methylimidazole with a strong metal coordination capability are introduced together to confine Fe growth. With the aid of such bidirectional coordination, the high-density Fe-N site with Fe-P bonds is realized by in situ phosphorylation of Fe in an Fe-NC system (Fe-P-NC) at high temperatures. Impressively, the content of single-atomically dispersed Fe sites for Fe-P-NC dramatically increases from 2.8% to 65.3% compared with that of pure Fe-NC, greatly improving the ORR activity in acidic and alkaline electrolytes. The theoretical calculation results show that the generated Fe2P can simultaneously facilitate the adsorption of intermediates to Fe-N4 sites and the electron transfer, thereby reducing the reaction energy barrier and obtaining superior ORR activity.

Enhanced electrocatalytic performance for H2O2 generation by boron-doped porous carbon hollow spheres

Electrocatalytic generation of H2O2 via the 2-electron pathway of oxygen reduction reaction (2e-ORR) is an attractive technology compared to the anthraquinone process due to convenience and environmental friendliness. However, catalysts with excellent selectivity and high activity for 2e-ORR are necessary for practical applications. Reported here is a catalyst comprising boron-doped porous carbon hollow spheres (B-PCHSs) prepared using the hard template method coupled with borate transesterification. In an alkali electrolyte, the selectivity of B-PCHS for 2e-ORR above 90% in range of 0.4-0.7 VRHE and an onset potential of 0.833 V was obtained. Meanwhile, the generation rate of H2O2 reached 902.48 mmol h-1 gcat-1 at 0.4 VRHE under 59.13 mA cm-2 in batch electrolysis. The excellent catalytic selectivity of B-PCHS for 2e-ORR originates from the boron element, and the catalytic activity of B-PCHS for H2O2 generation is contributed to the morphology of porous hollow spheres, which facilitates mass transfer processes.

Volatile guest molecule mediated strategy to convert covalent organic framework into nitrogen, sulfur-doped carbon as metal-free oxygen reduction electrocatalysts

Covalent organic framework (COF) derived metal-free carbon materials have emerged as promising electrocatalysts for the oxygen reduction reaction (ORR). Herein, a volatile guest molecule mediated-pyrolysis strategy was explored on a designed thiophene-rich and imine-linked COF. Through the modulation of guest mediators (iodine and sulfur), the properties of the as-obtained carbon materials can be well regulated. The optimized nitrogen and sulfur dual-doped carbon electrocatalyst demonstrates remarkable ORR activity with a half-wave potential of 0.87 V and impressive durability, with only an 8% current loss over 21 h. The corresponding assembled zinc-air battery has a comparable power density (60 mW cm-2) to that of the commercial Pt/C. It is proposed that the coexistence of the guest mediators iodine and sulfur in the channels of COFs could prevent the loss of N species. The enhanced N content and N/S ratio are assumed to be responsible for the ORR performance. This study puts forward a novel strategy to prepare COF-derived carbon materials mediated by volatile guest molecules, which may provide new insights into the development of metal-free ORR catalysts.

Layer-by-layer designer nanoarchitectonics for physical and chemical communications in functional materials

Nanoarchitectonics, as a post-nanotechnology concept, constructs functional materials and structures using nanounits of atoms, molecules, and nanomaterials as materials. With the concept of nanoarchitectonics, asymmetric structures, and hierarchical organization, rather than mere assembly and organization of structures, can be produced, where rational physical and chemical communications will lead to the development of more advanced functional materials. Layer-by-layer assembly can be a powerful tool for this purpose, as exemplified in this feature paper. This feature article explores the possibility of constructing advanced functional systems based on recent examples of layer-by-layer assembly. We will illustrate both the development of more basic methods and more advanced nanoarchitectonics systems aiming towards practical applications. Specifically, the following sections will provide examples of (i) advancement in basics and methods, (ii) physico-chemical aspects and applications, (iii) bio-chemical aspects and applications, and (iv) bio-medical applications. It can be concluded that materials nanoarchitectonics based on layer-by-layer assembly is a useful method for assembling asymmetric structures and hierarchical organization, and is a powerful technique for developing functions through physical and chemical communication.

Acidified Nitrogen Self-Doped Porous Carbon with Superprotonic Conduction for Applications in Solid-State Proton Battery

Solid proton electrolytes play a crucial role in various electrochemical energy storage and conversion devices. However, the development of fast proton conducting solid proton electrolytes at ambient conditions remains a significant challenge. In this study, a novel acidified nitrogen self-doped porous carbon material is presented that demonstrates exceptional superprotonic conduction for applications in solid-state proton battery. The material, designated as MSA@ZIF-8-C, is synthesized through the acidification of nitrogen-doped porous carbon, specifically by integrating methanesulfonic acid (MSA) into zeolitic imidazolate framework-derived nitrogen self-doped porous carbons (ZIF-8-C). This study reveals that MSA@ZIF-8-C achieves a record-high proton conductivity beyond 10-2  S cm-1 at ambient condition, along with good long-term stability, positioning it as a cutting-edge alternative solid proton electrolyte to the default aqueous H2 SO4 electrolyte in proton batteries.

Hollow mesoporous carbon supported Co-modified Cu/Cu2O electrocatalyst for nitrate reduction reaction

The electroreduction of nitrate (NO3-) pollutants to ammonia (NH3) provides a sustainable approach for both wastewater treatment and NH3 synthesis. However, electroreduction of nitrate requires multi-step electron and proton transfer, resulting in a sluggish reaction rate. Herein, we synthesized a Co-modified Cu/Cu2O catalyst supported on hollow mesoporous carbon substrates (Co/Cu/Cu2O-MesoC) by a one-step microwave-assisted reduction method. At -0.25 V vs. reversible hydrogen electrode (RHE), Co/Cu/Cu2O-MesoC shows a Faradaic efficiency (FE) of 100 ± 1% in 0.1 M NO3-. Notably, the maximum NH3 yield rate (YieldNH3) reaches 6.416 ± 0.78 mmol mgcat-1h-1 at -0.45 V vs. RHE, which is much better than most of the previous reports. Electrochemical evaluation and in-situ Fourier transform infrared (FTIR) spectroscopy reveal that the addition of Co could promote water electrolysis, and the generated H* is involved in the following hydrogenation of intermediates, ultimately leading to faster kinetics and energetics during electrocatalytic conversion of NO3- to NH3. This synergetic electrocatalysis strategy opens a new avenue for the development of high-activity, selectivity, and stability catalysts.

Encapsulation of Co nanoparticles with single-atomic Co sites into nitrogen-doped carbon for electrosynthesis of hydrogen peroxide

The electrosynthesis of hydrogen peroxide (H2O2) offers a sustainable and viable option for generating H2O2 directly, as an alternative to the anthraquinone oxidation method. This study focuses on the comparative study of Co nanoparticles and single-atomic Co sites (Co SACs) that were encapsulated into nitrogen-doped carbon for the electrosynthesis of H2O2, which has been synthesized by direct pyrolysis of Zn/Co-ZIF or Co-based zeolitic imidazolate frameworks (ZIF-67). The electrochemical measurement results demonstrate that the coexistence of Co nanoparticles and single-atomic Co sites in the CoNC catalyst is more conducive for H2O2 production compared to Co SACs only, possessing better H2O2 selectivity of 73.3% and higher faradaic efficiency of 87%. The improved performance of CoNC with SACs can be attributed to the presence of additional Co nanoparticles in the nitrogen-doped carbon layers.

Mesoporous dopamine-modified leaf-like zeolitic imidazolate frameworks derived carbon for efficient capacitive deionization

The onstruction of novel porous carbon materials for efficient desalination is crucial but remains challenging for capacitive deionization (CDI) development. Herein, a micelle-assisted strategy was raised to coat mesoporous polydopamine (mPDA) on the surface of two-dimensional (2D) leaf-like zeolitic imidazolate frameworks (ZIFL) followed by confinement pyrolysis. The introduction of the mPDA layer can not only mitigate the backbone collapse of ZIFL during pyrolysis to build a favorable porous environment for efficient ion transport and diffusion, but also induce explosive growth of carbon nanotubes (CNTs) to improve the electron conductivity. As expected, the derivative ZIFL@mPDA-C possessed a high desalination capacity of 41.9 mg g-1 in 500  mg L-1 NaCl solution at an operating voltage of 1.2 V. In particular, the retention ratio of the desalination capacity of ZIFL@mPDA-C was about 100 % after 50 consecutive adsorption-desorption cycles, while its leaf-like morphology and hierarchical pore structures were well preserved. This study highlights the importance of rationally designed structures and components for the performance breakthrough of carbon-based CDI electrode materials.

Enhancing Electrocatalytic Performance via Thickness-Tuned Hollow N-Doped Mesoporous Carbon with Embedded Co Nanoparticles for Oxygen Reduction Reaction

Improving catalytic performance relies heavily on the rational design of the spatial structure of electrocatalysts, achieved through exposure of active sites, acceleration of the charge/mass transfer rate, and confinement of the reactants. In this study, we have fabricated Co nanoparticles embedded in overhang eave-like hollow N-doped mesoporous carbon (Co@EMPC) by adjusting the thickness of mesoporous polydopamine (mPDA). Thanks to the abundance of short mesoporous channels within the porous structure and the tuned electronic properties resulting from heterojunction structures between metal and carbon, the prepared Co@EMPC provides increased accessibility to active sites and enhanced mass and charge transfer rates. These features contribute to superior performance in the oxygen reduction reaction (ORR), with a half-wave potential of 0.874 V vs RHE, as well as exceptional durability in alkaline media. This study introduces a useful approach to enhance the ORR using eave-like hollow nanoreactors.

Solvent-pair surfactants enabled assembly of clusters and copolymers towards programmed mesoporous metal oxides

Organic-inorganic molecular assembly has led to numerous nano/mesostructured materials with fantastic properties, but it is dependent on and limited to the direct interaction between host organic structure-directing molecules and guest inorganic species. Here, we report a "solvent-pair surfactants" enabled assembly (SPEA) method to achieve a general synthesis of mesostructured materials requiring no direct host-guest interaction. Taking the synthesis of mesoporous metal oxides as an example, the dimethylformamide/water solvent pairs behave as surfactants and induce the formation of mesostructured polyoxometalates/copolymers nanocomposites, which can be converted into metal oxides. This SPEA method enables the synthesis of functional ordered mesoporous metal oxides with different pore sizes, structures, compositions and tailored pore-wall microenvironments that are difficult to access via conventional direct organic-inorganic assembly. Typically, nitrogen-doped mesoporous ε-WO3 with high specific surface area, uniform mesopores and stable framework is obtained and exhibits great application potentials such as gas sensing.

V-O Species-Doped Carbon Frameworks Loaded with Ru Nanoparticles as Highly Efficient and CO-Tolerant Catalysts for Alkaline Hydrogen Oxidation

Efficient and CO-tolerant catalysts for alkaline hydrogen oxidation (HOR) are vital to the commercial application of anion exchange membrane fuel cells (AEMFCs). Herein, a robust Ru-based catalyst (Ru/VOC) with ultrasmall Ru nanoparticles supported on carbon frameworks with atomically dispersed V-O species is prepared elaborately. The catalyst exhibits a remarkable mass activity of 3.44 mA μgPGM, which is 31.3 times that of Ru/C and even 4.7 times higher than that of Pt/C. Moreover, the Ru/VOC anode can achieve a peak power density (PPD) of 1.194 W cm-2, much superior to that of Ru/C anode and even better than that of Pt/C anode. In addition, the catalyst also exhibits superior stability and exceptional CO tolerance. Experimental results and density functional theory (DFT) calculations demonstrate that V-O species are ideal OH- adsorption sites, which allow Ru to release more sites for hydrogen adsorption. Furthermore, the electron transfer from Ru nanoparticles to the carbon substrate regulates the electronic structure of Ru, reducing the hydrogen binding energy (HBE) and the CO adsorption energy on Ru, thus boosting the alkaline HOR performance and CO tolerance of the catalyst. This is the first report that oxophilic single atoms distributed on carbon frameworks serve as OH- adsorption sites for efficient hydrogen oxidation, opening up new guidance for the elaborate design of high-activity catalysts for the alkaline HOR.

Aromatic biomass (torch ginger) leaf-derived three-dimensional honeycomb-like carbon to enhance gravimetric supercapacitor

BACKGROUND

Porous carbon electrode (PCE) is identified as a highly suitable electrode material for commercial application due to its production process, which is characterized by simplicity, cost-effectiveness and environmental friendliness. PCE was synthesized using torch ginger (Etlingera elatior (Jack) R.M. Smith) leaves as the base material. The leaves were treated with different concentrations of ZnCl2 , resulting in a supercapacitor cell electrode with unique honeycomb-like three-dimensional (3D) morphological pore structure. This PCE comprises nanofibers from lignin content and volatile compounds from aromatic biomass waste.

RESULTS

From the characterization of physical properties, PCE-0.3 had an impressive amorphous porosity, wettability and 3D honeycomb-like structural morphology with a pore framework consisting of micropores and mesopores. According to the structural advantages of 3D hierarchical pores such as interconnected honeycombs, PCE-0.3 as supercapacitor electrode had a high specific capacitance of up to 285.89 F g-1 at 1 A. Furthermore, the supercapacitor exhibited high energy and power density of 21.54 Wh kg-1 and 161.13 W kg-1 , respectively, with a low internal resistance of 0.059 Ω.

CONCLUSION

The results indicated that 3D porous carbon materials such as interconnected honeycombs derived from the aromatic biomass of torch ginger leaves have significant potential for the development of sustainable energy storage devices. © 2023 Society of Chemical Industry.

Unlocking Catalytic Potential: Encasing CoP Nanoparticles within Mesoporous CoFeP Nanocubes for Enhanced Oxygen Evolution Reaction

Efficient and durable electrocatalysts fabricated by using nanosized nonprecious-metal-based materials have attracted considerable attention for use in the oxygen evolution reaction (OER). Understanding performance disparities and structure-property relationships of various nonprecious-metal-based nanostructures is crucial for optimizing their applications. Herein, CoP nanoparticles encompassed within a CoFeP shell (named CoP/CoFeP) are fabricated. The mesoporous CoFeP shell enables effective mass transport, affords abundant active sites, and ensures the accessibility of hybrid interfaces between CoP and CoFeP. Therefore, encased CoP/CoFeP nanocubes exhibit excellent OER catalytic activity with an overpotential of 266 mV at a current density of 10 mA cm-2 in alkaline media, superior to reference hollow CoFeP nanocubes and commercial RuO2. Experimental characterization and theoretical calculations show that the encased structure of CoP/CoFeP with a rich Fe-doped shell enables electronic interactions between CoP and CoFeP, as well as accelerates structural reconstruction that exposes more active sites, yielding an enhanced OER performance. This study aims to inspire further work on nonprecious-metal catalysts with tailored nanostructures and electronic properties for the OER.

Hollow spherical Mn0.5Zn0.5Fe2O4 nanoparticles with a magnetic vortex configuration for enhanced magnetic hyperthermia efficacy

Conventional magnetic nanoagents in cancer hyperthermia therapy suffer from a low magnetic heating efficiency. To address this issue, researchers have pursued magnetic nanoparticles with topological magnetic domain structures, such as the vortex-domain structure, to enhance the magnetic heating performance of conventional nanoparticles while maintaining excellent biocompatibility. In this study, we synthesized hollow spherical Mn0.5Zn0.5Fe2O4 (MZF-HS) nanoparticles using a straightforward solvothermal method, yielding samples with an average outer diameter of approximately 350 nm and an average inner diameter of about 220 nm. The heating efficiency of the nanoparticles was experimentally verified, and the specific absorption rate (SAR) value of the hollow MZF was found to be approximately 1.5 times that of solid MZF. The enhanced heating performance is attributed to the vortex states in the hollow MZF structure as validated with micromagnetic simulation studies. In vitro studies demonstrated the lower cell viability of breast cancer cells (MCF-7, BT549, and 4T1) after MHT in the presence of MZF-HS. The synthesized MZF caused 51% cell death after MHT, while samples of MZF-HS resulted in 77% cell death. Our findings reveal that magnetic particles with a vortex state demonstrate superior heating efficiency, highlighting the potential of hollow spherical particles as effective heat generators for MHT applications.

Nanostructure engineering of Pt/Pd-based oxygen reduction reaction electrocatalysts

Increasing the atomic utilization of Pt and Pd elements is the key to the advancement and broad dissemination of fuel cells. Central to this task is the design and fabrication of highly active and stable Pt- or Pd-based electrocatalysts for the oxygen reduction reaction (ORR), which requires a comprehensive understanding of the ORR pathways and mechanism. Past endeavors have accumulated a wealth of knowledge about the Pt/Pd-based ORR electrocatalysts based on structure engineering, while a systematic review of the nanostructure engineering of Pt/Pd-based ORR electrocatalysts has been rarely reported. In this review, we provide a systematic discussion about the current status of Pt/Pd-based ORR electrocatalysts from the perspective of nanostructure engineering, and we highlight the ORR pathways, mechanisms and theories in order to understand the ORR in a more complex nanocatalyst. Particularly, the underlying structure-function relationship of Pt/Pd-based ORR electrocatalysts is specifically highlighted, which will guide the future synthesis of more efficient ORR electrocatalysts.

Fe-Co Bimetallic Catalysts for Pyrolysis of Disposable Face Masks and Nitrile Gloves: Synthesis and Characterization of N-Doped Carbon Nanotubes

The global spread of severe acute respiratory syndrome coronavirus 2 has led to a widespread surge in the use of disposable medical face masks (DFMs) and waste nitrile gloves (WNGs). To address the immense disruption in waste management systems, the catalytic pyrolysis of DFMs and WNGs was undertaken to yield multiwalled carbon nanotubes. Two MgO-supported bimetallic catalysts, Fe-Co and Fe-Ni, were synthesized for catalytic pyrolysis. The MgO-supported Fe and Co catalysts showed a good yield of N-doped CNTs (N-CNTs) above 33 wt %, while the percentage of WNGs did not exceed 20 wt %. The pyrolysis process resulted in the formation of Fe-Co microspinels, which were subsequently encapsulated within N-CNTs, ultimately yielding FeCo-NCNTs. The synthesized FeCo-NCNTs were approximately 25 nm in diameter and were extended over several micrometers in length. Subsequent evaluations included testing several acid-washed FeCo-NCNTs as catalysts for the oxygen reduction reaction. The FeCo-NCNTs exhibited remarkable catalytic performance, with a half-wave potential at 0.831 V (vs RHE) and exceptional resistance to methanol poisoning. These remarkable findings have the potential to contribute to the sustainable recycling of waste generated during the COVID-19 pandemic and to the utilization of waste-derived materials.

Open-Mouthed Hollow Carbons: Systematic Studies as Cobalt- and Nitrogen-Doped Carbon Electrocatalysts for Oxygen Reduction Reaction

Although hollow carbon structures have been extensively studied in recent years, their interior surfaces are not fully utilized due to the lack of fluent porous channels in the closed shell walls. This study presents a tailored design of open-mouthed particles hollow cobalt/nitrogen-doped carbon with mesoporous shells (OMH-Co/NC), which exhibits sufficient accessibility and electroactivity on both the inner and outer surfaces. By leveraging the self-conglobation effect of metal sulfate in methanol, a raspberry-structured Zn/Co-ZIF (R-Zn/Co-ZIF) precursor is obtained, which is further carbonized to fabricate the OMH-Co/NC. In-depth electrochemical investigations demonstrate that the introduction of open pores can enhance mass transfer and improve the utilization of the inner active sites. Benefiting from its unique structure, the resulting OMH-Co/NC exhibits exceptional electrocatalytic oxygen reduction performance, achieving a half-wave potential of 0.865 V and demonstrating excellent durability.

Carbon Nitride Coupled Co3O4: A Pyrolysis-Based Approach for High-Performance Hybrid Energy Storage

Graphitic carbon nitride (CN) is a cost-effective and easily synthesized supercapacitor electrode material. However, its limited specific capacity has hindered its practical use. To address this, we developed a binary nanostructure by growing nanosized Co3O4 particles on CN. The CN-Co-2 composite, synthesized via thermal decomposition, exhibited a remarkable specific capacity of 280.64 C/g at 2 A/g. Even under prolonged cycling at 10.5 A/g, the retention rate exceeded 95%, demonstrating exceptional stability. In an asymmetric capacitor device, the CN-Co composite delivered 20.84 Wh/kg at 1000 W/kg, with a retention rate of 99.97% over 20,000 cycles, showcasing outstanding cycling stability. Controlled cobalt source adjustments yielded high-capacity electrode materials with battery-like behavior. This optimization strategy enhances energy density by retaining battery-like properties. In summary, the CN-Co composite is a promising, low-cost, easily synthesized electrode material with a high specific capacity and remarkable cycling stability, making it an attractive choice for energy storage applications.

Enhancing the bifunctional oxygen reduction and evolution activity of CoNC by introducing a trace amount of Fe

The potential application of zinc air batteries to tackle the energy shortage and environmental crisis has proposed new requirements of bifunctional catalysts for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Utilizing the special spatial structure of zeolitic imidazolate framework-67 (ZIF-67) as an ideal research platform, the effect of a trace amount of Fe on the composition and structure of as-obtained Fe-CoNC catalysts was investigated. It was revealed that, due to the increased exposed pore structure and metal species located at the near surface, the active sites for the ORR/OER on Fe-CoNC are highly exposed, greatly boosting the activity to the reduction and evolution of oxygen in alkaline media. ZABs with Fe-CoNC have the highest maximum power density of 200 mW cm-2 when operated at current densities as high as 328 mA cm-2, better than not only Fe-free CoNC, but also precious metal-based references with the same catalyst loading.

Built-in Electric Field-Induced Work Function Reduction in C-Co3O4 for Efficient Electrochemical Nitrogen Reduction

Co3O4 is a highly selective catalyst for the electrochemical conversion of N2 to NH3. However, the large work function (WF) of Co3O4 leads to unsatisfactory activity. To address this issue, a strong built-in electric field (BIEF) was constructed in Co3O4 by doping C atoms (C-Co3O4) to reduce the WF for improving the electrocatalytic performance. C-Co3O4 exhibited a remarkable NH3 yield of 38.5 μg h-1 mgcat-1 and a promoted FE of 15.1% at -0.3 V vs RHE, which were 2.2 and 1.9 times higher than those of pure Co3O4, respectively. Kelvin probe force microscopy (KPFM), zeta potential, and ultraviolet photoelectron spectrometry (UPS) confirmed the formation of strong BIEF and WF reduction in C-Co3O4. Additionally, in situ Raman measurements and density functional theory (DFT) calculations revealed the relationship between BIEF and WF and provided insights into the reaction mechanism. Our work offers valuable guidance for the design and development of more efficient nitrogen reduction catalysts.

A Ni-doped Mo2C/NCF composite for efficient electrocatalytic hydrogen evolution

Ni-Mo₂C nano catalysts dispersed on N-doped carbon flowers: a composite with nitrogen-containing carbon flowers carrying nickel-modified molybdenum carbide exhibits enhanced HER catalytic activity in alkaline electrolyte.

Nonacid Carbon Materials as Catalysts for Monoethanolamine Energy-Efficient Regeneration

In the CO₂ capture process, solid acid catalysts have been widely adopted to decrease energy consumption in the amine regeneration process owing to abundant acid sites. However, acid sites unavoidably degenerate in the basic amine solution. To address the challenge, nonacid carbon materials including carbon molecular sieves, porous carbon, carbon nanotubes, and graphene are first proposed to catalyze amine regeneration. It is found that carbon materials can significantly increase the CO₂ desorption amount by 47.1-72.3% and reduce energy consumption by 32-42%. In 20 stability experiments, CO₂ loading was stable with the max difference value of 0.01 mol CO₂/mol monoethanolamine (MEA), and no obvious increase in the relative heat duty (the maximum difference is 4%) occurred. The stability of carbon materials is superior to excellent solid acid catalysts, and the desorption performance is comparable. According to the results of theoretical calculation and experimental characterization, the electron-transfer mechanism of nonacid carbon materials is proposed, which is not only beneficial for MEA regeneration but also the probable reason for the stable catalytic activity. Owing to the excellent catalytic performance of carbon nanotube (CNT) in the HCO₃^- decomposition, nonacid carbon materials are quite promising to enhance the desorption performance of novel blend amines, which will further reduce the cost of carbon capture in the industry. This study provides a new strategy to develop stable catalysts used for amine energy-efficient regeneration.

Iron Nanoparticles Wrapped with an N-Doped Carbon Material Produced by Using a Zinc Hydroxide Ferrocyanide Nanohybrid for Use in Commercial-like Supercapacitors

According to the technology of carbon-based supercapacitors, modifying the structure of carbon as an active electrode material leads to an increase in capacitance. A modification involves introducing heteroatoms such as nitrogen into the carbon structure and composing it with metals such as iron. In this research, an anionic source called ferrocyanide was used to produce N-doped carbon consisting of iron nanoparticles. In fact, ferrocyanide was located as a guest between the layers of a host material, which is zinc hydroxide in the α phase. This new nanohybrid material was then heat-treated under Ar, and the heated product after acid washing was iron nanoparticles wrapped with N-doped carbon materials. This material was used as an active material in the production of symmetric supercapacitors with different organic (TEABF₄ in acetonitrile) and aqueous (sodium sulfate) electrolytes as well as a new electrolyte (KCN in methanol). Accordingly, the supercapacitor made by the N/Fe-carbon active material and the organic electrolyte showed a capacitance value of 21 F/g at a current density of 0.1 A/g. This value is comparable to and even higher than the values observed in commercial supercapacitors.

Hierarchical porous Fe-N/C@surfactant composites synthesized by a surfactant-assisted strategy as high-performance bifunctional oxygen electrodes for rechargeable zinc-air batteries

Herein, a soft-template strategy involving the cationic surfactants has been successfully applied to size-controlled synthesis of hierarchical porous Fe-N/C for the first time. Specifically, a small amount of Fe and cationic surfactants can be uniformly doped into the zinc-based zeolite imidazole framework (ZIF-8) crystal particles and the cationic surfactants play a critical role in the formation of hierarchically porous Fe-ZIF-8@surfactant precursors. When the Fe-ZIF-8@surfactant is subsequently pyrolyzed, atomically dispersed Fe-N_x coordination structures can be in-situ converted to Fe-N/C, while the cationic surfactants decompose to form a carbon matrix to encapsulate the active sites, thereby preventing the aggregation of nanoparticles to a certain extent. As a result, the combined Fe nanocrystals and atomically dispersed Fe-N_x in the graphitic carbon matrix generate a synergistic effect to boost the electrocatalytic behaviors with a more positive half-wave potential (0.92 V) for oxygen reduction reaction (ORR) and a lower overpotential (420 mV at 10 mA cm^-2) for oxygen evolution reaction (OER). As a proof of concept, the Fe-N/C@TTAB based zinc-air batteries (ZABs) present an outstanding peak power density (107.9 mW cm^-2) and a superior specific capacity (706.3 mAh g^-1) with robust cycling stability over 900 cycles for 150 h, which are better than the commercial Pt/C + IrO₂ based ZABs.

Space-Confined Metal Ion Strategy for Carbon Materials Derived from Cobalt Benzimidazole Frameworks with High Desalination Performance in Simulated Seawater

Various metal ions with different valence states (Mg²⁺ , Al³⁺ , Ca²⁺ , Ti⁴⁺ , Mn²⁺ , Fe³⁺ , Ni²⁺ , Zn²⁺ , Pb²⁺ , Ba²⁺ , Ce⁴⁺ ) are successfully confined in quasi-microcube shaped cobalt benzimidazole frameworks using a space-confined synthesis strategy. More importantly, a series of derived carbon materials that confine metal ions are obtained by high-temperature pyrolysis. Interestingly, the derived carbon materials exhibited electric double-layer and pseudocapacitance properties because of the presence of metal ions with various valence states. Moreover, the presence of additional metal ions within carbon materials may create new phases, which can accelerate Na⁺ insertion/extraction and thus increase electrochemical adsorption. Density functional theory results showed that carbon materials in which Ti ions are confined exhibit enhanced insertion/extraction of Na⁺ resulting from the presence of the characteristic anatase crystalline phases of TiO₂ . The Ti-containing materials have an impressive desalination capacity (62.8 mg g^-1 ) in capacitive deionization (CDI) applications with high cycling stability. This work provides a facile synthetic strategy for the confinement of metal ions in metal-organic frameworks and thus supports the further development of derived carbon materials for seawater desalination by CDI.

Critical role of Photo-electrode with Ce-g-C3N4 in multi-stage microbial fuel cells cascade reactor treating diluted hyper-saline industrial wastewater rich in amines

Treatment of chemical industrial wastewater often faces problems of large volume occupation, high cost, and long processing time. In this study, low-content Ce-modified g-C₃N₄ was prepared and used as a catalyst on stainless steel mesh photo-cathode in constructing a multi-stage cascade microbial fuel cell system to reduce treatment costs in an energy-saving way. The large specific surface area (332.5 m² g^-1) and mesoporous structure of the material, is favorable for catalytic reactions, in which Ce elements were mainly present in single atoms. The characterized catalyst indicated a pronounced effect of Ce species in increasing photo-current and the synergistic pollutant removal, microbial bio-degradation and cascade operation stability. In Batch-mode (light illumination, aeration, total HRT (hydraulic residence time) of 54 h) treatment through three cascade reactors, removed 88% COD (Chemical Oxygen Demand). With 0.5 mM PMS (peroxymonosulfate), 94% COD and 86% NH₄⁺-N of the system were removed. The cascade net average COD removal capacity reached 16.04 kg per kg catalyst per day. The addition of PMS also enhanced the electricity generation. In continuous-mode, in totally 18 h treatment through the three-stages cascade reactors without PMS, overall, 83% COD and 78% TOC (Total Organic Carbon) were removed, reaching a net calculated system average COD removal capacity of 19.29 kg per kg catalyst per day. With Ce-g-C₃N₄ catalyst, the batch or continuous multi-stage cascade system demonstrated great technical flexibility and economic potential in treating high-strength, high-salinity amine-rich industrial wastewater.

CoMoO4-CoP/NC heterostructure anchored on hollow polyhedral N-doped carbon skeleton for efficient water splitting

We report the synthesis and electrocatalytic properties of a CoMoO₄-CoP heterostructure anchored on a hollow polyhedral N-doped carbon skeleton (CoMoO₄-CoP/NC) for water-splitting applications. The preparation involved the anion exchange of MoO₄^2- to the organic ligand of ZIF-67, the self-hydrolysis of MoO₄^2-, and NaH₂PO₂ phosphating annealing. CoMoO₄ was found to enhance thermal stability and prevent active site agglomeration during annealing, while the hollow structure of CoMoO₄-CoP/NC provided a large specific surface area and high porosity that facilitated mass transport and charge transfer. The interfacial electron transfer from Co to Mo and P sites promoted the generation of electron-deficient Co sites and electron-enriched P sites, which accelerated water dissociation. CoMoO₄-CoP/NC exhibited excellent electrocatalytic activity for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in 1.0 M KOH solution, with overpotentials of 122 mV and 280 mV at 10 mA cm^-2, respectively. The CoMoO₄-CoP/NC‖CoMoO₄-CoP/NC two-electrode system only required an overall water splitting (OWS) cell voltage of 1.62 V to achieve 10 mA cm^-2 in an alkaline electrolytic cell. In addition, the material showed comparable activity to 20% Pt/C‖RuO₂ in a pure water home-made membrane electrode device, demonstrating potential for practical applications in proton exchange membrane (PEM) electrolyzers. Our results suggest that CoMoO₄-CoP/NC is a promising electrocatalyst for efficient and cost-effective water splitting.

Synergistic effect of intercalation and EDLC electrosorption of 2D/3D interconnected architectures to boost capacitive deionization for water desalination via MoSe2/mesoporous carbon hollow spheres

Transition-metal dichalcogenides can be used for capacitive deionization (CDI) via pseudocapacitive ion intercalation/de-intercalation due to their unique two-dimensional (2D) laminar structure. MoS₂ has been extensively studied in the hybrid capacitive deionization (HCDI), but the desalination performance of MoS₂-based electrodes remains only 20-35 mg g^-1 on average. Benefiting from the higher conductivity and larger layer spacing of MoSe₂ than MoS₂, it is expected that MoSe₂ would exhibit a superior HCDI desalination performance. Herein, for the first time, we explored the use of MoSe₂ in HCDI and synthesized a novel MoSe₂/MCHS composite material by utilizing mesoporous carbon hollow spheres (MCHS) as the growth substrate to inhibit the aggregation and improve the conductivity of MoSe₂. The as-obtained MoSe₂/MCHS presented unique 2D/3D interconnected architectures, allowing for synergistic effects of intercalation pseudocapacitance and electrical double layer capacitance (EDLC). An excellent salt adsorption capacity of 45.25 mg g^- 1 and a high salt removal rate of 7.75 mg g^- 1 min^-1 were achieved in 500 mg L^- 1 NaCl feed solution at an applied voltage of 1.2 V in batch-mode tests. Moreover, the MoSe₂/MCHS electrode exhibited outstanding cycling performance and low energy consumption, making it suitable for practical applications. This work demonstrates the promising application of selenides in CDI and provides new insights for ration design of high-performance composite electrode materials.

Carbon-Based Stimuli-Responsive Nanomaterials: Classification and Application

Carbon-based nanomaterials, including carbon nanotubes, carbon nanospheres, and carbon nanofibers, are becoming a research hotspot due to their unique structure and good mechanical, thermal, electrical, optical, and chemical properties. With the development of material synthesis technology, they can be functionalized and used in various fields such as energy, environment, and biomedicine. In particular, stimuli-responsive carbon-based nanomaterials have stood out in recent years because of their smart behavior. Researchers have applied carbon-based nanomaterials to different disease treatments based on their stimulus-response properties. In this paper, based on stimuli-responsive carbon-based nanomaterials' morphology, we categorize them into carbon nanotubes, carbon nanospheres, and carbon nanofibers according to their morphology. Then, their applications in probes, bioimaging, tumor therapy, and other fields are discussed. Finally, we address the advantages and disadvantages of carbon-based stimuli-responsive nanomaterials and discuss their future perspective.

Molecular nanoarchitectonics: unification of nanotechnology and molecular/materials science

The development of nanotechnology has provided an opportunity to integrate a wide range of phenomena and disciplines from the atomic scale, the molecular scale, and the nanoscale into materials. Nanoarchitectonics as a post-nanotechnology concept is a methodology for developing functional material systems using units such as atoms, molecules, and nanomaterials. Especially, molecular nanoarchitectonics has been strongly promoted recently by incorporating nanotechnological methods into organic synthesis. Examples of research that have attracted attention include the direct observation of organic synthesis processes at the molecular level with high resolution, and the control of organic syntheses with probe microscope tips. These can also be considered as starting points for nanoarchitectonics. In this review, these examples of molecular nanoarchitectonics are introduced, and future prospects of nanoarchitectonics are discussed. The fusion of basic science and the application of practical functional materials will complete materials chemistry for everything.

Highly Efficient Electrochemical Sensing of Acetaminophen by Cobalt Oxide-Embedded Nitrogen-Doped Hollow Carbon Spheres

With respect to sensor application investigations, hollow mesoporous carbon sphere-based materials of the spinel type of cobalt oxide (Co₃O₄) and heteroatom-doped materials are gaining popularity. In this contribution, dopamine hydrochloride (DA) and cobalt phthalocyanine (CoPc) precursors were employed to construct a highly homogeneous Co₃O₄-embedded N-doped hollow carbon sphere (Co₃O₄@NHCS) by a straightforward one-step polymerization procedure. The resulting Co₃O₄@NHCS materials may effectively tune the surface area, defect sites, and doping amount of N and Co elements by altering the loading amount of CoPc. The relatively high surface area, greater spherical wall thickness, enriched defect sites, and better extent of N and Co sites are all visible in the best 200 mg loaded Co₃O₄@NHCS-2 material. This leads to significant improvement in pyridine and graphitic N site concentrations, which offers exceptional electrochemical performance. Electrochemical analysis was used to study the electrocatalytic activity of Co₃O₄@NHCSs towards the sensing of pharmacologically active significant compounds (acetaminophen). Excellent sensor properties include the linear range (0.001-0.2 and 1.0-8.0 mM), sensitivity, limit of detection (0.07 and 0.11 μM), and selectivity in the modified Co₃O₄@NHCSs/GCE. The authentic sample (acetaminophen tablet) produces a satisfactory result when used practically.

Growth Control of Metal-Organic Framework Films on Marine Biological Carbon and Their Potential-Dependent Dopamine Sensing

Ever-evolving advancements in films have fueled many of the developments in the field of electrochemical sensors. For biosensor application platforms, the fabrication of metal-organic framework (MOF) films on microscopically structured substrates is of tremendous importance. However, fabrication of MOF film-based electrodes always exhibits unsatisfactory performance, and the mechanisms of the fabrication and sensing application of the corresponding composites also need to be explored. Here, we report the fabrication of conformal MIL-53 (Fe) films on carbonized natural seaweed with the assistance of an oxide nanomembrane and a potential-dependent electrochemical dopamine (DA) sensor. The geometry and structure of the composite can be conveniently tuned by the experimental parameters, while the sensing performance is significantly influenced by the applied potential. The obtained sensor demonstrates ultrahigh sensitivity, a wide linear range, a low limit of detection, and a good distinction between DA and ascorbic acid at an optimized potential of 0.3 V. The underneath mechanism is investigated in detail with the help of theoretical calculations. This work bridges the natural material and MOF films and is promising for future biosensing applications.

Volcano relationships and a new activity descriptor of 2D transition metal-Fe layered double hydroxides for efficient oxygen evolution reaction

Iron (Fe) sites play a critical role in boosting the catalytic activity of transition metal layered double hydroxide (LDH) electrocatalysts for the oxygen evolution reaction (OER), but the contribution of the Fe content to the catalysis of Fe-doped LDHs is still not well understood. Herein, a series of two-dimensional (2D) Fe-doped MFe-LDHs (M = Co, Ni, Cu, and Mn) was synthesized via a general molecular self-assembly method to track the role of Fe in their electrocatalytic OER activities. Besides the revelation of the intrinsic activity trend of NiFe > CoFe > MnFe > CuFe, volcano-shaped relationships among the catalytic activity descriptors, i.e., overpotential, Tafel slope, and turnover frequency (TOF), and the Fe-content in MFe-LDHs, were identified. Specifically, a ∼20% Fe content resulted in the highest OER performance for the LDH, while excess Fe compromised its activity. A similar volcano relationship was determined between the intermediate adsorption and Fe content via operando impedance spectroscopy (EIS) measurements, and it was shown that the intermediate adsorption capacitance (CPE_ad) can be a new activity descriptor for electrocatalysts. In this work, we not only performed a systematic study on the role of Fe in 2D Fe-doped LDHs but also offer some new insights into the activity descriptors for electrocatalysts.

A novel approach to pulsed laser deposition of platinum catalyst on carbon particles for use in polymer electrolyte membrane fuel cells

The research undertaken aimed to develop an efficient Pt-based catalyst for polymer electrolyte membrane fuel cells (PEMFCs) by using a cost-effective and efficient physical method to deposit platinum nanoparticles (PtNPs) on carbon supports directly from the platinum target. The method developed avoids the chemical functionalization of the carbon substrate and the chemical synthesis of PtNPs during catalyst fabrication. Platinum was deposited on carbon particles at room temperature using a pulsed laser deposition (PLD) system equipped with an ArF excimer laser (λ = 193 nm). The uniform deposition of PtNPs on carbon supports was achieved thanks to a specially designed electromechanical system that mixed the carbon support particles during platinum deposition. In the studies, Vulcan XC-72R carbon black powder, a popular material used as support in the anodes and cathodes of PEMFCs, and a porous carbon material with a high degree of graphitization were used as carbon supports. The best electrochemical measurement results were obtained for Pt deposited on Vulcan XC-72R. The peak power density measured for this material in a membrane electrode assembly (MEA) of a PEMFC (fed with H₂/Air) was 0.41 W/cm², which is a good result compared to 0.57 W/cm² obtained for commercial 20% Pt Vulcan XC-72R. This result was achieved with three times less Pt catalyst on the carbon support compared to the commercial catalyst, which means that a higher catalyst utilization factor was achieved.

Explosion Strategy Engineering Oxygen-Functionalized Groups and Enlarged Interlayer Spacing of the Carbon Anode for Enhanced Lithium Storage

Amorphous carbon monoliths with tunable microstructures are candidate anodes for future lithium-based energy storage. Enhancing lithium storage capability and solid-state diffusion kinetics are the precondition for practical applications. Transforming intrinsic oxygen-rich defects into active sites and engineering enlarged interlayer spacing are of great importance. Herein, a novel explosion strategy is designed based on oxalate pyrolysis producing CO and CO₂ to successfully prepare lignin-derived carbon monolith (LSCM) with active carbonyl (C═O) groups and enlarged interlayer spacing. Explosion promotes the demethylation of methoxyl groups and cleavage of carboxyl groups to form C═O groups. CO₂ etches carbon atoms in a short time to improve the heteroatom level, expanding the interlayer spacing. ZnC₂O₄ is decomposed at 400 °C, simultaneously producing CO and CO₂, which constructs less C═O groups and large interlayer spacing. MgC₂O₄ is decomposed at 450 and 480 °C, staged-weakly producing CO and CO₂, which constructs more C═O groups and larger interlayer spacing. CaC₂O₄ is decomposed at 480 and 700 °C, staged-uniformly producing CO and CO₂, which constructs abundant C═O groups and largest interlayer spacing. The LSCM prepared by staged-uniform explosion exhibits high lithium storage capacity, superior rate capability, and cycling performance. The assembled lithium ion capacitor device achieves excellent energy/power densities of 78 Wh kg^-1/100 W kg^-1 and superior durability (capacitance retention of 8 4.6% after 20,000 cycles). This work gives a novel insight to engineer advanced oxygen-functionalized carbons for enhanced lithium storage.

Biomass Nanoarchitectonics for Supercapacitor Applications

Nanoarchitectonics integrates nanotechnology with numerous scientific disciplines to create innovative and novel functional materials from nano-units (atoms, molecules, and nanomaterials). The objective of nanoarchitectonics concept is to develop functional materials and systems with rationally architected functional units. This paper explores the progress and potential of this field using biomass nanoarchitectonics for supercapacitor applications as examples of energetic materials and devices. Strategic design of nanoporous carbons that exhibit ultra-high surface area and hierarchically pore architectures comprising micro- and mesopore structure and controlled pore size distributions are of great significance in energy-related applications, including in high-performance supercapacitors, lithium-ion batteries, and fuel cells. Agricultural wastes or natural biomass are lignocellulosic materials and are excellent carbon sources for the preparation of hierarchically porous carbons with an ultra-high surface area that are attractive materials in high-performance supercapacitor applications due to high electrical and ion conduction, extreme porosity, and exceptional chemical and thermal stability. In this review, we will focus on the latest advancements in the fabrication of hierarchical porous carbon materials from different biomass by chemical activation method. Particularly, the importance of biomass-derived ultra-high surface area porous carbons, hierarchical architectures with interconnected pores in high-energy storage, and high-performance supercapacitors applications will be discussed. Finally, the current challenges and outlook for the further improvement of carbon materials derived from biomass or agricultural wastes in the advancements of supercapacitor devices will be discussed.

Advances in Biosensing of Chemical Food Contaminants Based on the MOFs-Graphene Nanohybrids

Food safety issue is becoming an international challenge for human health owing to the presence of contaminants. In this context, reliable, rapid, and sensitive detecting technology is extremely demanded to establish food safety assurance systems. MOFs (Metal-organic frameworks) are a new type of porous crystalline material with particular physical and chemical characteristics presented in food safety requirements. (Bio)sensors driven MOF materials have emerged as a promising alternative and complementary analytical techniques, owing to their great specific area, high porosity, and uniform and fine-tunable pore buildings. Nevertheless, the insufficient stability and electrical conductivity of classical MOFs limit their utilization. Employing graphene-derived nanomaterials with high functional elements as patterns for the MOF materials not only improves the structural instability and poor conductivity but also impedes the restacking and aggregation between graphene layers, thus significantly extending the MOFs application. A review of MOFs-graphene-based material used in food contamination detection is urgently needed for encouraging the advance of this field. Herein, this paper systematically outlines current breakthroughs in MOF-graphene-based nanoprobes, outlines their principles, and illustrates their employments in identifying mycotoxins, heavy metal ions, pathogens, antibiotics, and pesticides, referring to their multiplexing and sensitivity ability. The challenges and limitations of applying MOF-graphene composite for precise and efficient assessment of food were also debated. This paper would maybe offer some inspired concepts for an upcoming study on MOF-based composites in the food security context.

Ultrahigh Content Boron and Nitrogen Codoped Hierarchically Porous Carbon Obtained from Biomass Byproduct Okara for Capacitive Deionization

Capacitive deionization (CDI) is an environmentally friendly, energy efficient, and low cost water purification technique in comparison with other conventional techniques, and it has attracted considerable attention in recent years. Here, we use biomass byproduct okara as the starting material to fabricate a boron and nitrogen codoped hierarchically porous carbon (BNC) with ultrahigh heteroatom contents and abundant in-plane nanoholes for CDI application. With the interconnected hierarchical porous structure, the BNC not only exhibits a large surface area (647.0 m³ g^-1) for the adsorption of ions but also offers abundant ion transport channels to access the entire internal surface. Meanwhile, the ultrahigh dopants' content of B (11.9 at%) and N (14.8 at%) further gives rise to the increased surface polarity and enhanced capacitance for BNC. Owing to these favorable properties, BNC exhibits top-level salt adsorption capacity (21.5 mg g^-1) and charge efficiency (59.5%) at the initial NaCl concentration of ∼500 mg L^-1. Moreover, we performed first-principle simulations to explore the different effects between N-doping and N,B-codoping on the capacitive property, which indicate that the boron and nitrogen codoping of carbon can largely increase the quantum capacitance over the double layer capacitance. The results of this work suggest a promising prospect for the BNC material in practical CDI application.

Molecular Machines and Microrobots: Nanoarchitectonics Developments and On-Water Performances

This review will focus on micromachines and microrobots, which are objects at the micro-level with similar machine functions, as well as nano-level objects such as molecular machines and nanomachines. The paper will initially review recent examples of molecular machines and microrobots that are not limited to interfaces, noting the diversity of their functions. Next, examples of molecular machines and micromachines/micro-robots functioning at the air-water interface will be discussed. The behaviors of molecular machines are influenced significantly by the specific characteristics of the air-water interface. By placing molecular machines at the air-water interface, the scientific horizon and depth of molecular machine research will increase dramatically. On the other hand, for microrobotics, more practical and advanced systems have been reported, such as the development of microrobots and microswimmers for environmental remediations and biomedical applications. The research currently being conducted on the surface of water may provide significant basic knowledge for future practical uses of molecular machines and microrobots.

Metal-Organic Framework-Derived N-Doped Porous Carbon for a Superprotonic Conductor at above 100 °C

The development of proton conductors capable of working at above 100 °C is of great significance for proton exchange membrane electrolysis cells (PEMECs) and proton exchange membrane fuel cells (PEMFCs) but remains to be an enormous challenge to date. In this work, we demonstrate for the first time that the N-doped porous carbon derived from metal-organic frameworks (MOFs) with great superiority can be exploited for high-performing proton conductors at above 100 °C. Through the pyrolysis of ZIF-8, the N-doped porous carbon (ZIF-8-C) featuring high chemical resistance to Fenton's reagent was readily prepared and then served as a robust host to accommodate H₃PO₄ molecules for proton transport. Upon impregnation with H₃PO₄, the resulting PA@ZIF-8-C exhibits low water swelling and high proton conduction of over 10^-2 S cm^-1 at a temperature above 100 °C, which is superior to many reported proton conductors. This work provides a new approach for the design of high-performing proton conductors at above 100 °C.