Stable confinement of Fe/Fe3C in Fe, N-codoped carbon nanotube towards robust zinc-air batteries

Structural design of FeCo alloy implanted into N,S co-doped carbon nanotubes via self-catalyzed growth for advanced liquid and flexible all-state-state Zn-air battery

The introduction of transition bimetallic alloys can effectively improve oxygen reduction reaction (ORR) activity. However, the alloy particles are inclined to dissolve under harsher conditions, resulting in a serious decrease in catalytic activity and stability. Herein, an efficient ORR catalyst, FeCo alloy nanoparticles (NPs) encapsulated in N,S co-doped carbon nanotubes (FeCo10-NSCNTs), was developed through a self-catalyzed growth strategy. Due to the delicate structural design, the N,S co-doped structure can effectively improve the ORR performance by modulating the electronic properties and surface polarity of the carbon substrate, and the randomly connected carbon nanotube structure with large specific surface area can further enhance the adsorption and dissociation of gas molecules, accelerating the kinetics of gas participation in the reaction. Carbon-encapsulated FeCo alloys are beneficial for improving catalytic activity and durability. The FeCo10-NSCNTs displayed excellent ORR activity with a half-wave potential of E1/2 = 0.84 V and robust stability of 13 k cycles. More impressively, the assembled liquid-state Zn-air battery (ZAB) with FeCo10-NSCNTs as the air-electrode delivers an output power density of 146.68 mW cm-2 along with excellent operation durability. The assembled all-solid ZAB has good cyclic stability under 0-180° bending conditions. The synthesized N,S co-doping, carbon nanotubes and FeCo alloys provide important guidance for the construction of cheap non-noble metal-carbon hybrid nanomaterials.

First-Row Transition Metals for Catalyzing Oxygen Redox

Rechargeable zinc-air batteries are widely recognized as a highly promising technology for energy conversion and storage, offering a cost-effective and viable alternative to commercial lithium-ion batteries due to their unique advantages. However, the practical application and commercialization of zinc-air batteries are hindered by the sluggish kinetics of the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Recently, extensive research has focused on the potential of first-row transition metals (Mn, Fe, Co, Ni, and Cu) as promising alternatives to noble metals in bifunctional ORR/OER electrocatalysts, leveraging their high-efficiency electrocatalytic activity and excellent durability. This review provides a comprehensive summary of the recent advancements in the mechanisms of ORR/OER, the performance of bifunctional electrocatalysts, and the preparation strategies employed for electrocatalysts based on first-row transition metals in alkaline media for zinc-air batteries. The paper concludes by proposing several challenges and highlighting emerging research trends for the future development of bifunctional electrocatalysts based on first-row transition metals.

Surface redox pseudocapacitance boosting Fe/Fe3C nanoparticles-encapsulated N-doped graphene-like carbon for high-performance capacitive deionization

The practical application of carbon anode in capacitive deionization (CDI) is greatly hindered by their poor adsorption capacity and co-ion effect. Herein, an N-doped graphene-like carbon (NC) decorated with Fe/Fe₃C nanoparticles composite (Fe/Fe₃C@NC) with large specific surface area and plentiful porosity is fabricated via a facile and scalable method, namely sol-gel method combined with Fe-catalyzed carbonization. As expected, it exhibits superior CDI performance as a Cl-storage electrode, with Cl^- adsorption capacity as high as 102.3 mg g^-1 at 1000 mg L^-1 Cl^- concentration and 1.4 V voltage, and a stable capacity of 68.5 mg g^-1 for 60 cycles in 500 mg L^-1 Cl^- concentration and 100 mA g^-1 current density. More importantly, on the basis of electrochemical tests, ex-situ X-ray diffraction, ex-situ X-ray photoelectron spectroscopy (XPS), and XPS analysis with argon ion depth etching, it is revealed that the chlorine storage mechanism of the Fe/Fe₃C@NC electrode is dominated by the surface-related redox pseudocapacitance behavior of Fe²⁺/Fe³⁺ couple occurring on or near the surface, enabling fast and reversible ion storage. This work proposes an economical and environmentally friendly general method for the design and development of high-performance Cl-storage electrodes for CDI, and offers an in-depth insight into the Cl^- storage mechanism of Fe decorated carbon electrodes, further promoting the development of CDI technology.

Research on Mechanism of miR-488-5p Carried with Magnetic Carbon Nanotubes in Restraining Lymphatic Metastasis in Cervical Cancer Through Induction of mTOR/P70S6K Signaling Pathway

This study intends to discuss mechanism of miR-488-5p carried with magnetic carbon nanotubes (MAGCNTs) in restraining lymphatic metastasis in cervical cancer through induction of mTOR/P70S6K signaling pathway. Fifty female rats were randomly divided into five sets, which included control set, miR-488-5p set, empty carrier set, set of miR-488-5p carrier and inhibitor set. The MAGCNTs were prepared and characterized. Condition and quantity of lymphatic metastasis in cervical cancer, miR-488-5p expression and protein expression of factors related with mTOR/P70S6K signaling transduction pathway were observed. Quantity of lymphatic metastasis in the control set was highest, while quantity of lymphatic metastasis in the set of miR-488-5p and carrier were lowest. Expressions of miR-488-5p in of the miR-488-5p and carrier sets were highest and lowest in the control set, and mTOR/P70S6K expression was reversed. miR-488-5p was carried with multi-walled carbon nanotubes (MWCNTs) and entered into cells more rapidly. There was over expression of miR-488-5p and activity of mTOR/P70S6K signaling pathway was restrained. The information conduction was slowed down, and therefore, the lymphatic metastasis in the cervical cancer was restrained.

Emerging Heterogeneous Supports for Efficient Electrocatalysis

Electrocatalysis plays a fundamental role in many fields, such as metallurgy, medicine, chemical industry, and energy conversion. Anchoring active electrocatalysts with controllable loading and uniform dispersion onto suitable supports has become an attractive topic. This is because the supports can not only have the potential to improve catalytic activity and stability through the interaction between support and catalytic center, but also can reduce precious metal consumption by improving atomic utilization. Herein, recent theoretical and experimental progresses concerning the development of supports to anchor electrocatalytic materials are first reviewed. Next, their controllable syntheses, characterization techniques, metal-support electronic interactions, and structure-performance relationships are presented. Some representative carbon supports and non-carbonaceous supports, as well as recently reported star supports such as 2D supports, single atom catalysts, and self-supported catalysts are also summarized. In addition, the significant role of support in stabilizing and regulating catalytic active sites is particularly emphasized. Finally, challenges, opportunities, key problems, and further promising solutions for supported catalysts are proposed.

Co-Co3O4 encapsulated in nitrogen-doped carbon nanotubes for capacitive desalination: Effects of nano-confinement and cobalt speciation

Capacitive deionization (CDI) has gained increasing attention as an environmentally friendly and energy-efficient technology for brackish water desalination. However, traditional CDI electrodes still suffer from low salt adsorption capacity and unsatisfactory reusability, which inhibit its application for long-term operations. Herein, we present a facile and effective approach to prepare Co and Co₃O₄ nanoparticles co-incorporating nitrogen-doped (N-doped) carbon nanotubes (Co-Co₃O₄/N-CNTs) via a pyrolysis route. The Co-Co₃O₄ nanoparticles were homogeneously in-situ encapsulated in the inner channels of the conductive CNTs to form a novel and efficient CDI electrode for the first time. The encapsulation of Co-Co₃O₄ nanoparticles in CNTs not only inhibits the Co leaching but also significantly enhances the desalination capacity. The morphology, structure, and capacitive desalination properties of the Co-Co₃O₄/N-CNTs were thoroughly characterized to illuminate the nano-confinement effects and the key roles of the interaction between cobalt species in the CDI performance. The co-existing metallic cobalt and cobalt oxides act as the roles of effective active sites in the CDI performance. As a consequence, the optimum Co-Co₃O₄/N-CNTs electrode displays an outstanding desalination capacity of 66.91 mg NaCl g^-1 at 1.4 V. This work provides insights for understanding the nano-confinement effects and the key roles of the interaction between cobalt species on the CDI performance.

Corrosion-Engineered Morphology and Crystal Structure Regulation toward Fe-Based Efficient Oxygen Evolution Electrodes

The rational regulation of catalysts with a well-controlled morphology and crystal structure has been demonstrated effective for optimizing the electrochemical performance. Herein, corrosion engineering was employed for the straightforward preparation of FeAl layered double hydroxide (LDH) nanosheets and Fe₃O₄ nanooctahedrons via the feasible modification of dealloying conditions. The FeAl-LDH nanosheets display an excellent catalytic performance for oxygen evolution reactions in 1 M KOH solution, such as low overpotentials (333 mV on glass carbon electrode and 284 mV on Ni foam at 10 mA cm⁻²), a small Tafel slope (36 mV dec⁻¹), and excellent durability (24 h endurance without deactivation). The distinguished catalytic features of the FeAl-LDH nanosheets comes from the Al and Fe synergies, oxygen vacancies, and well-defined two-dimensional (2D) layered LDH structure.

Ultrafast Porous Carbon Activation Promises High-Energy Density Supercapacitors

Activated porous carbons (APCs) are traditionally produced by heat treatment and KOH activation, where the production time can be as long as 2 h, and the produced activated porous carbons suffer from relatively low specific surface area and porosity. In this study, the fast high-temperature shock (HTS) carbonization and HTS-KOH activation method to synthesize activated porous carbons with high specific surface area of ≈843 m² g^-1 , is proposed. During the HTS process, the instant Joule heating (at a heating speed of ≈1100 K s^-1 ) with high temperature and rapid quenching can effectively produce abundant pores with homogeneous size-distribution due to the instant melt of KOH into small droplets, which facilitates the interaction between carbon and KOH to form controllable, dense, and small pores. The as-prepared HTS-APC-based supercapacitors deliver a high energy density of 25 Wh kg^-1 at a power density of 582 W kg^-1 in the EMIMBF₄ ionic liquid. It is believed that the proposed HTS technique has created a new pathway for manufacturing activated porous carbons with largely enhanced energy density of supercapacitors, which can inspire the development of energy storage materials.

Coupling Co-N-C with MXenes Yields Highly Efficient Catalysts for H2O2 Production in Acidic Media

The electrochemical oxygen reduction reaction (ORR) offers a promising method to replace the anthraquinone process for hydrogen peroxide (H₂O₂) production. However, the efficiency of this process suffers from sluggish kinetics, particularly in an acidic environment. Therefore, employing catalysts with high electroactivity is highly desirable for H₂O₂ synthesis. Here, an effective strategy for preparing Co-N-C/Ti₃C₂T_x with high H₂O₂ selectivity and ORR reactivity is proposed. The acquired Co-N-C/Ti₃C₂T_x shows excellent H₂O₂ electrosynthesis performance in acidic media with H₂O₂ productivity of up to 3200 ppm h^-1, superior to state-of-the-art catalysts. Interestingly, a H₂O₂ concentration of 6.0 wt % was obtained after the stability test, and the Co-N-C/Ti₃C₂T_x catalyst was found to effectively catalyze organic dye degradation. Further analysis reveals that the enhanced H₂O₂ electrosynthesis performance originates from the layered structure and the oxygen functional groups of Ti₃C₂T_x. The layered structure can effectively promote increased exposure of active sites, while the oxygen functional groups will fine-tune the electronic structure of Co atoms, allowing a selective ORR pathway to produce H₂O₂. This work provides a strategy to design and fabricate highly efficient catalysts for H₂O₂ production and degradation of organic pollutants.

Molten salt-assisted synthesis of special open-cell Fe, N co-doped porous carbon as an efficient electrocatalyst for zinc–air batteries

Fe, N co-doped porous carbon (Fe–N–C) with open frame structure is prepared by molten salt-assisted pyrolysis strategy, which exhibits superior ORR performance and high specific capacity.

Ultrathin Co(OH)2 Nanosheets@Nitrogen-Doped Carbon Nanoflake Arrays as Efficient Air Cathodes for Rechargeable Zn-Air Batteries

Developing highly active, cost-effective, and durable bifunctional oxygen electrocatalysts is an important step for the advancement of rechargeable Zn-air batteries (ZABs). Herein, an efficient bifunctional oxygen electrocatalyst of ultrathin Co(OH)₂ nanosheets supported on nitrogen-doped carbon nanoflake arrays (named as Co(OH)₂ @NC), is reported, which yields excellent bifunctional activity, i.e., a low overpotential of 285 mV to reach 10 mA cm^-2 for oxygen evolution reaction (OER), a high half-wave potential (0.83 V) for oxygen reduction reaction (ORR), and a low potential gap (ΔE) of 0.69 V. The excellent bifunctional catalytic performance can be ascribed to the concerted efforts of cobalt hydroxide toward OER and nitrogen-doped carbon for ORR. The Co(OH)₂ @NC nanoflake arrays is further used as binder-free air cathodes for rechargeable Zn-air batteries, exhibiting a high specific capacity of 798.3 mAh g_Zn ^-1 , improved stability (a working life of >70 h at 5 mA cm^-2 ), as well as a reduced long-term charging voltage, which outperforms the counterparts of NC nanoflake arrays and Pt/C-based air cathodes. One step further, the Co(OH)₂ @NC nanoflake arrays on carbon cloth are directly used as binder-free air cathodes for flexible, solid-state ZABs, showing excellent performance under deformation as well.