FeCo alloy entrapped in N-doped graphitic carbon nanotubes-on-nanosheets prepared by coordination-induced pyrolysis for oxygen reduction reaction and rechargeable Zn-air battery

Breaking the symmetry and d-orbital optimization at Co site in CoNC as bifunctional air catalysts for rechargeable liquid and flexible solid-state Zn-air batteries

By utilizing abundant earth metals and incorporating them into N-doped carbon electrocatalysts, the electrochemical kinetics and stability of oxygen reactions in zinc-air batteries (ZABs) are enhanced. However, several challenges remain. We introduce a method that focuses on microenvironmental modulation to precisely adjust the Cr-doped Co NC (Cr-Co NC) catalyst, thereby enhancing its inherent electrochemical activity and durability, and improving the oxygen reaction process. The unique Cr-N-Co configuration in the Cr-CoNC-1.00 catalyst weakens the adsorption strength of *OH intermediates by engineering the Co d-band center, thus lowering the energy barrier for both the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER). The precisely engineered Cr-CoNC-1.00 catalyst demonstrates robust ORR and OER performance, achieving an ORR half-wave potential (E1/2) of 0.865 V and an OER overpotential (EJ=10) of 1.64 V (vs RHE), rivaling that of noble-metal catalysts (Pt/C for ORR and RuO2 for OER). In practical applications, the rechargeable liquid ZABs equipped with Cr-CoNC-1.00 delivered exceptional results (peak power density: 110 mW·cm-2, specific capacity: 816 mA·h·g-1 Zn at 10 mA·cm-2, with over 208 h of charge-discharge cycle stability). Additionally, the flexible solid-state ZABs achieved an open-circuit voltage of 1.4 V, demonstrated remarkable charge-discharge stability for over 12 h, and maintained performance under various bending conditions. This approach highlights the significant potential for developing high-efficiency bifunctional catalysts suitable for flexible zinc-air batteries.

Synergistically driven PdCo alloy based on cross-linked carbon dots for efficient formic acid dehydrogenation

Modifying the electronic structure of precious metals by alloying with non-precious metals is a proven strategy for enhancing the performance of dehydrogenation catalysts. In this work, a PdCo alloy catalyst supported on N-doped carbon dots (NCDs) was synthesized using a straightforward hydrothermal and reduction process. This catalyst effectively promoted the dehydrogenation of formic acid without the need for any additives at 323 K. The confinement effect of NCDs facilitated the formation of uniformly dispersed PdCo alloy particles (average size of 2.7 nm). X-ray photoelectron spectroscopy analysis revealed that the addition of Co not only increases the electron density of Pd but also enhances the electronic support from the electron-rich N atoms in NCDs, thereby significantly improving catalytic activity. Through optimization of the Pd-to-Co molar ratio, it was determined that Pd9Co1/NCDs exhibited superior activity for formic acid dehydrogenation. The turnover frequency of the catalyst was 593 h-1 and the activation energy of the dehydrogenation process was 39.3 kJ·mol-1. This research established an experimental basis for designing noble metal-based catalysts with enhanced catalytic efficiency.

Self-Supported NiCo2S4@Ce-NiFe LDH/CeO2 Nanoarrays for Electrochemical Water Splitting

The design of high-performance OER catalysts is crucial for efficient electrochemical water splitting (EWS). Herein, a NiCo2S4@Ce-NiFe LDH/CeO2 heterostructure nanoarray electrocatalyst with abundant oxygen defect sites is reported. The introduction of Ce species activates the lattice oxygen in the oxyhydroxides, inducing the transformation of the catalytic mechanism toward the lattice oxygen oxidation mechanism (LOM) pathway, bypassing the thermodynamic limitation of the adsorbate evolution mechanism (AEM), and strengthening the intrinsic activity of the material. Moreover, the reversible transitions between different oxidation states of Ce species and the high oxygen storage capacity of CeO2 regulate the adsorption behavior of the reaction intermediates, allowing it to be easier for the material to enrich the oxygen-containing intermediates, thereby improving the adsorption kinetics. Accordingly, NiCo2S4@Ce-NiFe LDH/CeO2 exhibits remarkable OER performance (η50 = 226 mV, η100 = 244 mV) and brilliant stability. Additionally, the presence of the CeO2 protective layer inhibits the impact of Cl- and other pollutants in seawater, which enables NiCo2S4@Ce-NiFe LDH/CeO2 to perform satisfactorily in seawater electrolysis, as well. This study offers a fresh perspective on the design of defect-rich OER catalysts.

Magnetic Hollowed CoFe Alloy@C Prism Catalyst for N-Alkylation of Alcohols and Amines

A novel magnetic hollowed CoFe@C-650 prism catalyst has been successfully prepared and applied in the N-alkylation of alcohols and amines through a hydrogen borrowing strategy. The catalyst demonstrates good to excellent activities in the reaction with a broad substrate scope to afford up to a 99% yield of target products. A preliminary mechanistic study reveals that a high valent Co species in the catalyst may promote the adsorption and conversion of alcohols, while the Fe species assists in hydrogenating the imine intermediates.

Robust Spray Combustion Enabling Hierarchical Porous Carbon-Supported FeCoNi Alloy Catalyst for Zn-Air Batteries

Rechargeable Zn-air batteries (RZABs) are poised for industrial application, yet they require low-cost, high-performance catalysts that efficiently facilitate both the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER). The pivotal challenge lies in designing multimetal active sites and optimizing the carbon skeleton structure to modulate catalyst activity. In this study, we introduce a novel hierarchical porous carbon-supported FeCoNi bifunctional catalyst, synthesized via a spray combustion method. The carbon, derived from sucrose, was tailored into a hierarchical porous morphology through etching with NO3- ions and NaCl, thereby significantly increasing the surface area for the interaction of the O2 and electrolyte interaction. The in situ formation of FeCoNi alloy nanoparticles ensures their uniform dispersion and anchoring, facilitating electron transport. The strong interaction and charge transfer at the heterogeneous FeCoNi alloy interfaces, along with nitrogen doping, which enhances the OER/ORR activity, endow the FeCoNi/N-PC catalyst with exceptional bifunctional catalytic properties, characterized by an activity parameter of 0.73 V. Furthermore, the RZAB assembled with this catalyst demonstrates outstanding cycling stability and reversibility, with a minimal round-trip efficiency decay of 7.6% over 1380 cycles (460 h) at 10 mA cm-2.

Interfacial anchoring cobalt species mediated advanced oxidation: Degradation performance and mechanism of organic pollutants

The development of highly catalytic activity, low-cost and environmentally friendly catalysts is crucial for the use of advanced oxidation processes (AOPs) to treat organic pollutants. In this study, to reduce costs, enhance catalytic activity and avoid secondary pollution form metal ions, pomelo peel was used as raw material, combined with surface crystallization, carbon layer protection and heat treatment technology to effectively construct AOPs catalyst that can efficiently activate peroxymonosulfate (PMS) to degrade harmful organic pollutants. Under the optimal conditions, the Co/BC-PMS system can degrade about 100 % of tetracycline (TC, a spectral antibiotic) within 5 min, and the degradation rate of TC can still reach 100 % even if Co/BC (cobalt anchored on biochar) was reused for 6 times. The Co/BC-PMS system can resist complex environmental conditions, including acidic solution, alkaline solution, coexisting ions, different water quality, and is universal for the degradation of most organic pollutants. The integrated purification column with Co/BC as the core realizes the continuous and complete degradation of organic pollutants and has the ability of practical application. Radical capture and monitoring combined with density-functional-theory calculations confirmed that the Co(111) and amorphous CoO sites in Co/BC are the key to driving PMS to degrade organic pollutants, Co/BC can efficiently adsorb PMS and promote the dissociation of PMS into highly active OH, SO4- and 1O2, and these reactive oxygen species jointly promote the degradation of organic pollutants. This study provides experimental support and theoretical insights for the design of efficient AOPs catalysts, and plays an important role in promoting the development of AOPs.

Bimetallic MIL-88/Polyaniline Hybrid Hollow Structure: In-situ Synthesis and Enhanced Oxygen Evolution Reaction at High Current Densities

Developing oxygen evolution reaction (OER) electrocatalysts in an efficient strategy, while maintaining high catalytic activity and stability under high current densities, remains a crucial problem. In this study, a bimetallic iron-cobalt phytic acid complex loaded with polyaniline hollow structure (FCP@PAn) was successfully constructed, via a progress of selective etching and surface modification in one step without high-temperature phosphating or carbonization. The as-obtained FCP@PAn required only 329 and 385 mV overpotentials at high current densities of 500 and 1000 mA cm-2, respectively, due to phytic acid and polyaniline incorporation and the coordinated effect of each component. Additionally, the FCP@PAn exhibited the lowest Tafel slope values of 44.6 mV dec-1 and was able to continuously operate for 120 h at 500 mA cm-2, displaying high catalytic activity and stability. Hence, the hollow structure of the conductive polymer and MOFs composites provided a new surface modification strategy for transition metal-based catalysts that are prone to dissolution or corrosion during the OER process, as well as for high current density applications.

P-NiFe2O4/N-Doped Carbon Nanotubes/NiFe Multi-Phase Heterojunctions for Overall Water Splitting and Urea Electrolysis

The design and construction of highly efficient electrocatalysts for overall water splitting and urea electrolysis are significantly important for promoting energy conversion and realizing green hydrogen production. In this work, we constructed a multi-phase heterojunction through a simple hydrothermal and phosphorization process. The P-doped NiFe2O4 (P-NiFe2O4) nanoparticles were uniformly anchored on the bamboo-like N-doped carbon nanotubes (NCNTs) grown via a NiFe-alloy autocatalysis. The electronic structure and coordination environment of active species were optimized by the synergistic action of P doping, well-dispersed ultrafine NiFe2O4, and NCNTs matrix with good conductivity, enhancing their quantity and activity for electrocatalysis. Consequently, the P-NiFe2O4/NCNTs/NiFe exhibits excellent HER and OER activities with an overpotential of 111 and 266 mV at 10 mA cm-2 in 1 M KOH, respectively. The symmetrical overall water-splitting cell using P-NiFe2O4/NCNTs/NiFe as both anode and cathode delivers 10 mA cm-2 at a voltage of 1.604 V in 1 M KOH. Notably, the two-electrode cell requires a low voltage of 1.467 V to achieve a current density of 10 mA cm-2 in 1 M KOH solution with 0.6 M urea. This designed catalysts display outstanding reaction kinetics and catalytic stability. This work provides useful guidance for applying transition metal-based catalysts for hydrogen production.

Tailoring phases of ferrihydrite/α-Fe2O3@C nanocomposites using syringyl and guaiacyl-rich biomass-derived carbon nanodots for electrochemical application

Biomass-derived carbon nanodots (CNDs) hold promise as effective reducing agents for metal oxide nanoparticles yet understanding the intricate interplay with CND structure remains challenging. This study explores the impact of lignin types, specifically syringyl (S), and guaiacyl (G) units in CNDs on metal oxide phases and their electrochemical activity toward dopamine oxidation. We design phases of ferrihydrite/α-Fe2O3@C nanocomposites, using hazelnut carbon nanodots (HS-CNDs (S-rich)) and beetroot carbon nanodots (BS-CNDs (G-rich)) via a one-pot hydrothermal technique. Our findings show S units in HS-CNDs promote α-FeOOH/α-Fe2O3@CHS, while G units in BS-CNDs favor α (β)-FeOOH/α-Fe2O3@CBS. In contrast to α(β)-FeOOH/α-Fe2O3@CBS, α-FeOOH/α-Fe2O3@CHS exhibits superior electrochemical performance in dopamine oxidation due to its larger electrochemical active surface area, higher absorbance capacity, and shortened electron transfer length. Moreover, α-FeOOH/α-Fe2O3@CHS nanocomposites demonstrate remarkable dopamine selectivity, achieving rapid detection response in 10 s with a low LOD of 4 nM within a broad linear range (0.05-0.3 μM), demonstrating impressive reproducibility (97.5 %), stability (96.4 %), and works in real-time human urine detection with a recovery rate of ranging from 94.57 % and 102.2 %. Therefore, the utilization of biomass-derived CNDs, particularly S and G units-rich CNDs, in tailoring the phases of ferrihydrite/α-Fe2O3@C nanocomposites for electrochemical dopamine detection is promising.

Modulation in work function of CoTe as bifunctional electrocatalyst for rechargeable zinc air battery

The sluggish kinetics and inferior stability of oxygen electrocatalyst in rechargeable zinc air battery (ZAB) hamper its industrialization. In this work, we activate cobalt telluride (CoTe) by introduction of metallic cobalt (Co) to modulate the work function to facilitate the electron transfer from Co to CoTe during oxygen catalysis; additionally, the three-dimensional porous carbon nanosheets (3DPC) are invited to reduce the resistance towards electrolyte/oxygen diffusion. Thereby, Co-CoTe@3DPC only demands 280 mV overpotential to reach 10 mA cm-2 under alkaline oxygen evolution reaction (OER) condition, relatively lower than commercial iridium oxides (IrO2); besides, the operando electrochemical impedance spectroscopy (EIS) indicates a better resistance towards surface reconstruction than Co@3DPC leading to a superior stability. A Pt-like oxygen reduction reaction (ORR) performance, half-wave potential associated with kinetic current density, is achieved for Co-CoTe@3DPC. A maximum power density of 203 mW cm-2 is achieved and sustains for 800 h. Furthermore, the all-solid-state ZAB offers 97 mW cm-2. Theoretical calculation suggests that the incorporation of metallic Co to CoTe maintains the superb ORR activity and promotes the OER catalysis.

In-situ construction of iron-modified nickel nanoparticles assisted by hexamethylenetetramine with the internal and external collaboration for highly selective electrocatalytic carbon dioxide reduction

Carbon dioxide (CO2) electroreduction provides a sustainable route for realizing carbon neutrality and energy supply. Up to now, challenges remain in employing abundant and inexpensive nickel materials as candidates for CO2 reduction due to their low activity and favorable hydrogen evolution. Here, the representative iron-modified nickel nanoparticles embedded in nitrogen-doped carbon (Ni1-Fe0.125-NC) with the porous botryoid morphology were successfully developed. Hexamethylenetetramine is used as nitrogen-doped carbon source. The collaboration of internal lattice expansion with electron effect and external confinement effect with size effect endows the significant enhancement in electrocatalytic CO2 reduction. The optimized Ni1-Fe0.125-NC exhibits broad potential ranges for continuous carbon monoxide (CO) production. A superb CO Faradaic efficiency (FECO) of 85.0 % realized at -1.1 V maintains a longtime durability over 35 h, which exceeds many state-of-the-art metal catalysts. Theoretical calculations further confirm that electron redistribution promotes the desorption of CO in the process for favorable CO production. This work opens a new avenue to design efficient nickel-based materials by considering the intrinsic structure and external confinement for CO2 reduction.

Tailored interface engineering of Co3Fe7/Fe3C heterojunctions for enhancing oxygen reduction reaction in zinc-air batteries

The rational construction of highly active and robust non-precious metal oxygen reduction electrocatalysts is a vital factor to facilitate commercial applications of Zn-air batteries. In this study, a precise and stable heterostructure, comprised of a coupling of Co3Fe7 and Fe3C, was constructed through an interface engineering-induced strategy. The coordination polymerization of the resin with the bimetallic components was meticulously regulated to control the interfacial characteristics of the heterostructure. The synergistic interfacial effects of the heterostructure successfully facilitated electron coupling and rapid charge transfer. Consequently, the optimized CST-FeCo displayed superb oxygen reduction catalytic activity with a positive half-wave potential of 0.855 V vs. RHE. Furthermore, the CST-FeCo air electrode of the liquid zinc-air battery revealed a large specific capacity of 805.6 mAh gZn-1, corresponding to a remarkable peak power density of 162.7 mW cm-2, and a long charge/discharge cycle stability of 220 h, surpassing that of the commercial Pt/C catalyst.

Bimetal Oxides Anchored on Carbon Nanotubes/Nanosheets as High-Efficiency and Durable Bifunctional Oxygen Catalyst for Advanced Zn-Air Battery: Experiments and DFT Calculations

To meet increasing requirement for innovative energy storage and conversion technology, it is urgent to prepare effective, affordable, and long-term stable oxygen electrocatalysts to replace precious metal-based counterparts. Herein, a two-step pyrolysis strategy is developed for controlled synthesis of Fe2O3 and Mn3O4 anchored on carbon nanotubes/nanosheets (Fe2O3-Mn3O4-CNTs/NSs). The typical catalyst has a high half-wave potential (E1/2 = 0.87 V) for oxygen reduction reaction (ORR), accompanied with a smaller overpotential (η10 = 290 mV) for oxygen evolution reaction (OER), showing substantial improvement in the ORR and OER performances. As well, density functional theory calculations are performed to illustrate the catalytic mechanism, where the in situ generated Fe2O3 directly correlates to the reduced energy barrier, rather than Mn3O4. The Fe2O3-Mn3O4-CNTs/NSs-based Zn-air battery exhibits a high-power density (153 mW cm-2) and satisfyingly long durability (1650 charge/discharge cycles/550 h). This work provides a new reference for preparation of highly reversible oxygen conversion catalysts.

Simultaneous ionic cobalt sensing and toxic Congo red dye removal: a circular economic approach involving silver-enhanced fluorescence

A highly fluorescent quinone-capped silver hydrosol (AgOSA) was obtained using salicylaldehyde and an ionic silver solution. Such metal-enhanced fluorescence was efficiently quenched with Congo red dye (CR), producing CRAgOSA, due to the strong silver-sulfur interaction, replacing the capping of quinone (oxidized salicylaldehyde). The introduction of cobalt ions restored the fluorescence by engaging CR (CoCRAgOSA). Cobalt-induced fluorescence enhancement was 8.3 times higher than that of AgOSA due to the freeing of CR and the release of self-quenching of excess quinone molecules in CoCRAgOSA. The mammoth and selective fluorescence enhancement with ionic cobalt assisted in designing a turn-on ionic cobalt sensor with a limit of detection (LOD) of 9.4 × 10-11 M and a linear detection range (5 × 10-5 to 10-9 M). Moreover, toxic CR dye was eliminated by quinone-capped silver nanoparticles and Co2+ due to chemisorption. Not only the fluorimetric sensing of ionic cobalt but also the colorimetric sensing of Hg2+ was designed due to the simultaneous aggregation of AgNPs and complexation with CR induced by Hg2+ (LOD 1.36 × 10-5 M and linear detection range from 1.00 × 10-4 to 5 × 10-7 M). We applied our sensing method to estimate ionic cobalt and mercury in natural samples. The experiment was a unique case of circular economy, where a toxic dye was used for making a nanosensor.

Iodine intercalation-assisted alkali activation constructs coal-based porous carbon for high-performance supercapacitors

Supercapacitors have the advantages of fast charging and discharging speeds, high power density, long cycle life, and wide operating temperature range. They are widely used in portable electronic equipment, rail transit, industry, military, aerospace, and other fields. The design and preparation of low-cost, high-performance electrode materials still pose a bottleneck that hinders the development of supercapacitors. In this paper, coal was used as the raw material, and the coal-based porous carbon electrode material was constructed using the iodine intercalation-assisted activation method and used for supercapacitors. The CK-700 electrode exhibits excellent charge storage performance in a 6 M potassium hydroxide (KOH) electrolyte, with a maximum specific capacitance of 350 F/g at a current density of 0.5 A/g. In addition, it has an excellent rate performance (310 F/g at 1 A/g) and cycle stability (capacitance retention up to 91.7 % after 30000 cycles). This work provides a method for realizing high-quality, high-yield and low-cost preparation of coal-based porous carbon, and an idea for improving the performance of supercapacitors.

Atomically dispersed bimetallic active sites as H2O2 self-supplied nanozyme for effective chemodynamic therapy, chemotherapy and starvation therapy

Tumor microenvironment (TME)-responsive chemodynamic therapy (CDT) is severely hindered by insufficient intracellular H2O2 level that seriously deteriorates antitumor efficacy, albeit with its extensively experimental and theoretical research. Herein, we designed atomically dispersed FeCo dual active sites anchored in porous carbon polyhedra (termed FeCo/PCP), followed by loading with glucose oxidase (GOx) and anticancer doxorubicin (DOX), named FeCo/PCP-GOx-DOX, which converted glucose into toxic hydroxyl radicals. The loaded GOx can either decompose glucose to self-supply H2O2 or provide fewer nutrients to feed the tumor cells. The as-prepared nanozyme exhibited the enhanced in vitro cytotoxicity at high glucose by contrast with those at less or even free of glucose, suggesting sufficient accumulation of H2O2 and continual transformation to OH for CDT. Besides, the FeCo/PCP-GOx-DOX can subtly integrate starvation therapy, the FeCo/PCP-initiated CDT, and DOX-inducible chemotherapy (CT), greatly enhancing the therapeutic efficacy than each monotherapy.

Building synergistic multiple active sites in branch-leaf nanostructured carbon nanofiber derived from MOF/COF hybrid for flexible wearable Zn-air battery

Covalent organic frameworks (COFs) and metal-organic frameworks (MOFs) have attracted growing attention in electrochemical energy storage and conversion systems (e.g., Zn-air batteries, ZABs) owing to their structural tunability, ordered porosity and high specific surface area. In this work, for the first time, the three-dimensional (3D) highly open catalyst (CNFs/CoZn-MOF@COF) possessing hierarchical porous structure and high-density active sites of uniform cobalt (Co) nanoparticles and metal-Nx (M-Nx, M = Co and Zn) is demonstrated, which is fabricated using electrospinning technique in combination with MOF/COF hybridization strategy and direct pyrolysis. Benefiting from the well-designed branch-leaf nanostructures, plentiful and uniform active sites on the MOF/COF-derived carbon frameworks, as well as the synergistic effect of multiple active sites, CNFs/CoZn-MOF@COF catalyst achieves superior electrocatalytic activity and stability towards both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) with a small potential gap (ΔE = 0.75 V). In situ Raman spectroscopy and X-ray photoelectron spectroscopy results indicate that the CoOOH intermediates are the main active species during OER/ORR. Significantly, both aqueous and all-solid-state rechargeable ZABs assembled with CNFs/CoZn-MOF@COF as the air cathode show high open-circuit potential, outstanding peak power density, large capacity and long cycle life. More impressively, the obtained all-solid-state ZAB also displays superb mechanical flexibility and device stability under different, showcasing great application deformations potential in portable and wearable electronics. This work provides a new insight into the design and exploitation of bifunctional catalysts from MOF/COF hybrid materials for energy storage and conversion devices.

Chemical inertness conversion of carbon fraction in coal gangue via N-doping for efficient benzo(a)pyrene degradation

Efficient degradation of organic pollutants in complex media via advanced oxidation processes (AOPs) is still critical and challenging. Herein, nitrogen (N)-doped coal gangue (CG) catalysts (N-CG) with economic competitiveness and environmental friendliness were successfully synthesized to activate peroxymonosulfate (PMS), exhibiting ultrafast degradation performance toward benzo(a)pyrene (BaP) with 100.00 % and 93.21 % in contaminated solution and soil under optimized condition, respectively. In addition, 0.4 N-CG possessed excellent reusability toward BaP degradation with over 80.00 % after five cycles. However, BaP removal efficiency was significantly affected by some co-existing anions (HCO3- and SO42-) and humic acid (HA) in solution and soil, as well as inhibited under alkaline conditions, especially pH ≥ 9. According to the characterizations, N-doping could promote the generation of pyridinic N and graphitic N in N-CG via high-temperature calcination, which was conducive to produce hydroxyl radical (•OH), sulfate radical (SO4•-), superoxide radical (•O2-) and single oxygen (1O2). In 0.4 N-CG/PMS system, 1O2 and •O2- were proved to be the predominant reactive oxygen species (ROSs) in BaP degradation, as well as •OH and SO4•- made certain contributions. To sum up, this work provided a promising strategy for synthesis of CG-based catalysts by chemical inertness conversion of carbon fracture via N-doping for PMS activation and opened a novel perspective for environmental remediation of hydrophobic and hydrophilic contaminants pollution.

Recent Advances in Catalyst Design and Performance Optimization of Nanostructured Cathode Materials in Zinc-Air Batteries

This review focuses on the advanced design and optimization of nanostructured zinc-air batteries (ZABs), with the aim of boosting their energy storage and conversion capabilities. The findings show that ZABs favor porous nanostructures owing to their large surface area, and this enhances the battery capacity, catalytic activity, and life cycle. In addition, the nanomaterials improve the electrical conductivity, ion transport, and overall battery stability, which crucially reduces dendrite growth on the zinc anodes and improves cycle life and energy efficiency. To obtain a superior performance, the importance of controlling the operational conditions and using custom nanostructural designs, optimal electrode materials, and carefully adjusted electrolytes is highlighted. In conclusion, porous nanostructures and nanoscale materials significantly boost the energy density, longevity, and efficiency of Zn-air batteries. It is suggested that future research should focus on the fundamental design principles of these materials to further enhance the battery performance and drive sustainable energy solutions.

Self-Assembly Strategy for Constructing Porous Boron and Nitrogen Co-Doped Carbon as an Efficient ORR Electrocatalyst toward Zinc-Air Battery

Carbon nanomaterials doped with N and B could activate nearby carbon atoms to promote charge polarization through the synergistic coupling effect between N and B atoms, thus facilitating adsorption of O2 and weakening O-O bond to enhance oxygen reduction reaction. Herein, a simple and controllable self-assembly strategy is applied to synthesize porous B, N co-doped carbon-based catalysts (BCN-P), which employs the macrocyclic molecule cucurbit[7]uril (CB7) as nitrogen source, and 3D aromatic-like closo-[B12H12]2- as boron source. In addition, polystyrene microspheres are added to help introduce porous structure to expose more active sites. Benefitting from porous structures and the synergistic coupling effect between N and B atoms, BCN-P has a high onset potential (Eonset=0.846 V) and half-wave potential (E1/2=0.74 V) in alkaline media. The zinc-air battery assembled with BCN-P shows high operating voltage (1.42 V), peak power density (128.7 mW cm-2) and stable charge/discharge cycles, which is even comparable with Pt/C.

Noble metal-free FeCoNiMnV high entropy alloy anchored on N-doped carbon nanotubes with prominent activity and durability for oxygen reduction and zinc-air batteries

Efficient and stable oxygen reduction reaction (ORR) catalysts are essential for constructing reliable energy conversion and storage devices. Herein, we prepared noble metal-free FeCoNiMnV high-entropy alloy supported on nitrogen-doped carbon nanotubes (FeCoNiMnV HEA/N-CNTs) by a one-step pyrolysis at 800 °C, as certificated by a set of characterizations. The graphitization degree of the N-CHTs was optimized by tuning the pyrolysis temperature in the control groups. The resultant catalyst greatly enhanced the ORR characteristics in the alkaline media, showing the positive onset potential (Eonset) of 0.99 V and half-wave potential (E1/2) of 0.85 V. More importantly, the above FeCoNiMnV HEA/N-CNTs assembled Zn-air battery exhibited a greater open-circuit voltage (1.482 V), larger power density (185.12 mW cm-2), and outstanding cycle stability (1698 cycles, 566 h). This study provides some valuable insights on developing sustainable ORR catalysts in Zn-air batteries.

Electrospinning-derived transition metal/carbon nanofiber composites as electrocatalysts for Zn-air batteries

The sluggish kinetics of the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) significantly impede the broader implementation of Zn-air batteries (ZABs), underscoring the necessity for advanced high-efficiency materials to catalyze these electrochemical processes. Recent advancements have highlighted the potential of transition metal/carbon nanofiber (TM/CNF) composite materials, synthesized via electrospinning technology, due to their expansive surface area, profusion of active sites, and elevated catalytic efficacy. This review comprehensively examines the structural characteristics of TM/CNFs, with a particular emphasis on the pivotal role of electrospinning technology in fabricating diverse structural configurations. Additionally, it delves into the mechanistic underpinnings of various strategies aimed at augmenting the catalytic activity of TM/CNFs. A meticulous discourse is also presented on the application scope of TM/CNFs in the realm of electrocatalysis, with a special focus on their impact on the performance of assembled ZABs. Lastly, this review encapsulates the challenges and future prospects in the development of TM/CNF composite materials via electrospinning, aiming to provide an exhaustive understanding of the current state of research in this domain and to foster further advancements in the commercialization of ZABs.

Methanol-induced assembly and pyrolysis preparation of three-dimensional N-doped interconnected open carbon cages supported FeNb2O6 nanoparticles for boosting oxygen reduction reaction and Zn-air battery

Three-dimensional (3D) hollow carbon is one of advanced nanomaterials widely applied in oxygen reduction reaction (ORR). Herein, iron niobate (FeNb2O6) nanoparticles supported on metal-organic frameworks (MOFs)-derived 3D N-doped interconnected open carbon cages (FeNb2O6/NICC) were prepared by methanol induced assembly and pyrolysis strategy. During the fabrication process, the evaporation of methanol promoted the assembly and cross linkage of ZIF-8, rather than individual particles. The assembled ZIF-8 particles worked as in-situ sacrificial templates, in turn forming hierarchically interconnected open carbon cages after high-temperature pyrolysis. The as-made FeNb2O6/NICC showed a positive onset potential of 1.09 V and a half-wave potential of 0.88 V for the ORR, outperforming commercial Pt/C under the identical conditions. Later on, the as-built Zn-air battery with the FeNb2O6/NICC presented a greater power density of 100.6 mW cm-2 and durable long-cycle stability by operating for 200 h. For preparing 3D hollow carbon materials, this synthesis does not require a tedious removal process of template, which is more convenient than traditional method with silica and polystyrene spheres as templates. This work affords an exceptional example of developing 3D N-doped interconnected hollow carbon composites for energy conversion and storage devices.

Dendritic-like MXene quantum dots@CuNi as an efficient peroxidase candidate for colorimetric determination of glyphosate

Oxidized MXene quantum dots@CuNi bimetal (MQDs@CuNi) were firstly prepared through a simple hydrothermal method. Compared to the controlled samples, MQDs@CuNi1:1 showed the highest peroxidase-like activity. The catalytic mechanism of MQDs@CuNi1:1 was investigated using a steady-state fluorescence analysis, which showed that MQDs@CuNi1:1 efficiently decomposes H2O2 and produces highly reactive hydroxyl radicals (OH). Furthermore, theoretical calculations showed that the remarkable catalytic activity of MQDs@CuNi1:1 originates from the interaction between CuNi bimetal and MQDs to promote the activation and decomposition of H2O2, making it easier to combine with the hydrogen at the end of 3,3',5,5'-Tetramethylbenzidine (TMB). Accordingly, a sensitive colorimetric sensor is proposed to detect glyphosate (Glyp), displaying a low detection limit of 1.13 µM. The work will provide a new way for the development of high-performance nanozyme and demonstrate potential applicability for the determination of pesticide residues in environment.

Sleep deprivation boosts O2·- levels in the brains of mice as visualized by a Golgi apparatus-targeted ratiometric fluorescence nanosensor

Sleep deprivation (SD) is highly prevalent in the modern technological world. Emerging evidence shows that sleep deprivation is associated with oxidative stress. At the organelle level, the Golgi apparatus actively participates in the stress response. In this study, to determine whether SD and Golgi apparatus stress are correlated, we rationally designed and fabricated a novel Golgi apparatus-targeted ratiometric nanoprobe called Golgi dots for O2·- detection. This probe exhibits high sensitivity and selectivity in cells and brain slices of sleep-deprived mice. Golgi dots can be readily synthesized by coprecipitation of Golgi-F127, an amphiphilic polymer F127 modified with a Golgi apparatus targeting moiety, caffeic acid (CA), the responsive unit for O2·-, and red emissive carbon nanodots (CDs), which act as the reference signal. The fluorescence emission spectrum of the developed nanoprobe showed an intense peak at 674 nm, accompanied by a shoulder peak at 485 nm. As O2·- was gradually added, the fluorescence at 485 nm continuously increased; in contrast, the emission intensity at 674 nm assigned to the CDs remained constant, resulting in the ratiometric sensing of O2·-. The present ratiometric nanoprobe showed high selectivity for O2·- monitoring due to the specific recognition of O2·- by CA. Moreover, the Golgi dots exhibited good linearity with respect to the O2·- concentration within 5 to 40 μM, and the limit of detection (LOD) was ~ 0.13 μM. Additionally, the Golgi dots showed low cytotoxicity and an ability to target the Golgi apparatus. Inspired by these excellent properties, we then applied the Golgi dots to successfully monitor exogenous and endogenous O2·- levels within the Golgi apparatus. Importantly, with the help of Golgi dots, we determined that SD substantially elevated O2·- levels in the brain.

Confined Synthesis of Dual-Atoms Within Pores of Covalent Organic Frameworks for Oxygen Reduction Reaction

Dual-atom catalysts exhibit higher reactivity and selectivity than the single-atom catalysts. The pyrolysis of bimetal salt precursors is the most typical method for synthesizing dual-atomic catalysts; however, the finiteness of bimetal salts limits the variety of dual-atomic catalysts. In this study, a confined synthesis strategy for synthesizing dual-atomic catalysts is developed. Owing to the in situ synthesis of zeolitic imidazolate frameworks in the pores of covalent organic frameworks (COFs), the migration and aggregation of metal atoms are suppressed adequately during the pyrolysis process. The resultant catalyst contains abundant Zn─Co dual atomic sites with 2.8 wt.% Zn and 0.5 wt.% Co. The catalyst exhibits high reactivity toward oxygen reduction reaction with a half-wave potential of 0.86 V, which is superior to that of the commercial Pt/C catalyst. Theoretical calculations reveal that the Zn atoms in the Zn─Co dual atomic sites promote the formation of intermediate OOH*, and thus contribute to high catalytic performance. This study provides new insights into the design of dual-atom catalysts using COFs.

In Situ Electrodeposition of Ultralow Pt into NiFe-Metal-Organic Framework/Nickel Foam Nanosheet Arrays as a Bifunctional Catalyst for Overall Water Splitting

Exploring highly effective bifunctional electrocatalysts with surface structural advantages and synergistic optimization effects among multimetals is greatly important for overall water splitting. Herein, we successfully synthesized Pt-loaded NiFe-metal-organic framework nanosheet arrays grown on nickel foam (Pt-NiFe-MOF/NF) via a facile hydrothermal-electrodeposition process. Benefiting from large exposed specific surface, optimal electrical conductivity and efficient metal-support interaction endow Pt-NiFe-MOF/NF with highly catalytic performance, exhibiting small overpotential of 261 mV toward oxygen evolution reaction and 125 mV toward hydrogen evolution reaction at a current density of 100 mA cm-2 in alkaline medium. More significantly, the assembled water electrolyzer comprising the Pt-NiFe-MOF/NF//Pt-NiFe-MOF/NF couple demands a low cell voltage of 1.45 V to reach 10 mA cm-2. This work renders a viable approach to design dual-functional electrocatalysts with exceptional electrocatalytic activity and stability at high current density, showing the great prospect of water electrolysis for commercial application.

Three-dimensional ordered macroporous design of heterogeneous cobalt-iron phosphides as oxygen evolution electrocatalyst

Oxygen evolution reaction (OER) plays a key role in electrochemical conversion, which needs efficient and economical electrocatalyst to boost its kinetics for large-scale application. Herein, a bimetallic CoP/FeP2heterostructure with a three-dimensional ordered macroporous structure (3DOM-CoP/FeP2) was synthesized as an OER catalyst to demonstrate a heterogeneous engineering induction strategy. By adjusting the electron distribution and producing a lot of active sites, the heterogeneous interface enhances catalytic performance. High specific surface area is provided by the 3DOM structure. Additionally, at the solid-gas-electrolyte threephase interface, the electrocatalytic reaction exhibits good mass transfer.In situRaman spectroscopy characterization revealed that FeOOH and CoOOH reconstructed from CoP/FeP2were the true OER active sites. Consequently, the 3DOM-CoP/FeP2demonstrates superior OER activity with a low overpotentials of 300/420 mV at 10/100 mA cm-2and meritorious OER durability. It also reveals promising performance as the overall water splitting anode.

Tandem effect at snowflake-like cuprous sulphide interfaces for highly selective conversion of carbon dioxide to formate by electrochemical reduction

Electrochemical carbon dioxide reduction (ECR) is a commercially promising technology to resolve the energy dilemma and accomplish carbon recycling. Herein, a novel electrocatalyst has been investigated to produce formate (HCOOH) highly selectively during ECR by loading SnO2@C onto cuprous sulphide (Cu2S) to form a triplet effect at the interface. Snowflake-like Cu2S significantly enhances the local concentration of carbon dioxide (CO2) and promotes the binding of CO2 with SnO2, and the addition of carbon spheres enhances the electron transport, which is beneficial to the conversion of CO2 to HCOOH products. The snowflake-like Cu2S loaded with 1 wt% SnO2@C had an HCOOH Faraday Efficiency of 88% at -1.0 V (vs. Reversible Hydrogen Electrode, RHE), and the current density for CO2 reduction was stabilized at 15.6 mA cm-2, which was much higher than the HCOOH Faraday efficiency (FE) of 31.0% for pure Cu2S accompanied by a CO2 reduction current density of 3.9 mA cm-2. Combined investigations using in-situ Fourier transform infrared spectroscopy (FT-IR) with in-situ Raman spectra reveal that the active species is Cu+. Cu2S/1%SnO2@C can effectively promote the adsorption and activation of carbonate and inhibit the production of CO intermediates. The corresponding density functional theory (DFT) demonstrates that Cu2S/1%SnO2@C can well stabilize the HCOO* intermediate during the ECR process. The interaction between Cu2S and SnO2@C adjusts the surface electronic distribution and accelerates electron transfer, which efficiently improves CO2-to-HCOOH conversion. The result obtained from this work provides a simple and efficient electrocatalyst to enhance the HCOOH selectivity of ECR.

A facile and efficient method for preparing La-doped Co3O4 by electrodeposition as an efficient air cathode in rechargeable zinc-air batteries: Role of oxygen vacancies

A rechargeable zinc-air battery (ZAB) is a promising candidate for simple and low-cost energy storage systems. However, preparing the air cathode material using a binder-free method and a bifunctional catalyst is still the major challenge in the field. Herein, we demonstrate the effect of different La contents doped into the Co3O4 spinel structure in the presence of oxygen vacancies prepared by a facile and efficient electrodeposition technique on the oxygen evolution reaction (OER), oxygen reduction reaction (ORR), and ZAB performance. Incorporating the La dopant into the Co3O4 improves the OER and ORR performances and thus enhances the specific capacity and energy density of ZAB. The optimal La-doping amount in the CoLa-1 catalyst demonstrates high feasibility for practical application with a capacity of 780 ± 24 mAh/g and an energy density of 901 ± 39 mW g-1, significantly outperforming the pristine Co3O4. The stability and cycling tests reveal good durability performance after 300 cycles and 100 h of testing without degradation, which is much more stable than the benchmark Pt/C + RuO2 electrode. The performance enhancement is attributed to the synergetic effect of high active surface area, low charge transfer resistance, and optimal oxygen vacancies. A kinetic micromechanism is proposed to illustrate the importance of the oxygen vacancy amount in trapping oxygen gas and maximizing the number of ORR and OER reactions.

Co3Fe7/CoCx nanoparticles encapsulated in nitrogen-doped carbon nanotubes synergistically promote the oxygen reduction reaction in Zn-air batteries

Efficient and stable non-precious metal catalysts (NPMCs) for the oxygen reduction reaction (ORR) are crucial for the advancement of Zn-air batteries. Herein, we report a supramolecular self-scarifying template and confinement pyrolysis strategy to obtain an efficient ORR catalyst of well-dispersed Co3Fe7/CoCx heterostructure nanoparticles encapsulated by nitrogen-doped carbon nanotubes (Co3Fe7/CoCx@N-CNT). The as-synthesized Co3Fe7/CoCx@N-CNT catalyst exhibited outstanding ORR activity, with a half-wave potential of 0.88 V versus a reversible hydrogen electrode, and good stability. The Zn-air battery based on the Co3Fe7/CoCx@N-CNT cathode achieved a peak power density of 265 mW cm-2 and a durability of over 200 h, which is superior to most reported NPMCs and even the Pt/C counterpart. The physical characterization and electrochemical poisoning experiments revealed that the Co3Fe7/CoCx nanoparticles in the core along with pyridine N and Fe-Nx hosted in the carbon nanotube all acted as active sites for the ORR. Further theoretical calculations showed that the charge redistribution between the Co3Fe7/CoCx nanoparticles and the Fe-Nx carbon overlayers downshifted the d-band center of Fe and optimized the adsorption ability, which boosted the ORR kinetics. This work provides an effective strategy to synthesize non-precious metal ORR catalysts with multiple active sites and highlights the synergistic role of encapsulated nanoparticles and carbon support.

Cheap and portable paper chip with terrific oxidase-like activity and SERS enhancement performance for SERS-colorimetric bimodal detection of intracellular glutathione

Glutathione (GSH) acts a crucial role in the normal operation of manifold life activities and is closely bound up with many human diseases. Here, a SERS-colorimetric bimodal paper-based biosensor based on Mn-doped CDs/silver nanoparticles (Mn-CDs/AgNPs) has been fabricated for high-efficiency quantification of intracellular GSH. The Mn-CDs/AgNPs with fine oxidase-like characteristic and SERS enhancement ability has been assembled onto the Whatman filter paper (WFP) to cleverly fabricate paper chip (Mn-CDs/AgNPs@WFP) which can trigger the oxidation of colorless 3,3',5,5'-tetramethylbenzidine (TMB) into blue TMBox and simultaneously enhance the SERS signal of TMBox. However, the introduction of GSH inhibits the oxidation of TMB, leading to color fading of paper chip and diminishment of SERS signal. Considering this, the bimodal paper-based sensing platform can be exploited for SERS-colorimetric detection of GSH, manifesting excellent selectivity, reliable stability, and satisfactory precision. The detection limits of SERS and colorimetric detection modes are as low as 0.41 μM and 0.53 μM, respectively. Furthermore, this proposed bimodal biosensor has been successfully utilized for the determination of intracellular GSH and validated by commercial GSH assay kit, which provides a mighty and convenient tool for intracellular GSH detection and can boost future effort about exploitation of other multimode paper-based biosensors as well as promote their appliances in disease diagnosis.

Poly(ionic liquid)-coated hydroxy-functionalized carbon nanotube nanoarchitectures with boosted catalytic performance for carbon dioxide cycloaddition

Poly(ionic liquid)s (PILs) bearing high ionic densities are promising candidates for carbon dioxide (CO2) fixation. However, efficient and metal-free methods for boosting the catalytic efficiencies of PILs are still challenging. In this study, a novel family of poly(ionic liquid)-coated carbon nanotube nanoarchitectures (CNTs@PIL) were facilely prepared via a noncovalent and in-situ polymerization method. The effects of different carbon nanotubes (CNTs) and PILs on the structure, properties, and catalytic performance of the composite catalysts were systematically investigated. Characterizations and experimental results showed that hybridization of PIL with hydroxyl- or carboxyl-functionalized CNTs (CNT-OH, CNT-COOH) endows the composite catalyst with increased porosity, CO2 capture capacity, swelling ability and diffusion rate with respect to individual PIL, and allows the CNTs@PIL to provide H-bond donors for the synergistic activation of epoxides at the interfacial layer. Benefiting from these merits, the optimal composite catalyst (CNT-OH@PIL) delivered a super catalytic efficiency in the cycloaddition of CO2 to propylene oxide, which was over 4.5 times that of control PIL under metal- and co-catalyst free conditions. Additionally, CNT-OH@PIL showed high carbon dioxide/nitrogen (CO2/N2) adsorptive selectivity and could smoothly catalyze the cycloaddition reaction with a simulated flue gas (15% CO2 and 85% N2). Furthermore, the CNT-OH@PIL exhibited broad substrate tolerance and could be readily recycled and efficiently reused at least 12 times. Hybridization of PIL with functionalized CNTs provides a feasible approach for boosting the catalytic performance of PIL-based solid catalysts for CO2 fixation.

Modulating Electronic Structures of Bimetallic Co-Fe Sulfide Ultrathin Nanosheet Supported on g-C3N4 Promoting Electrocatalytic Hydrogen Evolution Performance

Heteroatom doping is a possible way to regulate the catalytic capability of electrocatalysts for hydrogen evolution reaction (HER). This work focuses on the development of bimetallic Cobalt-Iron sulfide ultrathin nanosheets supported on the graphitic carbon nitride (g-C3N4) catalyst as efficient HER electrocatalysts (CoS2/FeS2/CN) with good stability at wide pH value. The ultrathin nanosheet exposes more active sites and enhances the catalyst activity. Electrochemical experiments demonstrate that adding g-C3N4 and Fe to CoS2 increases its catalytic activity and stability. Furthermore, g-C3N4 and Fe co-doped with CoS2 can modulate electronic structures on the interface. The CoS2/FeS2/CN exhibits outstanding HER performance, reaching a current density of 10 mA cm-2 with overpotentials of only 76.5 mV in an acidic solution and 175.6 mV in an alkaline solution. It also demonstrates exceptional durability, superior to commercial platinum/carbon catalysts. This work introduces a promising approach for designing low-cost, high-performance HER electrocatalysts with a wide pH range.

Enhancement and inactivation effect of CRISPR/Cas12a via extending hairpin activators for detection of transcription factors

An enhancement effect for the activation of CRISPR/Cas12a (CRISPR = clustered regularly interspaced short palindromic repeats; Cas = CRISPR-associated) was discovered. That was, a hairpin model with dangling 5' end complementary to crRNA (CRISPR RNA) greatly improved the activity of CRISPR/Cas12a after extention of two random sequences. But, the corresponding intact hairpin without PAM (protospacer adjacent motif) or suboptimal PAM sequences was completely inactive to CRISPR/Cas12a because of the superhigh stability of intact hairpin. According to the finding, a CRISPR/Cas12a-based strategy coupled with a signal reported system was designed for transcription factors detection. By using mono-labeled ssDNA (single-stranded DNA) as reporter and two newly synthesized N-C (nitrogen-doped carbon) nanosheets as scavenger to eliminate the fluorescent background, the strategy realized the detection of NF-ĸB p50 (p50 subunit of nuclear factor kappa-B) with a linear detection range of 0.8 - 2000.0 pM and a LOD of 0.5 pM. The discovery of "enhancement and inactivation effect" not only deepened insight into CRISPR/Cas12a but also broadened the practical application of CRISPR/Cas systems for the molecular detection and disease diagnostics.

Fe-Ni dual-single atoms nanozyme with high peroxidase-like activity for sensitive colorimetric and fluorometric dual-mode detection of cholesterol

Cholesterol is widely existed in nerve myelin sheath and various membrane structures, whose abnormal level would deteriorate human cells or even cause diseases. Herein, Fe-Ni dual-single-atom nanozyme was efficiently incorporated into N-doped carbon nanosheets (FeNi DSAs/N-CSs) by a simple calcination method. Its nanozyme activity and catalytic mechanism were investigated in details. The FeNi DSAs/N-CSs nanozyme showed superior peroxidase-like property, which was applied for the dual-mode determination of hydrogen peroxide (H2O2) and cholesterol. The colorimetric/fluorometric assays of H2O2 displayed the linear ranges of 1-50 mM and 5-40 mM with low limits of detection of 0.45 mM and 3.33 mM, respectively. In parallel, there exhibited the linear ranges of 0.5-5.0 mM and 0.25-5.0 mM for the colorimetric/fluorometric analysis of cholesterol, coupled with the limits of detection down to 0.19 mM and 0.044 mM, respectively. This work provided a rapid, cost-effectiveness and simple colorimetric/fluorometric method for sensitive dual-mode detection of cholesterol in human serum samples.

Ir-Doped Bilayer Heterojunction Hollow Nanoboxes for Electrocatalytic Oxygen Evolution

The fabrication of hollow nanoelectrocatalysts with multilayered heterogeneous interfaces, derived from metal-organic framework (MOF) materials, represents a highly efficient strategy that promotes the oxygen evolution reaction (OER). Within this research, we successfully synthesized a hollow nanobox of Ir-doped ZIF-67@CoFe PBA with bilayer heterointerfaces. The distinctive structure of Ir-ZIF-67@CoFe PBA provides a substantial number of active sites for reaction intermediates, resulting in improved utilization of precious metals. Furthermore, experimental results indicate the outstanding electrocatalytic performance of the optimized Ir-ZIF-67@CoFe PBA, as indicated by a mere 269 mV overpotential at 10 mA·cm-2, accompanied by a small Tafel slope of 80.1 mV·dec-1. Moreover, the Schottky junction formed between the heterojunction and Ir within Ir-ZIF-67@CoFe PBA accelerates the electron-transfer rate, contributing to its exceptional catalytic performance compared to that of a catalyst derived solely from ZIF-67. This distinctive feature of the catalyst holds tremendous application value.

Novel synergistically effects of palladium-iron bimetal and manganese carbonate carrier for catalytic oxidation of formaldehyde at room temperature

The elimination of formaldehyde at room temperature holds immense potential for various applications, and the incorporation of a catalyst rich in surface hydroxyl groups and oxygen significantly enhances its catalytic activity towards formaldehyde oxidation. By employing a coprecipitation method, we successfully achieved a palladium domain confined within the manganese carbonate lattice and doped with iron. This synergistic effect between highly dispersed palladium and iron greatly amplifies the concentration of surface hydroxyl groups and oxygen on the catalyst, thereby enabling complete oxidation of formaldehyde at ambient conditions. The proposed method facilitates the formation of domain-limited palladium within the MnCO3 lattice, thereby enhancing the dispersion of palladium and facilitating its partial incorporation into the MnCO3 lattice. Consequently, this approach promotes increased exposure of active sites and enhances the catalyst's capacity for oxygen activation. The co-doping of iron effectively splits the doping sites of palladium to further enhance its dispersion, while simultaneously modifying the electronic modification of the catalyst to alter formaldehyde's adsorption strength on it. Manganese carbonate exhibits superior adsorption capability for activated surface hydroxyl groups due to the presence of carbonate. In situ infrared testing revealed that dioxymethylene and formate are primary products resulting from catalytic oxidation of formaldehyde, with catalyst surface oxygen and hydroxyl groups playing a crucial role in intermediate product decomposition and oxidation. This study provides novel insights for designing palladium-based catalysts.

Interface engineering induced charge rearrangement boosting reversible oxygen electrocatalysis activity of heterogeneous FeCo-MnO@N-doped carbon nanobox

The advancement of bifunctional oxygen catalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is imperative yet challenging for the optimization of Zn-air batteries. In this study, we reported the successful incorporation of a novel Mott-Schottky catalytic site within a MnO-FeCo heterojunction into an N-doping carbon nanobox, taking into consideration the effects of the intrinsic electric field and hollow/porous support carriers for electrocatalyst design. As expected, the resulting heterogeneous catalyst exhibited an encouraging half-wave potential of 0.88 V and an impressive limiting-current density of 5.62 mA/cm2 for the ORR, as well as a minimal overpotential of 271 mV at 10 mA/cm2 for the OER, both in alkaline conditions. Furthermore, the Zn-air battery constructed with the heterojunction nanobox product displayed a decent potential gap of 0.621 V, an outstanding power density of 253 mW/cm2, a considerable specific capacity of 761 mAh/gZn, and exceptional stability, with up to 336 h of cycling charging and discharging operation. Consequently, this method of modulating the catalyst's surface charge distribution through an internal electric field at the interface and facilitating mass transport offers a novel avenue for the development of robust bifunctional oxygen catalysts.

Confined synthesis of ternary FeCoMn single-atom nanozyme in N-doped hollow mesoporous carbon nanospheres for synergistic chemotherapy and chemodynamic cancer therapy

Recently, nanozymes show increasing biological applications and promising possibilities for therapeutic intervention, while their mediated therapeutic outcomes are severely compromised due to their insufficient catalytic activity and specificity. Herein, ternary FeCoMn single atoms were incorporated into N-doped hollow mesoporous carbon nanospheres by in situ confinement pyrolysis at 800 °C as high-efficiency nanozyme. The confinement strategy endows the as-prepared nanozyme with the enhanced catalase- and oxidase-like activities. Specifically, the FeCoMn TSAs/N-HCSs nanozyme can decompose intracellular H2O2 to generate O2 and subsequently convert O2 to cytotoxic superoxide radicals (O2∙-), which can initiate cascade enzymatic reactions in tumor microenvironment (TME) for chemodynamic therapy (CDT). Moreover, the cancer therapy was largely enhanced by loading with doxorubicin (DOX). Impressively, the FeCoMn TSAs/N-HCSs nanozyme-mediated CDT and the DOX-induced chemotherapy endow the DOX@FeCoMn TSAs/N-HCSs with effective tumor inhibition, showing the superior therapeutic efficacy.

Integrating PtCo nanoparticles on N, S doped pore carbon nanosheets as high-performance bifunctional catalysts for oxygen reduction and hydrogen evolution reactions

The development of low-Pt bifunctional electrocatalysts with excellent performance for oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER) is critical for the advancement of the hydrogen economy. Here, we have integrated low-loading Pt and Co metals into N, S doped porous carbon nanosheets to obtain composite catalysts encapsulating PtCo alloy nanoparticles (PtCo2@Co9S8/N-CNS and PtCo2@N-CNS). The acquired PtCo nanoparticles, with dimensions of about 2.5 nm, are uniformly distributed and firmly anchored in N, S doped carbon nanosheets with large specific surface areas and rich pore structure, forming multiple active centers and effectively preventing the aggregation of metal nanoparticles. The PtCo2@Co9S8/N-CNS and PtCo2@N-CNS display high ORR catalytic mass activity of 1.65 A mgPt-1 and 1.01 A mgPt-1 in 0.1 M HClO4. The PtCo2@N-CNS catalyst exhibits excellent HER performance in 0.5 M H2SO4, with a mass activity (at 50 mV) 4.3 times higher than that of Pt/C. The PtCo2@Co9S8/N-CNS and PtCo2@N-CNS also exhibit stronger ORR and HER stability than Pt/C after accelerated durability tests. The superior catalytic activity performance of catalysts can be attributed to the synergistic effect of multiple active centers of PtCo, Co9S8 and Co-N in the catalysts. The confinement of PtCo nanoparticles by Co metal and N, S doped porous nanosheets derived from graphitic carbon nitride (g-C3N4) as the template, which can effectively prevent the corrosion and migration of the catalysts under acidic conditions, enhances the catalytic stability of the materials. This study provides a new perspective for the development of economical and efficient bifunctional low-Pt catalysts.

Nanozyme-assisted ratiometric photoelectrochemical aptasensor over Cu2O nanocubes mediated photocurrent-polarity-switching based on S-scheme FeCdS@FeIn2S4 heterostructure

The controllable modulation of the response mode is highly attractive for the construction of photoelectrochemical (PEC) sensors with improved sensitivity and anti-interference ability in complex real samples matrix. Here, we present a charming proof-of-concept ratiometric PEC aptasensor of enrofloxacin (ENR) analysis via the controllable signal transduction. Different with the traditional sensing mechanism, this ratiometric PEC aptasensor integrates the anodic PEC signal induced by PtCuCo nanozyme-catalyzed precipitation reaction and the polarity-switching cathodic PEC response mediated by Cu2O nanocubes on S-scheme FeCdS@FeIn2S4 heterostructure. Taking advantages of the photocurrent-polarity-switching signal response model and the superior performance of the photoactive substrate material, the proposed ratiometric PEC aptasensor displays a good detection linear range for ENR analysis from 0.01 pg mL-1 to 10 ng mL-1, with a detection limit of 3.3 fg mL-1. This study provides a general platform for detecting interested trace analytes in real samples and expands the diversity of sensing strategy design.

A three-dimensional composite film-modified electrode based on polyoxometalates and ionic liquid-decorated carbon nanotubes for the determination of L-tyrosine in food

A stable and innovative composite film-modified electrode based on Dawson polyoxometalates H8P2Mo16V2O62 (P2Mo16V2) and ionic liquid (BMIMBr)-decorated carbon nanotubes, annotated as PEI/(P2Mo16V2/BMIMBr-CNTs)8, has been constructed by using the layer-by-layer self-assembly (LBL) method for the determination of L-tyrosine. The combination of three active components not only offers higher conductivity to facilitate rapid electron transfer, but also avoids the accumulation of P2Mo16V2 to expand the contact area and increase the reactive active sites. The modified electrode exhibits outstanding sensing performance for determination of Tyr with wide linear determination range of 5.8×10-7 M ~ 1.2×10-4 M, low determination limit of 1.7×10-7M (S/N=3), high selectivity for common interferences, and excellent stability at the potential of +0.78 V (vs. Ag/AgCl (3 M KCl)). The relative standard deviation (RSD) of 4.3% for five groups of parallel experiments shows the satisfactory repeatability of PEI/(P2Mo16V2/BMIMBr-CNTs)8. In addition, for determination of Tyr, the PEI/(P2Mo16V2/BMIMBr-CNTs)8 shows good recoveries of 98.8-99.8% in meat floss, which can be feasible in practical application.

Acid Etching Strategy: Optimizing Bifunctional Activities of Metal/Nitrogen-doped Carbon Catalysts for Efficient Rechargeable Zn-Air Batteries

Transition metal-embedded heteroatom carbon composites are regarded as an important branch of bifunctional catalysts for rechargeable Zn-air batteries. The inevitable transition metal particles on the carbon skeleton may affect the availability of the metal-heteroatom-carbon catalytic site. Herein, we propose an acid treatment strategy to remove the bare transition metal particles, thus regulating the electrochemical surface area. The OER activities are highly related to the electrochemical surface area for the catalysts with different acid treatment times. In addition, there exists an optimal acid treatment time to achieve the highest ORR and OER activities with the ΔE value of 0.75 V. Given the superior bifunctional activities after acid treatment, we further assemble the rechargeable Zn-air batteries with the optimal catalyst, which achieves a peak power density of 364 mW cm-2 and long cycling life of 500 h at 10 mA cm-2 . This work affords an efficient strategy to enhance the ORR/OER activities and may guide the design of transition metal/heteroatom carbon composites.

One-pot wet-chemical fabrication of 3D urchin-like core-shell Au@PdCu nanocrystals for electrochemical breast cancer immunoassay

Carbohydrate antigen 15-3 (CA15-3) is an important biomarker for early diagnosis of breast cancer. Herein, a label-free electrochemical immunosensor was built based on three-dimensional (3D) urchin-like core-shell Au@PdCu nanocrystals (labeled Au@PdCu NCs) for highly sensitive detection of CA15-3, where K3[Fe(CN)6] behaved as an electroactive probe. The Au@PdCu NCs were synthesized by a simple one-pot wet-chemical approach and the morphology, structures, and electrocatalytic property were investigated by several techniques. The Au@PdCu NCs prepared worked as electrode material to anchor more antibodies and as signal magnification material by virtue of its exceptional catalytic property. The developed biosensor exhibited a wide linear detection range from 0.1 to 300 U mL-1 and a low limit of detection (0.011 U mL-1, S/N = 3) for determination of CA15-3 under the optimal conditions. The established biosensing platform exhibits some insights for detecting other tumor biomarkers in clinical assays and early diagnosis.

Cu2+-regulated one-pot wet-chemical synthesis of uniform PdCu nanostars for electrocatalytic oxidation of ethylene glycol and glycerol

The fabrication of effective and stable electrocatalysts is crucial for practical applications of direct alcohol fuel cells (DAFCs). In this study, bimetallic PdCu nanostars (PdCu NSs) were fabricated by a Cu²⁺-modulated one-pot wet-chemical method, where cetyltrimethyl ammonium bromide (CTAB) worked as a structure-regulating reagent. The morphology, compositions, crystal structures and formation mechanism of the as-prepared PdCu NSs were investigated by a series of techniques. The unique architectures created abundant active sites, which resulted in a large electrochemical active surface area (9.5 m² g^-1). The PdCu NSs showed negative shifts in the onset potentials and large forward peak current densities by contrast with those of commercial Pd black for the catalytic ethylene glycol oxidation reaction (EGOR) and glycerol oxidation reaction (GOR). It revealed that the PdCu NSs outperformed Pd black in the similar surroundings. This work provides a constructive strategy for fabrication of high-efficiency electrocatalysts for alcohol fuel cells.

Noble-metal-free co-N-C catalyst derived from cellulose-based poly(ionic liquid)s for highly efficient oxygen reduction reaction

Noble-Metal-Free nitrogen-doped carbon-based materials are promising electrocatalysts for oxygen reduction reaction (ORR), yet it remains a great challenge to construct efficient porous non-noble metal nitrogen-doped carbon (M-N-C) catalysts with uniform distribution, due to the easy aggregation of metals. Herein, we reported the synthesis and assessment of a novel and efficient noble-metal-free catalyst for oxygen reduction reaction (ORR) from pyrolysis of a cobalt-containing cellulosic poly(ionic liquid) (Co-N-C). The prepared Co-N-C catalyst possesses high surface area, hierarchical porous structure, well-dispersed Co nanoparticles and large amounts of low-coordinated Co active sites. Especially, the Co-N-C-850 sample exhibits a high ORR activity (E_onset = 0.827 V, E_1/2 = 0.74 V) that can rival 20 wt% commercial Pt/C (E_onset = 0.833 V, E_1/2 = 0.71 V) in alkaline media. Moreover, the Co-N-C-850 sample also shows excellent anti-methanol poisoning activity and long-term stability toward ORR compared with commercial Pt/C. Our study provides a promising avenue both for the development of non-noble M-N-C catalysts for fuel cells and functional utilization of cellulose.

Hollow cage-like PtCu nanozyme-regulated photo-activity of porous CdIn2S4/SnO2 heterojunctions for ultrasensitive PEC sensing of streptomycin

Streptomycin (STR) is extensively employed for preventive and curative purposes in animals, which is accumulated in human body through food chain and induces serious health problems. Herein, highly photoactive type II heterojunctions of porous CdIn₂S₄/SnO₂ microspheres were initially prepared, which can effectively inhibit the recombination of the charge-hole pairs. Besides, the peroxidase-mimicking catalytic property of the hollow PtCu nanocages (PtCu NCs) was carefully investigated by UV-vis spectroscopy, where catalytic oxidation of tetramethylbenzidine behaved as the benchmarked reaction. On such basis, a highly selective photoelectrochemical (PEC) aptasensor was established with the CdIn₂S₄/SnO₂ heterojunctions for bioanalysis of streptomycin, coupled by the PtCu NCs nanozyme-catalyzed biocatalytic precipitation to achieve signal magnification. Specifically, the home-made nanozyme was applied for catalytic oxidation of 3,3'-diaminobenzidine to generate insulating precipitate in aqueous H₂O₂ system and thereby block the light harvesting on the photoanode, showing steeply declined PEC responses. The as-built aptasensor showed a broad linear range of 0.01-200 nM with a low limit of detection of 7.50 pM (S/N = 3) for such analysis, combined by exploring its practical detection in milk samples. This work shows excellent nanozyme-catalyzed signal amplification for fabrication of ultrasensitive PEC biosensors towards other antibiotics detection.

Mulberry-like porous-hollow AuPtAg nanorods for electrochemical immunosensing of biomarker myoglobin

Mulberry-like AuPtAg porous hollow nanorods (PHNR) were facilely synthesized for the first time via a wet chemical method, where Au nanorods (Au NR) behaved as sacrificed template. The anisotropic oriented growth and etching process are involved in this synthesis. Their structural and electronic characteristics were scrutinously examined by TEM, EDS, XPS, and electrochemical techniques. The AuPtAg PHNR provided a large specific surface area and exposed a large number of active sites, showing highly enhanced catalytic activity. On this foundation, a label-free electrochemical immunosensor was developed for myoglobin (Myo) assay based on the AuPtAg PHNR. Further, the built sensor exhibited fast and ultrasensitive responses in a linear range of 0.0001 ~ 1000 ng mL^-1 with a low limit of detection (LOD = 0.46 pg mL^-1, S/N = 3), and enabled efficient application to human serum samples with acceptable results. Consequently, the developed AuPtAg PHNR-based platform has a broad prospect in practically monitoring Myo and other biomarkers in clinics.

Lignin-derived iron carbide/Mn, N, S-codoped carbon nanotubes as a high-efficiency catalyst for synergistically enhanced oxygen reduction reaction and rechargeable zinc-air battery

Design of efficient and durable oxygen reduction reaction (ORR) electrocatalysts still remains challenge in sustainable energy storage and conversion devices. To achieve sustainable development, it is of importance to prepare high-quality carbon-derived ORR catalysts from biomass. Herein, Fe₅C₂ nanoparticles (NPs) were facilely entrapped in Mn, N, S-codoped carbon nanotubes (Fe₅C₂/Mn, N, S-CNTs) by a one-step pyrolysis of the mixed lignin, metal precursors and dicyandiamide. The resulting Fe₅C₂/Mn, N, S-CNTs had open and tubular structures, which exhibited positive shifts in the onset potential (E_onset = 1.04 V) and high half-wave potential (E_1/2 = 0.85 V), showing excellent ORR characteristics. Further, the typical catalyst-assembled Zn-air battery showed a high power density (153.19 mW cm^-2) and good cycling performance as well as obvious cost advantage. The research provides some valuable insights for rational construction of low-cost and environmentally sustainable ORR catalysts in clean energy field, coupled by offering some valuable insights for reusing biomass wastes.