Cobalt nanoparticles/ nitrogen, sulfur-codoped ultrathin carbon nanotubes derived from metal organic frameworks as high-efficiency electrocatalyst for robust rechargeable zinc-air battery

Signal amplification strategy based on target-controlled release of mediator for ultrasensitive self-powered biosensing of acetamiprid

Self-powered biosensors with high sensitivity have garnered significant interest for their potential applications in the realm of portable sensing. Herein, a self-powered biosensor with a novel signal amplification strategy was developed by integrating target-controlled release of mediator with an enzyme biofuel cell for the ultrasensitive detection of acetamiprid (ACE). Zeolitic imidazolate framework-67 was utilized as both a nanocontainer for capturing the electron mediator 2,2'-azidobis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), and a precursor for the synthesis of cobalt nanoparticles/nitrogen, sulfur-codoped carbon nanotubes (Co NPs/NS-CNTs), which were employed as the electrode material for constructing both the glucose oxidase-based bioanode and the laccase-based biocathode. The target analyte ACE can specifically bind to its aptamer, leading to the release of ABTS, which cyclically participates in the catalytic reaction of the biocathode, thereby amplifying the electrochemical signal. By leveraging the benefits of ABTS cyclic catalysis and the effective electrocatalysis of bioelectrodes based on Co NPs/NS-CNTs, the self-powered biosensor has a broad detection range of 0.1-1000 fM and a low detection limit of 25 aM toward ACE. The proposed signal amplification approach presents a promising strategy for enhancing sensitivity and enabling portable analysis in applications of food safety, environmental monitoring, and medical diagnostics.

Exceptionally Bifunctional ORR/OER Performance via Synergistic Atom-Cluster Interaction

The single-atom sites (SAs) have achieved enhanced performance toward oxygen reduction reaction (ORR) with the effective utilization of the active sites. However, the excess adsorption of the intermediates and the limited stability hinders performance improvement. Metal clusters with promising stability and weak adsorption can be used as potential substitutions, but the lack of active sites is considered undesirable for catalytic reactions. Herein, a framework of Fe nanoclusters combined with SAs on One dimensional (1D) carbon nanotubes (Fe3C-NCNTs 90 min CC-1) is synthesized to confirm the synergistic atom-cluster interaction. The composite exhibits strong polarization and electron redistribution between nanocluster and SAs. The electron redistribution will significantly boost the electron transport and the desorption of the intermediates, which is confirmed by off-axis holography and DFT calculation. The electrocatalytic performance is significantly enhanced as the half-wave potential of ORR increased 75 mV and the potential of OER increased 133 mV compared with the sample without nanoclusters. Furthermore, such a bifunctional catalyst endows homemade Zn-air batteries (ZABs) with high power density and long-term stability. This work paves a facile route to design bifunctional ORR/OER electrocatalysts consisting of 0D composite structures.

Removal and reuse of heavy metal ions on mildly oxidized Ti3C2 @BF membrane via synergistic photocatalytic-photothermal approach

The pollution of heavy metal ions in water seriously affects the ecosystem and human health. Here, an efficient synergetic photocatalytic-photothermal system is designed by combining a mildly oxidized Ti3C2 (mo-Ti3C2) with a super hydrophilic bamboo fiber (BF) membrane. The mo-Ti3C2 heterojunction promotes the transfer and separation of photoinduced charges and thus enhances the photocatalytic reduction of heavy metal ions (Co2+, Pb2+, Zn2+, Mn2+ and Cu2+). The photoreduced metal nanoparticles with high conductivity and LSPR effect further accelerate the transfer and separation of photoinduced charges, and improve photothermal and evaporative performance. The mo-Ti3C2-2.4 @BF membrane in Co(NO3)2 solution can achieve an excellent evaporation rate of 4.6 kg·m-2·h-1 and a high solar-vapor efficiency of up to 97.5% under the light intensity of 2.44 kW·m-2, which are 27.8% and 19.6% higher than those in H2O, respectively, demonstrating the reuse of photoreduced Co nanoparticles. No heavy metal ions are detected in any of the condensed water, and the Co2+ removal rate in the concentrated Co(NO3)2 solution is up to 80.4%. The synergetic photocatalytic-photothermal approach on the mo-Ti3C2 @BF membrane provides a new scope for the continuous removal and reuse of heavy metal ions, as well as for obtaining clean water.

N-Doped Carbon Nanotubes Supported Fe-Mn Dual-Single-Atoms Nanozyme with Synergistically Enhanced Peroxidase Activity for Sensitive Colorimetric Detection of Acetylcholinesterase and Its Inhibitor

Monitoring acetylcholinesterase (AChE) and its inhibitors is of importance for early diagnosis and therapy of neurological diseases. Herein, N-doped carbon nanotubes supported Fe-Mn dual-single-atoms (FeMn DSAs/N-CNTs) were fabricated by a simple pyrolysis, as thoroughly figured out by a series of the characterization techniques. The peroxidase-like activity of FeMn DSAs/N-CNTs was investigated by catalytic oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) to generate rich hydroxyl radicals (·OH) in the H₂O₂ system, which effectively catalyzed colorless TMB oxidation to blue oxidized TMB (ox-TMB). Besides, the peroxidase-like activity was greatly weakened by thiocholine (derived from AChE), accompanied by making blue ox-TMB fade. Impressively, the highly improved peroxidase-like property is further evidenced by density functional theory (DFT) calculations, where the dual-single atoms show a lower energy barrier (0.079 eV) and their interactions with the N-CNTs played critical roles for producing the oxygen radicals. By virtue of the nanozyme, a low-cost, specific, and sensitive colorimetric sensor was built for detection of AChE with a broader linear range of 0.1-30 U L^-1 and a lower limit of detection (LOD, 0.066 U L^-1), combined with its feasible analysis in human serum samples. Also, this platform was applied for measuring huperzine A inhibitor with a wide linear scope of 5-500 nM and a LOD down to 4.17 nM. This strategy provides a low-cost and convenient approach for early clinical diagnosis and drug development.

High-Activity Fe3 C as pH-Universal Electrocatalyst for Boosting Oxygen Reduction Reaction and Zinc-Air Battery

Transition metal catalysts are regarded as one of promising alternatives to replace traditional Pt-based catalysts for oxygen reduction reaction (ORR). In this work, an efficient ORR catalyst is synthesized by confining Fe₃ C nanoparticles into N, S co-doped porous carbon nanosheets (Fe₃ C/N,S-CNS) via high-temperature pyrolysis, in which 5-sulfosalicylic acid (SSA) demonstrates as an ideal complexing agent for iron (ΙΙΙ) acetylacetonate while g-C₃ N₄ behaves as a nitrogen source. The influence of the pyrolysis temperature on the ORR performance is strictly examined in the controlled experiments. The obtained catalyst exhibits excellent ORR performance (E_1/2  = 0.86 V; E_onset  = 0.98 V) in alkaline electrolyte, coupled by exhibiting the superior catalytic activity and stability (E_1/2  = 0.83 V, E_onset  = 0.95 V) to Pt/C in acidic media. In parallel, its ORR mechanism is carefully illustrated by the density functional theory (DFT) calculations, especially the role of the incorporated Fe₃ C played in the catalytic process. The catalyst-assembled Zn-air battery also exhibits a much higher power density (163 mW cm^-2 ) and ultralong cyclic stability in the charge-discharge test for 750 h with a gap increase down to 20 mV. This study provides some constructive insights for preparation of advanced ORR catalysts in green energy conversion units correlated systems.

One-Step Synthesis of a Non-Precious-Metal Tris (Fe/N/F)-Doped Carbon Catalyst for Oxygen Reduction Reactions

Advancements in inexpensive, efficient, and durable oxygen reduction catalysts is important for maintaining the sustainable development of fuel cells. Although doping carbon materials with transition metals or heteroatomic doping is inexpensive and enhances the electrocatalytic performance of the catalyst, because the charge distribution on its surface is adjusted, the development of a simple method for the synthesis of doped carbon materials remains challenging. Here, a non-precious-metal tris (Fe/N/F)-doped particulate porous carbon material (2₁P₂-Fe₁-850) was synthesized by employing a one-step process, using 2-methylimidazole, polytetrafluoroethylene, and FeCl₃ as raw materials. The synthesized catalyst exhibited a good oxygen reduction reaction performance with a half-wave potential of 0.85 V in an alkaline medium (compared with 0.84 V of commercial Pt/C). Moreover, it had better stability and methanol resistance than Pt/C. This was mainly attributed to the effect of the tris (Fe/N/F)-doped carbon material on the morphology and chemical composition of the catalyst, thereby enhancing the catalyst's oxygen reduction reaction properties. This work provides a versatile method for the gentle and rapid synthesis of highly electronegative heteroatoms and transition metal co-doped carbon materials.

Three-dimensional self-supporting superstructured double-sided nanoneedles arrays of iron carbide nanoclusters embedded in manganese, nitrogen co-doped carbon for highly efficient oxygen reduction reaction

Nitrogen- and transition metal-dual doped carbon materials with low cost and high catalytic performances are considered as one of promising alternatives for noble metal catalysts in acceleration of oxygen reduction reaction (ORR). In this work, three-dimensional (3D) self-supporting superstructures of iron carbide (Fe₃C) nanoclusters entrapped in manganese (Mn)- and nitrogen (N)-dual doped carbon nanosheets covered with double-sided nanoneedles carbon arrays (Fe₃C/Mn,N-NCAs) are simply synthesized by a coordination pyrolysis method, in which dicyandiamide mainly behaves as nitrogen source and 1-(2-pyridylazo)-2-naphthol (PAN) as carbon source. Integration of the unique 3D self-supporting superstructures and synergistic effects of the multi-compositions, the as-obtained catalyst displays appealing ORR performance such as the much positive onset potential (E_onset = 0.98 V vs. RHE) and half-wave potential (E_1/2 = 0.88 V vs. RHE), as well as a just 10 mV negative shift in E_1/2 after 2000 cycles, surpassing commercial Pt/C. This work provides some valuable perspectives for preparation of high-efficiency and low-cost non-noble metal ORR electrocatalysts in energy transformation and storage correlated systems.

Ru-incorporated Co3O4 nanoparticles from self-sacrificial ZIF-67 template as efficient bifunctional electrocatalysts for rechargeable metal-air battery

Ru-incorporated Co₃O₄ nanoparticles have been synthesized from self-sacrificial ZIF-67 template and utilized as efficient electrocatalysts towards oxygen reduction and evolution reactions (ORR and OER). Amongst, Ru@Co₃O₄-1.0 exhibited the optimum electrocatalytic behavior with an ultra-low potential gap (0.84 V) between the OER potential (1.61 V at 10 mA cm^-2) and ORR half-wave potential (0.77 V). The zinc-air battery using Ru@Co₃O₄-1.0 as a cathode presented high specific capacity (788.1 mAh g^-1) and power density (101.2 mW cm^-2). Meanwhile, this battery possessed relatively lower voltage gap and higher cycling stability compared with the commercial Pt/C-based one. Ruthenium incorporation induced remarkable lattice expansion of Co₃O₄ and engineered more oxygen vacancies, promoting the lattice oxygen mobility from the subsurface/bulk phase onto surface. All these properties were recognized to be the crucial parameters for electrocatalytic activity improvement. This work provided a facile approach to design highly active metal oxide with broad potentiality for rechargeable metal-air batteries.

High-pressure vapor-solid transformation of 2D template to derive 2D Co-N-C electrocatalysts for oxygen reduction reaction

Two-dimensional (2D) cobalt zeolitic imidazolate frameworks (ZIF-67) have attracted significant research interests to synthesize cobalt and nitrogen co-doped carbon-based (Co-N-C) catalyst for oxygen reduction reaction (ORR). However, most of the current synthetic approaches of 2D ZIF-67 are energy-intensive, environmentally hazardous and low-yield. Herein, a feasible and efficient 'morphology-retaining method via a high-pressure vapor-solid reaction' are reported to synthesize 2D ZIF-67 nanosheets by using 2D cobalt carbonate hydroxide template. In the strategy, the high-pressure vapor caused by sublimation of 2-Melm and the pores formed from effusion of CO₂during transformation ensure the complete transformation from 2D template to 2D ZIF-67. The corresponding 2D Co-N-C catalyst exhibits comparable ORR electrocatalytic activity and better stability than Pt/C in alkaline media. The present method is expected to offer a feasible and universal way to efficiently synthesize 2D M-N-C catalysts.

Large-scale defect-rich iron/nitrogen co-doped graphene-based materials as the excellent bifunctional electrocatalyst for liquid and flexible all-solid-state zinc-air batteries

Defect-engineering in transition-metal-doped carbon-based catalyst plays an essential role for improving the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) performance. Herein, we report a ball-milling induced defect assisted with ZnCl₂ strategy for fabricating defect-rich iron/nitrogen co-doped graphene-based materials (Fe-N-G). The substantial mechanical shear forces and the constant corrosion to the carbon matrix by ZnCl₂ lead to the creation of abundant defects in graphene-based materials, which facilitates doping for heteroatoms. The defect-rich Fe-N-G catalyst with abundant Fe-N_x active sites displays excellent ORR performance. For OER, the over potential for Fe-N-G outperforms that of RuO₂ in 1 M KOH at 10 mA cm^-2. The Density Functional Theory calculations unravel that the impressive OER performance is attributable to the introduction of abundant defects. Additionally, the liquid and all-solid-state zinc-air batteries equipped with the prepared material as the air cathode demonstrate high power density, high specific capacity, and long charge-discharge stability. This work offers a practical method for manufacturing high-performance electrocatalysts for environmental and energy-related fields.