Accelerating Proton and Electron Transfer Enables Highly Active Fe─N─C Catalyst for Electrochemical CO2 Reduction

Atomically dispersed Fe─N─C catalysts display great potential for efficient CO production in the field of electrochemical CO₂ reduction (ECR), but still suffer from unsatisfactory activity limited by the slow proton and electron transfer during the ECR process. Here, a superior Fe─N─C electrocatalyst is designed by anchoring the individual FeN₄ sites and Fe nanoparticles onto highly conductive carbon nanotubes. The resultant catalyst displays a commendable CO partial current density of 16.01 mA cm⁻² with a turnover frequency of 3519.6 h⁻¹ at −0.65 V in an H-type cell, and also exhibits CO selectivity > 90% under high current density over 120 mA cm⁻² in a flow cell. This remarkable activity exceeds a host of previously reported Fe─N─C catalysts. The findings indicate that the carbon nanotube facilitates CO production due to its strong capability of electron transport and charge transfer. In situ spectroscopic analysis, controlled experiments, and theoretical calculations reveal that Fe nanoparticles effectively promote water dissociation and the subsequent protonation step, accelerate the formation of ^*COOH intermediate, and thus greatly enhance the ECR activity.     

Highly Reversible Zinc-Air Batteries at −40 °C Enabled by Anion-Mediated Biomimetic Fat

The wide application of portable electrical equipment, aerial vehicles, smart robotics, etc. has boosted the development of advanced batteries with safety, high energy density, and environmental adaptability. Inspired by the fat layer on animal bodies, biomimetic fat is constructed as electrolytes of solid-state zinc-air batteries to achieve excellent cycling performance at low temperatures. Via tailored anion-H₂O interaction, the antifreezing gel electrolytes, with the multi-performance of interface compatibility, temperature adaptability, and stable power supply simultaneously, build robust Zn|electrolyte interface, thus promoting uniform interfacial electric fields and Zn deposition. Excellent long-term cyclability of 120 h at a high current density of 50 mA cm⁻² are exhibited at 25 °C. Moreover, at −40 °C, a record-long cycling life of 205 h at a current density as large as 10 mA cm⁻² is achieved.     

Electrochemical C——V Characteristics and Photoluminescence of a—C ： N Films

Amorphous carbon (a—C) films and amorphous carbon films incorporating with the nitrogen (a-C : N) were deposited on silicon substrates in a radio-frequency driven plasma enhanced chemical vapour deposition system, while the surface electrical properties of films were investigated by electrochemical capacitance-voltage measurements. It was examined the effect of the interface defects on the properties and deduced that the conducting type of a--C : N films was n--type. Subsequently, a comparative studies of a--C and a- C : N films were performed by photoluminescence spectra depending on the temperature. With the decrease of the temperature, the main band with peak energy of 2.48 eV in the a-C：N films was more intense compared with the other three bands caused by amorphous C in the a-C films.     

Fe─N─C Electrocatalyst for Enhancing Fe(II)/Fe(III) Redox Kinetics in Thermo-Electrochemical Cells

Harvesting low-grade waste heat, which constitutes 60% of the overall waste heat, is key to halting climate change. Electrochemical waste-heat harvesting has recently drawn attention to practical low-grade waste-heat harvesting. In this study, a power density maximization strategy is presented in scalable and cost-effective aqueous redox couple-based thermo-electrochemical cells (TECs). The n-type feature of the water-soluble Fe^2+/3+ redox couple is essential for constructing the TEC p–n leg device; however, it has not been investigated much so far. The modulation of the chaotropicity of counteranions enhances the absolute value of the Seebeck coefficient for the Fe^2+/3+ redox couple with an inner-sphere reaction mechanism because of the greater structural disorder in the solvation shell. Moreover, the use of a cost-effective Fe─N─C electrocatalyst shows redox kinetics and a power density comparable to those of state-of-the-art Pt electrodes, economically compensating for the sluggish charge-transfer kinetics of the inner-sphere redox mechanism. The Fe─N─C -based TEC device exhibits 1.73 W m⁻² of power density at 0.1 $ W⁻¹ of cost per power, which is 1.24% with respect to the Carnot efficiency, exceeding 0.23–0.53% compared to those reported for previous Pt-based TEC devices with the same redox chemistry.     

Ni3N–CeO2 Heterostructure Bifunctional Catalysts for Electrochemical Water Splitting

Developing low-cost and high-efficient bifunctional catalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is greatly significant for water electrolysis. Here, Ni₃N-CeO₂/NF heterostructure is synthesized on the nickel foam, and it exhibits excellent HER and OER performance. As a result, the water electrolyzer based on Ni₃N-CeO₂/NF bifunctional catalyst only needs 1.515 V@10 mA cm⁻², significantly better than that of Pt/C||IrO₂ catalysts. In situ characterizations unveil that CeO₂ plays completely different roles in HER and OER processes. In situ infrared spectroscopy and density functional theory calculations indicate that the introduction of CeO₂ can optimizes the structure of interface water, and the synergistic effect of Ni₃N and CeO₂ improve the HER activity significantly, while the in situ Raman spectra reveal that CeO₂ accelerates the reconstruction of O_V (oxygen vacancy)-rich NiOOH for boosting OER. This study clearly unlocks the different catalytic mechanisms of CeO₂ for boosting the HER and OER activity of Ni₃N for water splitting, which provides the useful guidance for designing the high-performance bifunctional catalysts for water splitting.     

Physical Unclonable Anticounterfeiting Electrodes Enabled by Spontaneously Formed Plasmonic Core–Shell Nanoparticles for Traceable Electronics

Counterfeit electronics are a growing problem for the electronic information industry worldwide, so developing unbreakable security tags is crucial to ensure the trustworthiness and traceability of electronics. Traditional anticounterfeiting and trace solutions rely on reproducible deterministic processes and additional labels, which can still be copied or faked by counterfeiters. Herein, physical unclonable functions enabled by spontaneously formed plasmonic core–shell nanoparticles on electrodes are proposed to ensure label-free traceable electronics, giving a practical solution to fight against counterfeit electronics. Random hemispherical core–shell nanoparticles are intentionally introduced on the metal electrode of different semiconductors (Si, GaAs, and GaN) from Ni/Au bilayer heterofilms by rapid thermal annealing, which can be integrated with electronics seamlessly, with no negative effect on electrical properties. The position, size, and shape of nanoparticles are random and uncontrollable; the corresponding scattering patterns, intensity, and spectra can work as nanofingerprints of the electrode, proving multidimensional unclonable labels with large encoding capacity suitable for electrodes smaller than several micrometers. It can be further combined with machine vision and artificial intelligence to identify and track electronics automatically and efficiently. The anticounterfeiting electrodes also show good thermal robustness and mechanical stability, opening up a prospect for practical anticounterfeiting of electronics.     

High Performing Solid-State Organic Electrochemical Transistors Enabled by Glycolated Polythiophene and Ion-Gel Electrolyte with a Wide Operation Temperature Range from −50 to 110 °C

The development of organic electrochemical transistors (OECTs) capable of maintaining their high amplification, fast transient speed, and operational stability in harsh environments will advance the growth of next-generation wearable and biological electronics. In this study, a high-performance solid-state OECT (SSOECT) is successfully demonstrated, showing a recorded high transconductance of 220 ± 59 S cm⁻¹, ultrafast device speed of ≈10 kHz with excellent operational stability over 10 000 switching cycles, and thermally stable under a wide temperature range from −50 to 110 °C. The developed SSOECTs are successfully used to detect low-amplitude physiological signals, showing a high signal-to-noise-ratio of 32.5 ± 2.1 dB. For the first time, the amplifying power of these SSOECTs is also retained and reliably shown to collect high-quality electrophysiological signals even under harsh temperatures (−50 and 110 °C). The demonstration of high-performing SSOECTs and its application in harsh environment are core steps toward their implementation in next-generation wearable electronics and bioelectronics.     

Regulating the Metallic Cu–Ga Bond by S Vacancy for Improved Photocatalytic CO2 Reduction to C2H4

Artificial photosynthesis, which converts carbon dioxide into hydrocarbon fuels, is a promising strategy to overcome both global warming and energy crisis. Herein, the geometric position of Cu and Ga on ultra-thin CuGaS₂/Ga₂S₃ is oriented via a sulfur defect engineering, and the unprecedented C₂H₄ yield selectivity is ≈93.87% and yield is ≈335.67 µmol g⁻¹ h⁻¹. A highly delocalized electron distribution intensity induced by S vacancy indicates that Cu and Ga adjacent to S vacancy form Cu–Ga metallic bond, which accelerates the photocatalytic reduction of CO₂ to C₂H₄. The stability of the crucial intermediates (*CHOHCO) is attributed to the upshift of the d-band center of ultra-thin CGS/GS. The C–C coupling barrier is intrinsically reduced by the dominant exposed Cu atoms on the 2D ultra-thin CuGaS₂/Ga₂S₃ in the process of photocatalytic CO₂ reduction, which captures *CO molecules effectively. This study proposes a new strategy to design photocatalyst through defect engineering to adjust the selectivity of photocatalytic CO₂ reduction.     

Steering Local Electronic Configuration of Fe–N–C-Based Coupling Catalysts via Ligand Engineering for Efficient Oxygen Electroreduction

Fe–N–C materials are prospective candidates to displace platinum-group-based oxygen reduction reaction (ORR) catalysts, but their application is still impeded by the conundrums of unsatisfactory activity and stability. Herein, a feasible strategy of ligand engineering of the metal-organic framework is proposed to steer the local electronic configuration of Fe–N–C-based coupling catalysts by incorporating engineered sulfur functionalities. The obtained catalysts with rich Fe-N₄ sites and FeS nanoparticles are embedded on N/S-doped carbon (denoted as FeS/FeNSC). In this unique structure, the engineered FeS nanoparticles and oxidized sulfur synergistically induce electron redistribution and modulate electronic configuration of Fe-N₄ sites, contributing to substantially accelerated kinetics and improved activity. Consequently, the optimized FeS/FeNSC catalyst displays outstanding ORR performance with a half-wave potential of 0.91 V, better four electron pathway selectivity, lower H₂O₂ yield, and superior long-term stability. As a proof-of-concept, zinc-air batteries based on FeS/FeNSC deliver high capacity of 807.54 mA h g⁻¹, a remarkable peak power density of 256.06 mW cm⁻², and outstanding cycling stability over 600 h at 20 mA cm⁻². This study delivers an efficacious approach to manipulate the electronic configuration of Fe–N–C catalysts toward elevated catalytic activity and stability for various energy conversion/storage devices.     

High Areal Capacity Dendrite-Free Li Anode Enabled by Metal–Organic Framework-Derived Nanorod Array Modified Carbon Cloth for Solid State Li Metal Batteries

Li metal is one of the most promising anode materials for high energy density batteries. However, uncontrollable Li dendrite growth and infinite volume change during the charge/discharge process lead to safety issues and capacity decay. Herein, a carbonized metal–organic framework (MOF) nanorod arrays modified carbon cloth (NRA-CC) is developed for uniform Li plating/stripping. The carbonized MOF NRAs effectively convert the CC from lithiophobic to lithiophilic, decreasing the polarization and ensuring homogenous Li nucleation. The 3D interconnected hierarchal CC provides adequate Li nucleation sites for reducing the local current density to avoid Li dendrite growth, and broadens internal space for buffering the volume change during Li plating/stripping. These characteristics afford a stable cycling of the NRA-CC electrode with ultrahigh Coulombic efficiencies of 96.7% after 1000 h cycling at 2 mA cm⁻² and a prolonged lifespan of 200 h in the symmetrical cell under ultrahigh areal capacity (12 mAh cm⁻²) and current (12 mA cm⁻²). The solid-state batteries assembled with the composite Li anode, high-voltage cathode (LiNi_0.5Co_0.2Mn_0.3O₂), and composite solid-state electrolyte also deliver excellent cyclic and rate performance at 25 °C. This work sheds fresh insights on the design principles of a dendrite-free Li metal anode for safe solid-state Li metal batteries.     

Optimization of Interfacial OH− Accessibility by Constructing a Delayed–Release Membrane Electrode for Ampere–Level Hydrogen Production

Achieving a high current density during electrochemical overall water splitting is a promising strategy for industrial energy conversion. The mass diffusion rate of OH⁻ ions from the electrolyte to the interfacial active sites strongly influences the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) . Herein, the delayed-release of OH⁻ ions modulated by a proper organic polymer membrane on the electrode surface can optimize the OH⁻ accessibility to the active sites (as indicated by the molecular dynamics simulations) is demonstrated and that van der Waals interaction force modulates the OH⁻ residence time in the reaction system. The remarkable performance of the membrane-modified electrode  is achieved at ultra-high current densities of 1.9 A cm⁻² (with an HER overpotential of 602 mV) and 2 A cm⁻² (with an OER overpotential of 459 mV) in 1 M KOH solution. Consequently, a super-high current density of 1.3 A cm⁻² is obtained for overall water splitting (at a voltage of only 2.2 V), which is 1.9-fold higher than that of a benchmarked Pt/C-IrO₂ (684 mA cm⁻²). Therefore, the delayed-release of OH⁻ has optimized the mass conversion efficiency of the active sites, thus improving the electrochemical performance of overall water splitting.     

TiN @ Co5.47N Composite Material Constructed by Atomic Layer Deposition as Reliable Electrocatalyst for Oxygen Evolution Reaction

An efficient and durable oxygen evolution reaction (OER) electrocatalyst consisting of TiN @ Co_5.47N is constructed by the integration of plasma nitriding and a delicate atomic layer deposition (ALD) Co_xN process. Representative results of comprehensive study are: 1) the material is electrocatalytically active in universal medium. The OER overpotentials are 398, 248, and 411 mV in acidic, basic, and neutral electrolyte, respectively, at a current density of 50 mA cm⁻²; 2) the material records an impressive long-term stability of continuous catalysis for 1500 h, during which the overpotential increases by only 1.3%. The synergistically electronic interaction between TiN and ALD Co_5.47N, as well as a protective yet active CoTi layered double hydroxides (CoTi LDH) layer formed simultaneously at the interface/surface of TiN @ Co_5.47N during the electrocatalytic process, is speculated to be responsible for the superior OER performance; 3) the surface Co atoms other than Ti of CoTi LDH, exhibit electrocatalytic activity with dramatically low overpotential based on density functional theory calculations.     

Consequences of twisting the aromatic core of N,N′-dimethylperylene-3,4,9,10-biscarboximide by chemical substitution for the electronic coupling and electric transport in thin films

Thin films of 1,6,7,12-tetrachloro-N,N^′-dimethylperylene-3,4,9,10-biscarboximide (Cl₄MePTCDI) prepared by physical vapor deposition (PVD) were compared to thin films of the unchlorinated N,N^′-dimethylperylene-3,4,9,10-biscarboximide (MePTCDI) to investigate the influence of a changed molecular structure on the electrical properties of the materials. The films were prepared on microstructured Si/SiO₂ substrates with interdigitated Au electrode arrays of 2 μm electrode distance or on quartz glass with electrode distances in the mm range. The films were investigated by conductance measurements, thermoelectric power, electric field effect, ultraviolet photoelectron spectroscopy (UPS) and atomic force microscopy (AFM). The thickness-dependence of the conductance measured during film growth (in situ) indicated a growth mode in islands (Volmer-Weber), which was confirmed by subsequent AFM. As expected, Cl₄MePTCDI was characterized as an organic n-type semiconductor. Charge transport occurred by a hopping mechanism as revealed by temperature-dependent thermopower and field-effect measurements. Effective electron mobilities at room temperature were found around 10⁻⁵ cm² V ⁻¹ s⁻¹ considerably lower than the values for MePTCDI. A rather constant concentration of mobile electrons of (1–2) × 10¹⁸ cm⁻³ was determined for both materials. The morphology of Cl₄MePTCDI islands indicated amorphous growth as opposed to crystals obtained for MePTCDI, as also revealed earlier by optical spectroscopy and the role of crystallinity in the electrical conduction is discussed.     

Interlayer Spacing Regulation by Single-Atom Indiumδ+–N4 on Carbon Nitride for Boosting CO2/CO Photo-Conversion

Simultaneous optimization on bulk photogenerated-carrier separation and surface atomic arrangement of catalyst is crucial for reactivity of CO₂ photo-reduction. Rare studies capture the detail that, better than in-plane regulation, interlayer-spacing regulation may significantly influence the carrier transport of the bulk-catalyst thereby affecting its CO₂ photo-reduction in g-C₃N₄. Herein, through a single atom-assisted thermal-polymerization process, single-atom In-bonded N-atom (In^δ+–N₄) in the (002) crystal planes of g-C₃N₄ is originally constructed. This In^δ+–N₄ reduces the (002) interplanar spacing of g-C₃N₄ by electrostatic adsorption, which significantly enhances the separation of bulk carriers and greatly promotes the reactivity of CO₂ photoreduction. The CO₂ photo-conversion performance of this resulted single-atom In modified g-C₃N₄ is significantly superior to other single atom loaded carbon nitride catalysts. Moreover, the In^δ+–N₄ enhances the CO₂ adsorption on g-C₃N₄, reduces the *COOH formation energy, and optimizes the reaction path. It achieves a remarkable 398.87 µmol g⁻¹ h⁻¹ yield rate, 0.21% apparent quantum efficiency, and nearly 100% selectivity for CO without any cocatalyst or sacrificial agent. Through d₍₀₀₂₎ modulation of carbon nitride by single In atom, this study provides a ground-breaking insight for reactivity enhancement from a double-gain view of bulk structural control and surface atomic arrangement for CO₂-reduction photocatalysts.     

Synergistic Manipulation of Zn2+ Ion Flux and Nucleation Induction Effect Enabled by 3D Hollow SiO2/TiO2/Carbon Fiber for Long-Lifespan and Dendrite-Free Zn–Metal Composite Anodes

Aqueous rechargeable zinc–metal batteries are a promising candidate for next-generation energy storage devices due to their intrinsic high capacity, low cost, and high safety. However, uncontrollable dendrite formation is a serious problem, resulting in limited lifespan and poor coulombic efficiency of zinc–metal anodes. To address these issues, a 3D porous hollow fiber scaffold with well-dispersed TiO₂, SiO₂, and carbon is used as superzincophilic host materials for zinc anodes. The amorphous TiO₂ and SiO₂ allow for controllable nucleation and deposition of metal Zn inside the porous hollow fiber even at ultrahigh current densities. Furthermore, the as-fabricated interconnected conductive hollow SiO₂ and TiO₂ fiber (HSTF) possess high porosity, high conductivity, and fast ion transport. Meanwhile, the HSTF exhibits remarkable mechanical strength to sustain massive Zn loading during repeated cycles of plating/stripping. The HSTF with interconnected conductive network can build a uniform electric field, redistributing the Zn²⁺ ion flux and resulting in smooth and stable Zn deposition. As a result, in symmetrical cells, the Zn@HSTF electrode delivers a long cycle life of over 2000 cycles at 20 mA cm⁻² with low overpotential (≈160 mV). The excellent cycling lifespan and low polarization are also realized in Zn@HSTF//MnO₂ full cells.     

Regulation of Cathode Mass and Charge Transfer by Structural 3D Engineering for Protonic Ceramic Fuel Cell at 400 °C

Lowering the operating temperature (ideally below 400 °C) for solid oxide fuel cell (SOFC) technology deployment has been an important transition that introduces the benefit of reduced operational costs and system durability. However, the key technical issue limiting the transition is the sluggish cathodic performance, namely the oxygen reduction reaction (ORR) rate of the conventional sponge-like cathode dramatically drops as the temperature reduces. In this paper, 3D engineering of a cathode is conducted on a protonic ceramic fuel cell to obtain an enhanced ORR between 400 and 600 °C. Compared with a cell using a conventional sponge-like cathode, 3D engineering improves the cathode ORR by 41% at 400 °C with a peak power density of 0.410 W cm⁻². A phase field simulation is applied to assist the engineering by understanding the competition between the cathode mass and charge transfer with different cathode porosities. The results show that structural engineering of existing well-developed cathodes is a simple and effective method to promote cathode ORR for low temperature SOFC by regulating the mass and charge transfer.     

A “Nano-Courier” for Precise Delivery of Acetylcholine and Melatonin by C5a-Targeted Aptamers Effectively Attenuates Reperfusion Injury of Ischemic Stroke

Overactive inflammatory response and excessive oxidative stress are the main pathophysiological culprits for cerebral ischemia/reperfusion injury (IRI) that arouse neuronal damage . The neurotransmitter acetylcholine (ACh) exerts anti-inflammatory roles by stimulating α7 nicotinic acetylcholine receptor (α7nAChR) on microglia to activate the cholinergic anti-inflammatory pathway. Simultaneously, as a circadian rhythm-dependent hormone , melatonin (MT) possesses promising neuroprotective effects that eliminate reactive oxygen species (ROS) in the ischemic region. Relying on these, a biocompatible fluorescein isothiocyanate (FITC)-labeled SiO₂@PAA-MT/ACh nanospheres are constructed to effectively alleviate oxidative stress and polarize microglial phenotype to suppress inflammatory response in cerebral IRI. Despite of biosafety and curative effects of ACh and MT, the poor aggregation in ischemic penumbra hinders their neuroprotection. To address that, complement component 5a (C5a) is used as a molecular target for delivery of ACh and MT. C5a conspicuously exists at local inflammatory sites of cerebral IRI, recruits immune cells, and mediates further release of inflammatory cytokines. Upon binding of anti-C5a (aC5a) aptamers onto FITC-labeled SiO₂@PAA-MT/ACh nanospheres, they can effectively target the ischemic penumbra and promote neurological recovery. Taken together, the current study suggests that the FITC-labeled SiO₂@PAA-MT/ACh-aC5a nanospheres after intravenous (i.v.) administration can act as an effective targeted nanotherapy to salvage neurons in cerebral IRI.     

High-Density Atomic Fe–N4/C in Tubular,Biomass-Derived,Nitrogen-Rich Porous Carbon as Air-Electrodes for Flexible Zn–Air Batteries

Developing low-cost single-atom catalysts (SACs) with high-density active sites for oxygen reduction/evolution reactions (ORR/OER) are desirable to promote the performance and application of metal–air batteries. Herein, the Fe nanoparticles are precisely regulated to Fe single atoms supported on the waste biomass corn silk (CS) based porous carbon for ORR and OER. The distinct hierarchical porous structure and hollow tube morphology are critical for boosting ORR/OER performance through exposing more accessible active sites, providing facile electron conductivity, and facilitating the mass transfer of reactant. Moreover, the enhanced intrinsic activity is mainly ascribed to the high Fe single-atom (4.3 wt.%) loading content in the as-synthesized catalyst.Moreover, the ultra-high N doping (10 wt.%) can compensate the insufficient OER performance of conventional Fe N C catalysts. When as-prepared catalysts are assembled as air-electrodes in flexible Zn–air batteries, they perform a high peak power density of 101 mW cm⁻², a stable discharge–charge voltage gap of 0.73 V for >44 h, which shows a great potential for Zinc–air battery. This work provides an avenue to transform the renewable low-cost biomass materials into bifunctional electrocatalysts with high-density single-atom active sites and hierarchical porous structure.