Comparison of copper and graphene-assembled films in 5G wireless communication and THz electromagnetic-interference shielding.

Since first developed, the conducting materials in wireless communication and electromagnetic interference (EMI) shielding devices have been primarily made of metal-based structures. Here, we present a graphene-assembled film (GAF) that can be used to replace copper in such practical electronics. The GAF-based antennas present strong anticorrosive behavior. The GAF ultra-wideband antenna covers the frequency range of 3.7 GHz to 67 GHz with the bandwidth (BW) of 63.3 GHz, which exceed ~110% than the copper foil-based antenna. The GAF Fifth Generation (5G) antenna array features a wider BW and lower sidelobe level compared with that of copper antennas. EMI shielding effectiveness (SE) of GAF also outperforms copper, reaching up to 127 dB in the frequency range of 2.6 GHz to 0.32 THz, with a SE per unit thickness of 6,966 dB/mm. We also confirm that GAF metamaterials exhibit promising frequency selection characteristics and angular stability as flexible frequency selective surfaces.

Precise arrangement of metal atoms at the interface by a thermal printing strategy.

The kinetics and pathway of most catalyzed reactions depend on the existence of interface, which makes the precise construction of highly active single-atom sites at the reaction interface a desirable goal. Herein, we propose a thermal printing strategy that not only arranges metal atoms at the silica and carbon layer interface but also stabilizes them by strong coordination. Just like the typesetting of Chinese characters on paper, this method relies on the controlled migration of movable nanoparticles between two contact substrates and the simultaneous emission of atoms from the nanoparticle surface at high temperatures. Observed by in situ transmission electron microscopy, a single Fe3O4 nanoparticle migrates from the core of a SiO2 sphere to the surface like a droplet at high temperatures, moves along the interface of SiO2 and the coated carbon layer, and releases metal atoms until it disappears completely. These detached atoms are then in situ trapped by nitrogen and sulfur defects in the carbon layer to generate Fe single-atom sites, exhibiting excellent activity for oxygen reduction reaction. Also, sites' densities can be regulated by controlling the size of Fe3O4 nanoparticle between the two surfaces. More importantly, this strategy is applicable to synthesize Mn, Co, Pt, Pd, Au single-atom sites, which provide a general route to arrange single-atom sites at the interface of different supports for various applications.

Identification of Fenton-like active Cu sites by heteroatom modulation of electronic density.

Developing heterogeneous catalysts with atomically dispersed active sites is vital to boost peroxymonosulfate (PMS) activation for Fenton-like activity, but how to controllably adjust the electronic configuration of metal centers to further improve the activation kinetics still remains a great challenge. Herein, we report a systematic investigation into heteroatom-doped engineering for tuning the electronic structure of Cu-N4 sites by integrating electron-deficient boron (B) or electron-rich phosphorus (P) heteroatoms into carbon substrate for PMS activation. The electron-depleted Cu-N4/C-B is found to exhibit the most active oxidation capacity among the prepared Cu-N4 single-atom catalysts, which is at the top rankings of the Cu-based catalysts and is superior to most of the state-of-the-art heterogeneous Fenton-like catalysts. Conversely, the electron-enriched Cu-N4/C-P induces a decrease in PMS activation. Both experimental results and theoretical simulations unravel that the long-range interaction with B atoms decreases the electronic density of Cu active sites and down-shifts the d-band center, and thereby optimizes the adsorption energy for PMS activation. This study provides an approach to finely control the electronic structure of Cu-N4 sites at the atomic level and is expected to guide the design of smart Fenton-like catalysts.

Alleviating OH Blockage on the Catalyst Surface by the Puncture Effect of Single-Atom Sites to Boost Alkaline Water Electrolysis.

Nonprecious transition metal catalysts have emerged as the preferred choice for industrial alkaline water electrolysis due to their cost-effectiveness. However, their overstrong binding energy to adsorbed OH often results in the blockage of active sites, particularly in the cathodic hydrogen evolution reaction. Herein, we found that single-atom sites exhibit a puncture effect to effectively alleviate OH blockades, thereby significantly enhancing the alkaline hydrogen evolution reaction (HER) performance. Typically, after anchoring single Ru atoms onto tungsten carbides, the overpotential at 10 mA·cm-2 is reduced by more than 130 mV (159 vs 21 mV). Also, the mass activity is increased 16-fold over commercial Pt/C (MA100 = 17.3 A·mgRu-1 vs 1.1 A·mgPt-1, Pt/C). More importantly, such electrocatalyst-based alkaline anion-exchange membrane water electrolyzers can exhibit an ultralow potential (1.79 Vcell) and high stability at an industrial current density of 1.0 A·cm-2. Density functional theory (DFT) calculations reveal that the isolated Ru sites could weaken the surrounding local OH binding energy, thus puncturing OH blockage and constructing bifunctional interfaces between Ru atoms and the support to accelerate water dissociation. Our findings exhibit generality to other transition metal catalysts (such as Mo) and contribute to the advancement of industrial-scale alkaline water electrolysis.

A Bioinspired Single-Atom Fe Nanozyme with Excellent Laccase-Like Activity for Efficient Aflatoxin B1 Removal.

The applications of natural laccases are greatly restricted because of their drawbacks like poor biostability, high costs, and low recovery efficiency. M/NC single atom nanozymes (M/NC SAzymes) are presenting as great substitutes due to their superior enzyme-like activity, excellent selectivity and high stability. In this work, inspired by the catalytic active center of natural enzyme, a biomimetic Fe/NC SAzyme (Fe-SAzyme) with O2-Fe-N4 coordination is successfully developed, exhibiting excellent laccase-like activity. Compared with their natural counterpart, Fe-SAzyme has shown superior catalytic efficiency and excellent stability under a wide range of pH (3.0-9.0), temperature (4-80 °C) and NaCl strength (0-300 mm). Interestingly, density functional theory (DFT) calculations reveal that the high catalytic performance is attributed to the activation of O2 by O2-Fe-N4 sites, which weakened the O─O bonds in the oxygen-to-water oxidation pathway. Furthermore, Fe-SAzyme is successfully applied for efficient aflatoxin B1 removal based on its robust laccase-like catalytic activity. This work provides a strategy for the rational design of laccase-like SAzymes, and the proposed catalytic mechanism will help to understand the coordination environment effect of SAzymes on laccase-like catalytic processes.

Precise Modulation of the Coordination Environment of Single Cu Site Catalysts to Regulate the Peroxymonosulfate Activation Pathway for Water Remediation.

Single atom site catalysts (SACs) with atomically dispersed active sites can be expected to be potential ideal catalysts for accurately modulating the persulfate activation pathway during the water remediation process because of their well-defined structure and the maximum metallic atom utilization. In this paper, a series of Cu SACs with different coordination environments were synthesized to elaborately regulate the peroxymonosulfate activation pathway in AOPs to clarify active species generation and transformation in water remediation. The degradation rate constants (kobs) of Cu-N2, Cu-N3, and Cu-N4 were 0.028, 0.021, and 0.015 min-1, respectively. Cu-N2 SACs exhibited a noticeable enhanced performance for bisphenol A (BPA) removal from water compared to that of the Cu-Nx SACs (x = 3, 4), accompanied by peroxymonosulfate (PMS) activation pathway variation. As shown by experimental and theoretical results, the PMS activation pathway was transformed from ROS to electron transfer with nitrogen coordination numbers decreasing from 4 to 2, which can be ascribed to the uneven charge distribution of Cu sites as well as upshifts in the d-band center, and thereby optimized electron transfer for PMS activation. Furthermore, the increasing nitrogen vacancies of single Cu site catalysts can also result in more unoccupied 3d orbitals of Cu atoms in SACs, thereby improving the intermediates' (PMS and BPA) adsorption-desorption process and BPA removal performance. These findings provided a beneficial approach for the coordination number regulation of SACs in water remediation.

Self-Optimized Ligand Effect of Single-Atom Modifier in Ternary Pt-Based Alloy for Efficient Hydrogen Oxidation.

Modifying the atomic and electronic structure of platinum-based alloy to enhance its activity and anti-CO poisoning ability is a vital issue in hydrogen oxidation reaction (HOR). However, the role of foreign modifier metal and the underlying ligand effect is not fully understood. Here, we propose that the ligand effect of single-atom Cu can dynamically modulate the d-band center of Pt-based alloy for boosting HOR performance. By in situ X-ray absorption spectroscopy, our research has identified that the potential-driven structural rearrangement into high-coordination Cu-Pt/Pd intensifies the ligand effect in Pt-Cu-Pd, leading to enhanced HOR performance. Thereby, modulating the d-band structure leads to near-optimal hydrogen/hydroxyl binding energies and reduced CO adsorption energies for promoting the HOR kinetics and the CO-tolerant capability. Accordingly, PtPdCu1/C exhibits excellent CO tolerance even at 1,000 ppm impurity.

Stabilizing Few-Atom Platinum Clusters by Zinc Single-Atom-Glue for Efficient Anti-Markovnikov Alkene Hydrosilylation.

Few-atom metal clusters (FAMCs) exhibit superior performance in catalyzing complex molecular transformations due to their special spatial environments and electronic states, compared to single-atom catalysts (SACs). However, achieving the efficient and accurate synthesis of FAMCs while avoiding the formation of other species, such as nanoparticles and SACs, still remains challenges. Herein, we report a two-step strategy for synthesis of few-atom platinum (Pt) clusters by predeposition of zinc single-atom-glue (Zn1) on MgO nanosheets (Ptn-Zn1/MgO), where FAMCs can be obtained over a wide range of Pt contents (0.09 to 1.45 wt %). Zn atoms can act as Lewis acidic sites to allow electron transfer between Zn and Pt through bridging O atoms, which play a crucial role in the formation and stabilization of few-atom Pt clusters. Ptn-Zn1/MgO exhibited a high selectivity of 93 % for anti-Markovnikov alkene hydrosilylation. Moreover, an excellent activity with a turnover frequency of up to 1.6×104 h-1 can be achieved, exceeding most of the reported Pt SACs. Further theoretical studies revealed that the Pt atoms in Ptn-Zn1/MgO possess moderate steric hindrance, which enables high selectivity and activity for hydrosilylation. This work presents some guidelines for utilizing atomic-scale species to increase the synthesis efficiency and precision of FAMCs.

Axial Dual Atomic Sites Confined by Layer Stacking for Electroreduction of CO2 to Tunable Syngas.

Arranging atoms in an orderly manner at the atomic scale to create stable polyatomic structures is a very challenging task. In this study, we have developed three-dimensional confinement areas on the two-dimensional surface by creating regional defects. These areas are composed of vertically stacked graphene layers, where Ni and Fe atoms are anchored concentrically to form axial dual atomic sites in high yield. These sites can be used to produce tunable syngas through the electroreduction of CO2. Theoretical calculations indicate that the Ni sites vertically regulate the charge distribution of the adjacent Fe sites in the layer below, resulting in a lower d-band center. This, in turn, weakens the adsorption of the *CO intermediate and inhibits the production of H2 at the Fe site. Our research presents a novel approach for concentrated creation of dual atomic sites by building a confinement-selective surface.

Coupling Single-Atom Sites and Ordered Intermetallic PtM Nanoparticles for Efficient Catalysis in Fuel Cells.

The design of an efficient catalytic system with low Pt loading and excellent stability for the acidic oxygen reduction reaction is still a challenge for the extensive application of proton-exchange membrane fuel cells. Here, a gas-phase ordered alloying strategy is proposed to construct an effective synergistic catalytic system that blends PtM intermetallic compounds (PtM IMC, M = Fe, Cu, and Ni) and dense isolated transition metal sites (M-N4 ) on nitrogen-doped carbon (NC). This strategy enables Pt nanoparticles and defects on the NC support to timely trap flowing metal salt without partial aggregation, which is attributed to the good diffusivity of gaseous transition metal salts with low boiling points. In particular, the resulting Pt1 Fe1 IMC cooperating with Fe-N4 sites achieves cooperative oxygen reduction with a half-wave potential up to 0.94 V and leads to a high mass activity of 0.51 A  mgPt -1 and only 23.5% decay after 30 k cycles, both of which exceed DOE 2025 targets. This strategy provides a method for reducing Pt loading in fuel cells by integrating Pt-based intermetallics and single transition metal sites to produce an efficient synergistic catalytic system.

Synergistic Roles of the CoO/Co Heterostructure and Pt Single Atoms for High-Efficiency Electrocatalytic Hydrogenation of Lignin-Derived Bio-Oils.

Electrochemical hydrogeneration (ECH) of biomass-derived platform molecules, which avoids the disadvantages in utilizing fossil fuel and gaseous hydrogen, is a promising route toward value-added chemicals production. Herein, we reported a CoO/Co heterostructure-supported Pt single atoms electrocatalyst (Pt1-CoO/Co) that exhibited an outstanding performance with a high conversion (>99%), a high Faradaic efficiency (87.6%), and robust stability (24 recyclability) at -20 mA/cm2 for electrochemical phenol hydrogenation to high-valued KA oil (a mixture of cyclohexanol and cyclohexanone). Experimental results and the density functional theory calculations demonstrated that Pt1-CoO/Co presented strong adsorption of phenol and hydrogen on the catalyst surface simultaneously, which was conducive to the transfer of the adsorbed hydrogen generated on the single atom Pt sites to activated phenol, and then, ECH of phenol with high performance was achieved instead of the direct hydrogen evolution reaction. This work described that the multicomponent synergistic single atom catalysts could effectively accelerate the ECH of phenol, which could help the achievement of large-scale biomass upgrading.

A Double Atomic-Tuned RuBi SAA/Bi@OG Nanostructure with Optimum Charge Redistribution for Efficient Hydrogen Evolution.

Charge redistribution on surface of Ru nanoparticle can significantly affect electrocatalytic HER activity. Herein, a double atomic-tuned RuBi SAA/Bi@OG nanostructure that features RuBi single-atom alloy nanoparticle supported by Bi-O single-site-doped graphene was successfully developed by one-step pyrolysis method. The alloyed Bi single atom and adjacent Bi-O single site in RuBi SAA/Bi@OG can synergistically manipulate electron transfer on Ru surface leading to optimum charge redistribution. Thus, the resulting RuBi SAA/Bi@OG exhibits superior alkaline HER activity. Its mass activity is up to 65000 mA mg-1 at an overpotential of 150 mV, which is 72.2 times as much as that of commercial Pt/C. DFT calculations reveal that the RuBi SAA/Bi@OG possesses the optimum charge redistribution, which is most beneficial to strengthen adsorption of water and weaken hydrogen-adsorption free energy in HER process. This double atomic-tuned strategy on surface charge redistribution of Ru nanoparticle opens a new way to develop highly efficient electrocatalysts.

Periodic One-Dimensional Single-Atom Arrays.

The orderly assembly of single atoms into highly periodic aggregates at the nanoscale is an intriguing but challenging process of high-precision atomic manufacturing. Here, we discover that an in-plane film surface shrinkage can induce molecular self-assembly to arrange single atoms with unconventional distribution, contributing them to periodic one-dimensional segregation on carbon stripes (one-dimensional single-atom arrays (SAA)). This originates from the fact that metal phthalocyanine (MPc) molecules gradually aggregate and melt to form a film under a thermal drive and the help of sodium chloride templates, accompanied by surface shrinkage, self-assembly, and deep carbonization. At the nanoscale, these periodic parallel arrays are formed due to MPc molecular interactions by π-π stacking. At the atomic scale, the single atoms are stabilized by the vertical phthalocyanine-derived multilayer graphene. This can significantly modify the electronic structure of the single-atom sites on the outermost graphene (e.g., Fe-based SAA), thus optimizing the adsorption energy of oxygen intermediates and resulting in a superior oxygen reduction reaction (ORR) performance concerning disordered single atoms. Our findings provide a general route for orderly single-atom manufacturing (e.g., Fe, Co, and Cu) and an understanding of the relationship between orderly allocation and catalytic performance.

Precise Regulation of Iron Spin States in Single FeN4 Sites for Efficient Peroxidase-Mimicking Catalysis.

The catalytic activity and selectivity of single-atom sites catalysts is strongly dependent on the supports structure and central metal coordination environment. However, the further optimization of electronic configuration to improve the catalytic performance is usually hampered by the strong coordination effect between the support and metal atoms. Herein, it is discovered that enzyme-mimicking catalytic performance can be enhanced at the fixed coordination single-atom Fe sites by regulating the Fe spin states. The X-ray absorption fine structure, 57 Fe Mössbauer spectrum, and temperature-dependent magnetization measurements reveal that the spin states of Fe in single FeN4  sites can be well manipulated via changing the pyrolysis temperature. The intermediate-spin Fe sites catalyst (t2g 4 eg 1) demonstrates a much higher peroxidase-mimicking activity in comparison with high-spin structure (t2g 3 eg 2). More importantly, the based enzymes system realizes sensitive detection of H2 O2  and glucose by colorimetric sensors with high catalytic activity and selectivity. Furthermore, theoretical calculations unveil that the intermediate-spin FeN4  promotes the OH* desorption process, thus greatly reducing the reaction energy barrier. These findings provide a route to design highly active enzyme-mimicking catalysts and an engineering approach for regulating spin states of metal sites to enhance their catalytic performance.

Effects of body positions and garment design on the performance of a personal air cooling/heating system.

Heating and cooling efficiencies of a personal air thermoregulatory system are not only determined by the physics of energy conversion efficiency but also influenced by the interactions between human body and clothing microenvironment. It was found that for a wearable air ventilating system, sedentary position can lead to higher heating and cooling power than standing position. Also, leaning on the chair backrest during sitting can further improve the air cooling performance in hot condition compared with a non-leaning position. These improvements are mainly attributed to the change of clothing microclimate at chest and back areas, where cooling/heating air is directed. It was also found locations of air outlets in a wearable air ventilating system can affect the cooling/heating performance. With the improved understanding of the influence of human and design factors, the study provides a guideline for the design of personal air thermoregulatory systems used for different body positions.

Design of Co-Cu Diatomic Site Catalysts for High-efficiency Synergistic CO2 Electroreduction at Industrial-level Current Density.

Single atom catalysts (SACs) have been widely studied in the field of CO2 electroreduction, but industrial-level current density and near-unity product selectivity are still difficult to achieve. Herein, a diatomic site catalysts (DASCs) consisting of Co-Cu hetero-diatomic pairs is synthesized. The CoCu DASC exhibits excellent selectivity with the maximum CO Faradaic efficiency of 99.1 %. The CO selectivity can maintain above 95 % over a wide current density range from 100 mA cm-2 to 500 mA cm-2 . The maximum CO partial current density can reach to 483 mA cm-2 in flow cell, far exceed industrial-level current density requirements (>200 mA cm-2 ). Theoretical calculation reveals that the synergistic catalysis of the Co-Cu bimetallic sites reduce the activation energy and promote the formation of intermediate *COOH. This work shows that the introduction of another metal atom into SACs can significantly affect the electronic structure and then enhance the catalytic activity of SACs.

Rapid Controllable Synthesis of Atomically Dispersed Co on Carbon under High Voltage within One Minute.

Developing a rapid and low cost approach to access atomically dispersed metal catalysts (ADMCs) supported by carbon is important but still challenging. Here, an electric flash strategy using high voltage for the rapid fabrication of carbon-supported ADMCs within 1 min is reported. Continuous plasma arc results in nitrogen-doped carbon ultrathin nanosheets, while an intermittent spark pulse constructs carbon hollow nanospheres via blasting effect, and both structures are decorated with atomically dispersed cobalt. The latter catalyst shows a half-wave potential of 0.887 V versus RHE (47 mV higher than commercial Pt/C) in an oxygen reduction reaction (ORR) in alkaline media. The authors' work paves the way to rapid synthesis of carbon-supported ADMCs at both low cost and mass production.

Tailoring Unsymmetrical-Coordinated Atomic Site in Oxide-Supported Pt Catalysts for Enhanced Surface Activity and Stability.

The catalytic properties of supported metal heterostructures critically depend on the design of metal sites. Although it is well-known that the supports can influence the catalytic activities of metals, precisely regulating the metal-support interactions to achieve highly active and durable catalysts still remain challenging. Here, the authors develop a support effect in the oxide-supported metal monomers (involving Pt, Cu, and Ni) catalysts by means of engineering nitrogen-assisted nanopocket sites. It is found that the nitrogen-permeating process can induce the reconstitution of vacancy interface, resulting in an unsymmetrical atomic arrangement around the vacancy center. The resultant vacancy framework is more beneficial to stabilize Pt monomers and prevent diffusion, which can be further verified by the density functional theory calculations. The final Pt-N/SnO2 catalysts exhibit superior activity and stability for HCHO response (26.5 to 15 ppm). This higher activity allows the reaction to proceed at a lower operating temperature (100 °C). Incorporated with wireless intelligent-sensing system, the Pt-N/SnO2 catalysts can further achieve continuous monitoring of HCHO levels and cloud-based terminal data storage.

Coplanar Pt/C Nanomeshes with Ultrastable Oxygen Reduction Performance in Fuel Cells.

Developing highly stable and efficient catalysts toward the oxygen reduction reaction is important for the long-term operation in proton exchange membrane fuel cells. Reported herein is a facile synthesis of two-dimensional coplanar Pt-carbon nanomeshes (NMs) that are composed of highly distorted Pt networks (neck width of 2.05±0.72 nm) and carbon. X-ray absorption fine structure spectroscopy demonstrated the metallic state of Pt in the coplanar Pt/C NMs. Fuel cell tests verified the excellent activity of the coplanar Pt/C NM catalyst with the peak power density of 1.21 W cm-2 and current density of 0.360 A cm-2 at 0.80 V in the H2 /O2 cell. Moreover, the coplanar Pt/C NM electrocatalysts showed superior stability against aggregation, with NM structures preserved intact for a long-term operation of over 30 000 cycles for electrode measurement, and the working voltage loss was negligible after 120 h in the H2 /O2 single cell operation. Density-functional theory analysis indicates the increased vacancy formation energy of Pt atoms for coplanar Pt/C NMs, restraining the tendency of Pt dissolution and aggregation.

Stimuli-Responsive Manganese Single-Atom Nanozyme for Tumor Therapy via Integrated Cascade Reactions.

The single-atom enzyme (SAE) is a novel type of nanozyme that exhibits extraordinary catalytic activity. Here, we constructed a PEGylated manganese-based SAE (Mn/PSAE) by coordination of single-atom manganese to nitrogen atoms in hollow zeolitic imidazolate frameworks. Mn/PSAE catalyzes the conversion of cellular H2 O2 to . OH through a Fenton-like reaction; it also promotes the decomposition of H2 O2 to O2 and continuously catalyzes the conversion of O2 to cytotoxic . O2- via oxidase-like activity. The catalytic activity of Mn/PSAE is more pronounced in the weak acidic tumor environment; therefore, these cascade reactions enable the sufficient generation of reactive oxygen species (ROS) and effectively kill tumor cells. The prominent photothermal conversion property of the amorphous carbon can be utilized for photothermal therapy. Hence, Mn/PSAE exhibits significant therapeutic efficacy through tumor microenvironment stimulated generation of multiple ROS and photothermal activity.