Search

It remains a challenge for platinum-based oxygen reduction reaction catalysts to simultaneously possess high mass activity and high durability in proton-exchange-membrane fuel cells. Herein, we report ultrathin holey nanotube (UHT)-structured Pt-M (M = Ni, Co) alloy catalysts that achieve unprecedented comprehensive performance. The nanotubes have ultrathin walls of 2-3 nm and construct self-supporting network-like catalyst layers with thicknesses of less than 1 μm, which have efficient mass transfer and 100% surface exposure, thus enabling high utilization of Pt atoms. Combined with the high intrinsic activity produced by the alloying effect, the catalysts achieve high mass activity. Moreover, the nanotube structure not only avoids the agglomeration problem of nanoparticles, but the low curvature of the tube wall also gives UHT a low surface energy (less than 1/3 of that of the same size nanoparticle), so UHT is more resistant to the Ostwald ripening and is stable. For the first time, the U.S. DOE mass activity target and dual durability targets for load and start-stop cycles are achieved on one catalyst. This study provides an effective structural strategy for the preparation of electrocatalysts with high atomic efficiency and excellent durability.

Constructing the strong interaction between the matrix and the active centers dominates the design of high-performance electromagnetic wave (EMW) absorption materials. However, the interaction-relevant absorption mechanism is still unclear, and the design of ultrahigh reflection loss (

To develop efficient and durable acidic oxygen–reduction–reaction (ORR) catalysts based on all platinum group metals (PGMs) is crucial for large-scale application of proton-exchange membrane fuel cells (PEMFCs) but challenging. Here, we report a nitrogen coordination-induced strong metal–support interaction that can tune the surface atoms of ORR-inactive PGM clusters into efficient and durable active sites. Taking Rh as an example, the carbonization of Rh-overdoped zeolitic imidazolate framework-8 results in a large number of Rh clusters (with a little atomic Rh) in porous nitrogen-doped carbon. The cluster surface atoms coordinate with the nitrogen of the carbon support, forming much stronger metal–support interactions than that of common N-doped carbon-supported metal nanoparticles. The activity of surface-activated Rh clusters is close to that of Pt/C. The regulation rules for the surface active sites inherit most of the characteristics of the corresponding single-atom catalysts, but without their severe instability problem. This surface activation strategy has also shown applicable to other PGMs, thereby it is a promising way to alleviate the reliance of PEMFCs on platinum.

The intricate roles of the trimodal pores of Fe–N–C fuel cell catalysts are clarified through microwave-assisted water saturation detection. An optimal spatial porosity is thus identified to achieve a record-high power density.

A sandwich Ti3C2Tx/MoS2−xPx heterostructure with outstanding HER activity and excellent long-term durability was constructed by a hydrothermal and phosphorization approach. The sandwich heterostructure and P doping promote excellent HER performance.

Silica-based ceramics have been explored extensively as a class of versatile materials for various applications in architecture, catalysis, energy, machinery, and biomedical engineering. Nevertheless, comprehensive information on silica-based ceramic and electromagnetic microwave (EMW) absorption is scarce, although excellent progress has been made in this field. Here, recent progress in the investigation of silica-based ceramics toward EMW absorption is reviewed. We first introduced the basis of ceramics (characteristics, classification, synthetic methods, potential applications). Subsequently, the silica-based ceramics, including Si-based oxides and alloys, SiOC/SiC/Si3N4/SiCN-based composite, Ti3SiC2 and composite for EMW absorption were systematically summarized. Notably, the fabrication strategies, absorption properties, and mechanisms of silica-based ceramics are described in detail, with a focus on structure and component design. Lastly, the prospects and ongoing challenges of this field in the future are presented. This review is expected to learn from the past and achieve progress toward the future of silica-based ceramic for EMW absorption.

The lotus seedpod-based activated carbon (LSAC) is derived from pyrolysis of lotus seedpod as biomass carbon precursor, and Co3O4 is then deposited to LSAC by oxidation-precipitation and crystallization process of Co ions from Co(NO3)2 solution. The Co3O4 particles uniformly decorate on the surface and/or the inner channels of LSAC. The optimal reflection loss (RL) value of LSAC/Co3O4-paraffin wax (PW) composite reaches −39.8 dB, and the bandwidth for RL below −10 dB and −20 dB are 10.3 and 3.0 GHz, respectively, much better than that of LSAC-PW composite for the higher magnetic loss. The addition of Co3O4 particles in LSAC-PW composite significantly enhance the RL values in various thicknesses. The channels of the LSAC and decorated Co3O4 can improve the abilities of multiple scattering, dipole polarization, interface polarization and magnetic loss. This composite provides a promising method to construct high performance absorbers by using biomass carbon to tune the dielectric properties of the ferromagnetic materials.

Stretchable conductive fibers are an important component of wearable electronic textiles, but often suffer from a decrease in conductivity upon stretching. The use of liquid metal (LM) droplets as conductive fillers in elastic fibers is a promising solution. However, there is an urgent need to develop effective strategies to achieve high adhesion of LM droplets to substrates and establish efficient electron transport paths between droplets. Here, we use large-sized MXene two-dimensional conductive materials to modify magnetic LM droplets and prepare MXene/magnetic LM/poly(styrene-butadiene-styrene) composite fibers (MLMS fibers). The MXene sheets decorated on the surface of magnetic LM droplets not only enhance the droplet adhesion to substrate but also bridge adjacent droplets to establish efficient conductive paths. MLMS fibers show several-fold improvements in tensile strength and elongation and a 30-fold increase in conductivity compared with pure LM-filled fibers. These conductive fibers can be easily woven into multifunctional textiles, which exhibit strong electromagnetic interference shielding and stable Joule heating performances even under large tensile deformation. In addition, other advantages of MLMS textiles, such as high gas/liquid permeability, strong chemical resistance (acid and alkaline conditions), high/low-temperature tolerance (-40-150 °C) and water washability, make them particularly suitable for wearable applications.

Summary Smart electromagnetic interference (EMI) shielding materials with tunable EM wave response characteristics are attractive for future EM devices. Here, we report an off/on switchable EMI shielding material that can be tuned from EM wave transmission to shielding and vice versa by mechanical compression and decompression. This smart material is prepared by filling conductive carbon nanoparticles into wood-derived lamellar carbon aerogel, showing reversible compressibility and strain-sensitive conductivity. The original aerogel has good impedance matching and low dielectric loss, allowing the EM wave to pass through. Mechanical compression enables the carbon nanoparticles to establish highly conductive pathways in the aerogel, which significantly increases the conductivity of aerogel and thus activates its EMI shielding performance. This function switch is reversible by repeatedly compressing and decompressing the aerogel. The availability of such a never-before-realized off/on switchable EMI shielding material provides an opportunity for the development of advanced smart EM devices.

Hydrogen storage materials are the key to hydrogen energy utilization. However, current materials can hardly meet the storage capacity and/or operability requirements of practical applications. Here we report an advancement in hydrogen storage performance and related mechanism based on a hydrofluoric acid incompletely etched MXene, namely, a multilayered Ti2CTx (T is a functional group) stack that shows an unprecedented hydrogen uptake of 8.8 wt% at room temperature and 60 bar H2. Even under completely ambient conditions (25 °C, 1 bar air), Ti2CTx is still able to retain ~4 wt% hydrogen. The hydrogen storage is stable and reversible in the material, and the hydrogen release is controllable by pressure and temperature below 95 °C. The storage mechanism is deduced to be a nanopump-effect-assisted weak chemisorption in the sub-nanoscale interlayer space of the material. Such a storage approach provides a promising strategy for designing practical hydrogen storage materials. An incompletely etched Ti2CTx stack exhibits highly reversible hydrogen storage under near-ambient conditions by nanopump-effect-assisted weak chemisorption.

Environment-friendly Fe-based material@N-doped carbon nanoparticles imbedded in polylactic acid (PLA) matrix are prepared and applied in microwave absorption field. In the synthesis process, polydopamine (PDA) in the precursor could rationally regulate the phases of the iron-based particles and carbon contents. It turns out that optimizing the chemical composition plays a vital role in modulating microwave absorption performance. For instance, the maximum reflection loss (RLmax) for Fe@N-doped carbon particles (S-120) reaches −61.6 dB (12.56 GHz, 2.1 mm), and the effective bandwidth is 4.48 GHz (from 13.52 GHz to 18 GHz) with a thickness of only 1.7 mm. The excellent microwave absorption performance could be attributed to perfect impedance matching brought by the synergies of multiple components. Moreover, the microwave absorbers display not only high microwave absorption performance but also environment-friendly characteristics that can avoid leaving stubborn waste after failure. The preparation process of the composite is pollution-free and the PLA in the composite can almost be naturally degraded within one month under simulated marine environment. This work may provide a new perspective on preparing high-efficient functional materials which are also harmless to the environment.

Great effort has recently been made to develop unique nanomaterials with superior reflection loss (RL), thin thickness, wide bandwidth and low density to improve their efficiency in electromagnetic (EM) microwave absorption, while maintaining a simple manufacturing process. The use of traditional nanomaterials with magnetic loss or dielectric loss, of course, not only makes the last requirement hard to meet but also restricts the thickness of absorber, and limits mass production. Recently, some promising nanomaterials with excellent conduction loss and polarization loss have been explored which promise to enable unique nanostructures with multiple reflections and interfacial polarization. Herein, we discuss the EM microwave absorption theory. Then, we review recent achievements in manufacturing EM microwave absorption materials, particularly focusing on the unique and key factors in design and control of structures and components. In addition, current challenges are presented, and prospects for future development in this rapidly blossoming field are discussed.

To make use of two waste natural corncob and rosewood, activated carbons are obtained through KOH activation at 1073 K. The two samples show sheet like morphology with some swells on the surface of the corncob activated carbon and pores in the rosewood activated carbon. The higher ID/IG value of rosewood activated carbon for the Raman spectrum measurement indicates its lower graphitization degree than corncob activated carbon, which is proved by X-ray diffraction patterns. The higher real and imaginary parts of the complex permittivity for the rosewood activated carbon are benefited from the differences of morphology and graphitization degree of the two samples. Apart from the dipole polarization, the charge polarization and interfacial polarization also contribute to the dielectric loss for the porous rosewood activated carbon.

Catalysts play a critical role in improving the hydrogen storage kinetics in Mg/MgH2 system. Exploring highly efficient catalysts and catalyst design principles are hot topics but challenging. The catalytic activity of metallic elements on dehydrogenation kinetics generally follows a sequence of Ti>Nb>Ni>V>Co>Mo. Herein, we report a highly efficient alloy catalyst composed of low-active elements of Mo and Ni (i.e. MoNi alloy) for MgH2 particles. MoNi alloy nanoparticles show excellent catalytic effect, even outperforming most advanced Ti-based catalysts. The synergy between Mo and Ni elements can promote the break of Mg-H bonds and the dissociation of hydrogen molecules, thus significantly improves the kinetics of Mg/MgH2 system. The MoNi-catalyzed Mg/MgH2 system can absorb and release 6.7 wt.% hydrogen within 60 s and 10 min at 300 °C, respectively, and exhibits excellent cycling stability and low-temperature hydrogen storage performance. This study provides a strategy for designing efficient catalysts for hydrogen storage materials using the synergy of metal elements.

Design and synthesis of highly efficient and cost-effective bifunctional catalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) remain a big challenge. Herein, a quaternary amorphous nanocompound Ni-Fe-P-B has been synthesized by a facile, scalable co-reduction method. The Ni-Fe-P-B exhibits high electrocatalytic activity and outstanding durability for both HER and OER, delivering a current density of 10 mAcm−2 at overpotentials of 220 and 269 mV, respectively. When loaded on carbon fiber paper (CFP) as a bifunctional catalyst, the Ni-Fe-P-B@CFP electrode requires a low cell voltage of 1.58 V to obtain 10 mAcm−2 for overall water splitting with negligible recession over 60 h. The excellent catalytic performances of Ni-Fe-P-B mainly benefit from the metal-metalloid combined composition modulation and the unique amorphous structure. This work provides new insights into the design of robust bifunctional catalysts for water splitting, and may promote the development of multicomponent amorphous catalysts.

Carbon nanomaterials have abundant sources but are difficult to use directly as a support for single atom catalysts (SACs) due to the lack of strong anchoring forces to restrict the movement and aggregation of metal atoms during the high-temperature heat treatment. Herein, we report a “self-catalysis” method for the synthesis of ferrous metal single-atom catalysts (SACs) FM–N–C (FM = Fe, Co, and Ni) with ∼2 wt% metal loadings on a carbon black support. The combination of experimental and theoretical evidence reveals a self-catalytic process from FM atoms to FM–N4 species, which involves (1) the adsorption of FM ions on the surface-oxidized carbon nanoparticles via oxygen coordination bonds (FM–O); (2) the catalytic decomposition of ammonia to nitrogen radicals on the FM atoms; (3) the replacement of coordinating oxygen with nitrogen. The precoordination of FM with oxygen is the key to the synthesis and reduces the energy barrier of ammonia decomposition and nitrogen bonding to the FM atoms. Thus, the formation of the FM–N4 species at a mild temperature of 600 °C is enabled. The as-synthesized FM–N–C SACs exhibit high catalytic activities towards O2 and/or CO2 reduction reactions. In contrast to the metal–organic framework-based SACs in which the MOF support significantly changes in size and weight, the self-catalysis technique is “minimally invasive” to the carbon support, thus benefiting the structural design of SACs by taking advantage of the abundant morphologies of the carbon nanomaterials.

To find an OER catalyst with satisfactory catalytic performance and affordable cost is of great importance to the development of many new energy devices. In this work, we present a simple and effective strategy to synthesize a series of amorphous MoCo lamellar hydroxide through one-step chemical co-precipitation. Systematic investigations show that different functional agents (2-MIM, NaOH, NH4OH) in fabrication process result in different micromorphology of catalyst, thus influencing the electrocatalytic performance of catalyst. Also, adding amount of Mo could influence the intrinsic catalytic property of catalyst. Samples synthesized with appropriate functional agent addition and optimized Mo addition exhibit amorphous nature and bended nanosheet morphology, as well as highest intrinsic catalytic activity, showing a low overpotential of 290 mV at 10 mA cm-2 and a small Tafel slope of 55 mV dec-1 in 1M KOH solution. Additionally, the catalytic performance of the sample shows just small decay after 50 h chronopotentiometry test and 3000 CV cycles, exhibiting the ultra-stable catalytic activity of the catalyst. This work provides a possible large-scale commercial production strategy of OER catalysts with promising performance and low fabrication cost.

Natural alginate fibers are used as templates to fabricate CoFe alloy-decorated hierarchically porous carbon fibers (HPCFs). Due to the coordination with negatively charged α−L−guluronate blocks, transition metal (TM) ions could be confined in the “egg box” structure of alginate, which convert to CoFe alloy particles that homogenously embedded in HPCFs during carbonization. The composition and weight ratio of magnetic particles could be well controlled by adjusting the absorbed TM ions and carbonization temperature. Unlike previous analogues with uniform mesopores, this composite fiber simultaneously possesses a number of mesopores and a high proportion of submicron macropores which not only facilitates the accommodation of large-sized CoFe particles, but also induces abundant interfacial polarization and EMW multi-scattering. Remarkably, the CoFe/HPCF with a filler loading as low as 15 wt% in matrix achieves an extremely strong reflection loss of −69.1 dB at a thin thickness of 1.6 mm, and its effective absorption bandwidth reaches 5.2 GHz, showing better comprehensive properties than other similar absorbers. This work highlights the importance of hierarchically porous structure (especially macroporous structure) on improving EMW absorption. The synthetic strategy is green, low cost, scalable, and can be used to synthesize other highly efficient composite absorbers.

Unsatisfactory reflection loss (RL) and thick thickness of the absorber severely limit the practical application of advanced electromagnetic (EM) microwave absorbers. Herein, we report a heterogene...