Double transition metal nitrides and carbides (MXene) have garnered significant attention in the field of electromagnetic wave (EMW) absorption due to their distinctive structural properties. The design of efficient MXene-based EMW absorbers remains a formidable challenge in light of the high conductivity and strong van der Waals forces. In this work, we report for the first time the approach of the double-doping non-metal N and rare earth metal Ce-4f into Mo-MXene to construct Mo-MXene/MoO₂-N/Ce system. This process enables partial in-situ oxidation of Mo-MXene, thereby forming a heterostructure and enhancing the interface polarization. The introduction of Ce facilitates the hybridization between the 4f orbitals of rare earth Ce and the 4d orbitals of Mo, altering the electronic structure of Ce and Mo-MXene and promoting electron migration, which contributes to polarization loss. Furthermore, incorporating melamine into the precursor can induce N doping in Mo-MXene, thereby promoting dipolar polarization. Consequently, the double-doping of N and Ce enables the synergistic effects of interface polarization, dipole polarization, and conduction loss, leading to efficient EMW absorption. Therefore, at a frequency of 13.43 GHz and a matching thickness of 4.685 mm, the optimal reflection loss (R_L) value of Mo-MXene/MoO₂-N/Ce reaches −57.46 dB, which exceeds a large number of reported MXene-based absorbers. This research confirms that Mo-MXene/MoO₂-N/Ce is a promising EMW absorption material and provides valuable insights into modulating MXene-based EMW absorbers using rare earth elements.

Supercapacitors exhibit high power density and long-term cycle life time in energy-power applications. Multi-component metal oxides are promising electrode materials for supercapacitors, due to their multivalent cations and diverse charge/discharge kinetics. However, it is difficult to control the morphology of multi-component metal oxides and the regulation methodsareusually too complicated. In this work, CoMoO_x nanostructures were grown on the surface of nickel foam by using a simple one-step hydrothermal method. The controllable synthesis of Co₀Mo₁O_x ultra-thin nanosheets, Co₁Mo₂O_x interwoven nanosheets, Co₁Mo₁O_x nanoflowers and Co₂Mo₁O_x nanopillar structures was realized by adjusting the Co:Mo molar ratio. Among them, the unique structure of Co₁Mo₁O_x nanoflowers enabled high specific capacitance and excellent cycling stability, with a specific capacitance of as high as 1628.8 F·g^-1 at a current density of 5 A·g^-1, which is superior to numerous advanced Co/Mo-based electrode materials. The Co₁Mo₁O_x nanoflowers can still retain 93.5% of the specific capacitance after 2000 cycles of galvanostatic charge-discharge (GCD) cycling. In addition, asymmetric supercapacitors (ASCs) devices assembled with Co₁Mo₁O_x nanoflowers and activated carbon (AC) exhibited high energy density, delivering an energy density of 79.3 Wh·kg^-1 at a power density of 4 kW·kg^-1. This work provides a controllable synthesis strategy of multi-component metal oxide nanostructures and enriches self-supporting, binder-free, and high energy storage properties of electrode materials for pseudocapacitors.

Metal–organic frameworks (MOFs) have recently been under intense study for photocatalytic hydrogen evolution reaction (HER) as a class of crystalline porous materials. However, the efficiency of HER is still low due to the low separation efficiency of photo-generated carries of MOFs. Here, we report surface enriched Zr-MOFs (UiO-66, UiO-66-NH₂, UiO-66-SO₃H, UiO-66-NH₂-SO₃H) nanoparticles to be incorporated in polyacrylonitrile nanofibers, which were synthesized by suing electrospinning technology. By incorporating photocatalytic Zr-MOFs in flexible piezoelectric PAN nanofiber, the composite membranes exhibited both piezoelectric and photocatalytic effects. The piezoelectric fields of PAN generated due to the mechanical deformation promoted the separation of the photogenerated electrons and holes. The PAN/Zr-MOFs composite membranes showed higher hydrogen evolution activity under the synergistic effect of mechanical vibration and light irradiation than that under light irradiation alone. Among the PAN/Zr-MOFs composite membranes, the PAN/UiO-66-NH₂-SO₃ H nanofiber membranes showed the highest hydrogen evolution rate, reaching 2306 μmol^-1·g^-1·h^-1, which was 4.2 times higher than that of photocatalysis alone. The working mechanism for the promoted HER by the mechanical vibrations was attributed to the piezoelectric effect of the PAN nanofibers, which accelerated the separation of photogenerated electrons and holes in the Zr-MOFs. It is believed that the synergistic effect of mechanical vibration and light irradiation significantly enhanced the photocatalytic performance of these composite membranes, making them promising candidates for sustainable hydrogen production and other photocatalytic applications.

Pollution from electromagnetic waves has prompted the development of high-performance electromagnetic wave (EMW) absorbers. However, single-component absorption materials cannot meet current performance requirements. Therefore, multi-component composites become the focus of research. Here, CoZn-based metal organic framework (CoZn-ZIF-L) nanosheets are synthesized and transformed into nitrogen-doped carbon-wrapped CoZn nanoparticles (CoZn@NC). Subsequently, a hydrothermal process was used to compound ultrasmall CuS nanoparticles on surface of the CoZn@NC to construct a strong interface coupling structure, effectively combining the dielectric properties of CoZn@NC and CuS. It is experimentally demonstrated that the optimized heterostructure exhibited significantly enhanced EMW absorption capacity, with a reflection loss (R_L) of −56.2 dB, a matching thickness of only 1.46 mm, and an effective absorption bandwidth (EAB, R_L ≤−10 dB) of 3.6 GHz. This work provides an efficient way to design high-performance EMW absorption materials with strong interface coupling.

SiOC-based ceramics are considered promising electromagnetic wave-absorbing materials because of their lightweight, high-temperature resistance, and heat insulation properties. Herein, SiOC@C ceramic nanospheres were prepared using a liquid-phase method combined with a polymer-derived ceramic (PDC) method, followed by heat treatment in N₂ and Ar atmospheres at different temperatures. The morphology, microstructure, phase composition, and electromagnetic wave absorption performance of the SiOC@C ceramic nanospheres were investigated in detail. The SiOC@C ceramic nanospheres obtained in the Ar atmosphere showed a minimum reflection loss (RL_min) of −67.03 dB, whereas the SiOC@C ceramic nanospheres obtained in the N₂ atmosphere exhibited an RL_min value of −63.76 dB. The outstanding electromagnetic wave absorption performance of the SiOC@C ceramic nanospheres was attributed to the synergistic effect between conductive loss, interfacial/defect polarization loss, multiple reflections, and scattering. Therefore, this research provides valuable insights into the design and fabrication of SiOC ceramic-based electromagnetic wave absorbers.

Two-dimensional (2D) transition metal carbides (MXene) possess attractive conductivity and abundant surface functional groups, providing immense potential in the field of electromagnetic wave (EMW) absorption. However, high conductivity and spontaneous aggregation of MXene suffer from limited EMW response. Inspired by dielectric–magnetic synergy effect, the strategy of decorating MXene with magnetic elements is expected to solve this challenge. In this work, zigzag-like Mo₂TiC₂–MXene nanofibers (Mo-based MXene (Mo–MXene) NFs) with cross-linked networks are fabricated by hydrofluoric acid (HF) etching and potassium hydroxide (KOH) shearing processes. Subsequently, Co-metal–organic framework (MOF) and derived CoNi layered double hydroxide (LDH) ultrathin nanosheets are grown inside Mo–MXene NFs, and the N-doped carbon matrix anchored by CoNi alloy nanoparticles formed by pyrolysis is firmly embedded in the Mo–MXene NFs network. Benefiting from synergistic effect of highly dispersed small CoNi alloy nanoparticles, a three-dimensional (3D) conductive network assembled by zigzag-like Mo–MXene NFs, numerous N-doped hollow carbon vesicles, and abundant dual heterogeneous interface, the designed Mo–MXene/CoNi–NC heterostructure provides robust EMW absorption ability with a reflection loss (RL) value of −68.45 dB at the thickness (d) of 4.38 mm. The robust EMW absorption performance can be attributed to excellent dielectric loss, magnetic loss, impedance matching (Z), and multiple scattering and reflection triggered by the unique 3D network structure. This work puts up great potential in developing advanced MXene-based EMW absorption devices.

Transition metal phosphides with metallic properties are a promising candidate for electrocatalytic water oxidation, and developing highly active and stable metal phosphide-based oxygen evolution reaction catalysts is still challenging. Herein, we present a facile ion exchange and phosphating processes to transform intestine-like CoNiP_x@P,N-C into lotus pod-like CoNiFeP_x@P,N-C heterostructure in which numerous P,N-codoped carbon-coated CoNiFeP_x nanoparticles tightly anchors on the 2D carbon matrix. Meanwhile, the as-prepared CoNiFeP_x@P,N-C enables a core-shell structure, high specific surface area, and hierarchical pore structure, which present abundant heterointerfaces and fully exposed active sites. Notably, the incorporation of Fe can also induce electron transfer in CoNiP_x@P,N-C, thereby promoting the oxygen evolution reaction. Consequently, CoNiFeP_x@P,N-C delivers a low overpotential of 278 mV (vs RHE) at a current density of 10 mA cm⁻¹ and inherits excellent long-term stability with no observable current density decay after 30 h of chronoamperometry test. This work not only highlights heteroatom induction to tune the electronic structure but also provides a facile approach for developing advanced and stable oxygen evolution reaction electrocatalysts with abundant heterointerfaces.