Boric Acid-assisted Construction of Polyoxometalate/Lactose-derived Defective Porous Carbon for Highly Efficient Microwave Absorption

doi:10.15541/jim20260113

Abstract

Abstract:

Developing lightweight, broadband, and highly efficient microwave absorption materials is of great significance for electromagnetic protection in complex environments. In this study, a series of composition-tunable composites (WX@LC, X = Mn, Fe, Co) consisting of polyoxometalate (POM)-derived metal tungstate, tungsten oxide, and porous carbon were designed. Using lactose as the carbon source and transition metal-substituted POMs as inorganic precursors, the composites were successfully synthesized via a facile one-step air pyrolysis strategy with boric acid as a pore-forming agent. Microstructural analysis reveals that introducing the POM precursor precisely constructs a high concentration of oxygen vacancies and rich heterogeneous interfaces within the highly interconnected 3D porous carbon network. Furthermore, a dual-phase heterogeneous interface between MnWO₄ and WO_2.83 is exclusively observed in the Mn-doped WM@LC sample. This unique multiple heterogeneous structure induces strong interfacial polarization while maintaining moderate conduction loss, which effectively optimizes impedance matching. Electromagnetic measurements demonstrate that WM@LC exhibits optimal microwave absorption performance. At a low filler loading of 15% (in mass), it achieves a minimum reflection loss (RL_min) of -73.13 dB at a thickness of 4.11 mm, and a maximum effective absorption bandwidth (EAB_max) of 6.64 GHz at 2.18 mm, fully covering the Ku band. This work offers an effective pathway for designing the microstructure of carbon-based microwave absorbers and provides a reliable reference for applying POM derivatives in electromagnetic protection.

Key words: polyoxometalate, microwave absorption, bio-derived carbon, heterointerface

CLC Number:

TB34

SHI Jinzhao, ZHU Meiling, ZHENG Qi, WANG Lianjun, JIANG Wan. Boric Acid-assisted Construction of Polyoxometalate/Lactose-derived Defective Porous Carbon for Highly Efficient Microwave Absorption[J]. Journal of Inorganic Materials, 2026, 41(10): 1470-1480.

Figures/Tables 15

Fig. 1 Schematic diagram of the experimental procedure for preparing WX@LC composites by boric acid template-assisted pyrolysis

Fig. 2 TEM images and corresponding elemental distributions of WX@LC composites (a, d, g) TEM images; (b, e1, e2, h1, h2) HRTEM images; (c, f, i) STEM images and corresponding EDS elemental mappings; (a-c) WM@LC; (d, e1, e2, f) WF@LC; (g, h1, h2, i) WC@LC

Fig. 3 Characterization of phase structure and surface chemical composition of the samples (a) XRD patterns; (b) Raman spectra; (c) XPS full spectra; (d-f) High-resolution XPS spectra of (d) C1s, (e) O1s and (f) W4f, which reveal the coexistence of oxygen vacancies and multiple valence states of tungsten. Colorful figures are available on website

Fig. 4 Microwave absorption performance characterization of the samples (a1-d1) Three-dimensional reflection loss plots; (a2-d2) Corresponding two-dimensional RL contour plots; (a3-d3) Impedance matching Smith chart. Colorful figures are available on website

Fig. 5 Comparison of electromagnetic parameters, dielectric loss mechanisms, and microwave absorption performance of the samples (a) Real part of complex permittivity (ε'); (b) Imaginary part of complex permittivity (ε''); (c) Dielectric loss tangent (tanδE); (d) Attenuation constant (α); (e) Conduction loss (εc''); (f) Polarization relaxation (εp''); (g-j) Cole-Cole curves; (k) Conductivity histogram; (l) Comparison of microwave absorption performance. Colorful figures are available on website

Fig. 6 Microwave mechanism of WM@LC

Fig. S1 Comparison of experimental and simulated XRD patterns for W18Mn, W18Fe, and W18Co samples

Fig. S2 SEM images of the samples (a1-d1) Low-magnification SEM images of LC, WM@LC, WF@LC and WC@LC; (a2-d2) High-magnification SEM images of the corresponding samples

Fig. S3 TEM image and C elemental distribution of LC

Fig. S4 Pore structure characterization of the samples (a1-d1) Nitrogen adsorption-desorption isotherms; (a2-d2) Pore size distribution curves

Fig. S5 XRD pattern of SiW12@LC sample

Fig. S6 High-resolution XPS spectra of the samples (a) Mn2p; (b) Fe2p; (c) Co2p

Fig. S7 EPR spectra of WX@LC

Fig. S8 Complex permeability and magnetic loss characteristics for samples (a) Real part of complex permeability (μ'), (b) Imaginary part of complex permeability (μ''), (c) Magnetic loss tangent (tanδM)

Table S1 Comparison of the overall performance of WM@LC with recent bio-derived carbon/advanced carbon-based microwave absorbing materials

Sample	RL_min/dB	Thickness/mm	EAB_max/GHz	Thickness/mm	Loading/% (in mass)	Ref.
FCCMT	-39.08	1.9	6.85	1.9	30	[55]
CoNi-MOF-Se-500	-51.1	1.8	4	1.8	25	[52]
C/Fe₃O₄	-40.1	2	5.12	2	50	[57]
WCA/BiCo@NC	-50.92	1.4	4.88	1.4	40	[53]
HCMs-900	-57.5	2.5	5.76	1.8	15	[22]
NiS/Co₃S₄/NiCoQCNTs/NC	-75.9	2.6	4.8	2.6	30	[56]
FCM	-52.59	1.92	6.04	2.2	30	[54]
NiO/NiFe₂O₄/Ni/Ni₃Fe@BC	-67.44	2.773	6.7	1.754	25	[51]
Fe-BBCN/Ti₃C₂T_x	-46.8	2	4.2	1.5	30	[58]
HPC-650	-49.96	1.5	6.46	2.4	30	[59]
PNBC/CoFe₂/CoFe₂O₄	-52.21	1.44	4.32	1.44	30	[60]
WM@LC	-73.13	4.11	6.64	2.18	15	This work

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