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Porous flower nickel oxide@polyaniline (NiO@PANI) composites as excellent microwave absorption (MA) materials in the X-band were synthesized via a two-step strategy in this work. The porous NiO flower is uniformly dispersed and homogeneous in particle size after Ostwald ripening process. Coating conductive PANI on the surface of porous NiO microspheres could improve interfacial polarization and dielectric loss property that will lead to a great improvement of MA properties. Electromagnetic (EM) parameters of NiO@PANI composites with different NiO contents were investigated by a vector network analyzer and the reflection loss (RL) values with varied thickness were also calculated. The results showed that the effective absorption bandwidths ($\mathrm{\text{RL}}<-10$dB) of all NiO@PANI composites can cover the whole X-band. Especially, the NiO@PANI${}_{0.1}$ composite is able to attenuate microwave energy in the X-band with the thickness of 2.5mm. The NiO@PANI${}_{0.2}$ has a maximum RL of $-32.8$dB at 10.1GHz and the effective absorption bandwidths cover 4.64GHz (11.12–15.76GHz) at 2.0mm. The excellent MA absorption performance may be ascribed to the polarization effect, dielectric loss and structure of porous flower-like NiO@PANI. Our work confirms that the synthesized NiO@PANI composite is an attractive candidate as a highly efficient MA material in the X-band.

Improving the efficiency of glucose oxidation reaction (GOR) is extremely important to build high performance nonenzymatic glucose sensors and fuel cells. In this work, we designed a novel binary ($\alpha$–$\beta )$ NiS/PANI nanorods electrocatalyst with polyaniline (PANI) as the substrates and binary ($\alpha$–$\beta )$ NiS nanoparticles dispersing on the PANI nanorods. The as-prepared NiS/PANI nanorods were characterized by XRD, XPS and SEM. The electrochemical performance of NiS/PANI nanorods was evaluated by cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy, which showed highly improved catalytic efficiency for GOR. When used as anodic catalysts in nonenzymatic glucose fuel cells, NiS/PANI nanorods displayed much higher power density of 1343.39 $\mu \mathrm{\text{W}}\cdot {\mathrm{\text{cm}}}^{-2}$ with an open circuit voltage of 0.84 V. NiS/PANI/NiS nanorods also presented excellent nonenzymatic sensing performance for glucose detection including a wide sensitivity of 682.21 $\mu \mathrm{\text{A}}\cdot {\mathrm{\text{mM}}}^{-1}\cdot {\mathrm{\text{cm}}}^{-2}$ (10–9000 $\mu$M) and the low detection limit of 3.33 $\mu$M ($\mathrm{\text{S/N}}=3$). The obviously improved electrochemical properties of NiS/PANI/NiS nanorods for GOR may be due to the synergistic effect of binary ($\alpha$–$\beta )$ NiS and PANI nanorods.

This is a comparative study of supercapacitor performance of CeO₂/PANI composite electrode prepared by two different synthesis methods, namely, in situ polymerization and solution mixing. The chemical composition of materials was confirmed by X-ray diffraction (XRD). The electrochemical studies such as cyclic voltammetry (CV), charge–discharge, electrochemical impedance and cyclic test of the composite were studied in two symmetrical electrode systems in an aqueous electrolyte medium. The CeO₂/PANI (CP10) composite prepared by in situ polymerization has resulted in better specific capacitance than solution mixing in an aqueous electrolyte (0.5M H₂SO₄) with the capacitance value of 240F/g at 0.5A/g. The in-situ polymerization method evenly spreads polyaniline (PANI) all over the cerium oxide (CeO₂) material and reduces charge transfer resistance ($R_{\mathrm{\text{ct}}}$) which is lacking in the solution mixing method. After 4000 cycles at 5A/g, the CP10 composite retained 72.8% of capacitance retention and energy density of 33.33Wh/Kg at power density of 249.87W/Kg.