Wang Xiaoxia,Yu Jianhua,Dong Hongzhou,Yu Mingxun,Zhang Baoqin,Wang Wen,Dong Lifeng
In this work, metal oxide (MnO 2 , SnO 2 and Co 3 O 4 )–graphene composite materials were successfully prepared via different synthesis methods. Uniform metal oxide nanoparticles were well dispersed on graphene sheets, and transmission electron microscopy characterizations showed that the average sizes of MnO 2 , SnO 2 , and Co 3 O 4 particles were about 60, 5, and 10 nm, respectively. Reflection losses of graphene composites and pure graphene were systematically evaluated between 2 and 18 GHz, which revealed that all composites exhibited enhanced microwave absorption properties compared to pure graphene. The minimum reflection losses of MnO 2 -graphene, SnO 2 –graphene, and Co 3 O 4 –graphene composites with a thickness of 2.0 mm were −20.9, −15.28, and −7.3 dB at the frequency of 14.8, 15.94, and 9.6 GHz, respectively, whereas −4.5 dB for pure graphene. The enhanced absorption ability probably originated from the combined advantage of metal oxide particles and graphene, which proved beneficial to improve the impedance matching of permittivity and permeability. Besides, the intrinsic characteristics of MnO 2 , SnO 2 , and Co 3 O 4 nanoparticles, the interface between nanostructured metal oxides and graphene sheets, and the multi-dielectric relaxation processes are all influence factors to improve the properties of microwave absorption.
Promotion of the catalytic efficiency and reduction of the usage amount of Pd are crucial to developing effective and low-cost catalysts for catalytic reduction of organic aromatic nitro pollutant compound at present. Herein, we report a hybrid material of ultrafine Pd nanocrystals (PdNCs) grown on an excellent support of SnO2-decorated graphene nanosheets (SnO2-GNS) for a highly efficient reduction of a representative aromatic nitro compound (4-nitrophenol). The supporting material of SnO2-GNS was prepared simply by one step of homogeneous reaction with a positively charged polymer as stabilizer and active site for absorption of the PdNCs precursor. Transmittance electronic images demonstrate that the PdNCs are densely and well covered on the SnO2-GNS with a uniform size of 3.4 nm. This nanohybrid exhibits the fastest reduction time (4 minutes) compared to other controlled materials. Moreover, it shows high kinetic responses with an apparent kinetic rate constant (kapp) of 2.03 × 10−2 s−1 and turnover frequency (TOF) of 1.70 s−1. The cycle performance (10 times) experiments demonstrate that this nanohybrid also displays a good anti-poisoning capability. Thanks to the ultrafine PdNCs, this as-prepared PdNCs/SnO2-GNS nanohybrid may have broad potential in other catalytic fields, for example, organic synthesis, fuel cells and electrochemical biosensors.
The design of high comprehensive properties structural supercapacitors requires advanced electrode materials with suitable porous structure for ion diffusion , as well as unique solid electrolyte owning excellent mechanical property under high-pressure compression. Herein, we presented a novel structural supercapacitor cell constructed by graphene-coated nickel foam decorated with SnO 2 electrode and PAM–Portland cement electrolyte. It was found that the RGO/SnO 2 -1 electrode displays superior electrochemical performance with the highest areal capacitance of 0.374 F cm −2 at the current density of 1 mA cm −2 , good cycle stability, and capacitance retention rate can reach 80.4% after 1000 cycles. Polymer-inorganic cement electrolyte was prepared by synchronous reaction at room temperature. The resulting structural supercapacitor cell showed relatively high electrochemical and mechanical properties . The areal capacitance was as high as 61.0 mF cm −2 at the current density of 0.1 mA cm −2 . The excellent electrochemical performance combined with high mechanical comprehensive properties makes it a promising candidate in civil engineering applications.
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