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Hollow mesoporous PPy@MnO 2 composites were successfully synthesized by a low-temperature redox reaction. The synthesized hollow mesoporous PPy@MnO 2 electrode has outstanding electrochemical properties with a specific capacitance of 713 F g−1 at 1 A/g and a 92% retention rate after 5000 cycles at 4 A/g. The asymmetric supercapacitor constructed using PPy@MnO 2 as the positive electrode material achieved a high energy density of 40.8 Wh kg−1 at a power density of 720 W kg−1, and the capacitance retention rate can be maintained at 90.5% after 5000 charge/discharge cycles at 5 A/g. [Display omitted] • Hollow mesoporous PPy@MnO 2 composite were successfully synthesized by a low-temperature redox reaction. • PPy@MnO 2 composite with hollow mesoporous core–shell structure had good performance in supercapacitor. • The asymmetric supercapacitor devices assembled with PPy@MnO 2 composite possess remarkable cycling stability (90.5 % after 5000 cycles at 5 A g−1) and high energy density (40.8 Wh kg−1 at the power density of 720 W kg−1). In this work, hollow mesoporous PPy microspheres were prepared by using mesoporous SiO 2 as a hard template, and hollow mesoporous PPy@MnO 2 composites were successfully synthesized by a low-temperature redox reaction. The unique heterogeneous structure can realize the complementary advantages of the two materials. PPy can be used as a template to support the whole structure, and the design of the hollow structure will further buffer the volume change during cycling. In addition, the mesoporous structure will further increase its specific surface area and porosity, thereby enhancing the stability of its overall structure and internal electron transport, and significantly increasing the number of active sites. Thus, the synthesized hollow mesoporous PPy@MnO 2 electrode has outstanding electrochemical properties with a specific capacitance of 713 F g−1 at 1 A g−1 and a 92 % retention rate after 5000 cycles at 4 A g−1. The asymmetric supercapacitor constructed using PPy@MnO 2 as the positive electrode material achieved a high energy density of 40.8 Wh kg−1 at a power density of 720 W kg−1. This work inspires a simple idea for designing hollow mesoporous nanocomposite electrodes with excellent electrochemical performance and provides a high-performance supercapacitor material for its practical applications. [ABSTRACT FROM AUTHOR]

Fe 3 O 4 @PPy@MnO 2 ternary core-shell nanospheres are synthesized by facile solvothermal, in-situ polymerization, and redox reactions.The nanocomposite exhibits excellent electrochemical performance with specific capacitance of 751F g−1 at 1 A/g and remarkable cycling stability (87.0% capacitance retention after 5000 cycles at 4 A/g). The asymmetric supercapacitor devices assembled with Fe 3 O 4 @PPy@MnO 2 nanocomosite possess remarkable cycling stability (95.2% after 5000 cycles at 5 A/g) and high energy density (71.3 Wh kg−1 at the power density of 750 W kg−1). [Display omitted] • Fe 3 O 4 @PPy@MnO 2 ternary core-shell nanospheres are synthesized. • The electrode exhibits high specific capacitance and good cycling stability. • The asymmetric supercapacitor devices possess high energy density. The rapid development of supercapacitors has led to increasing demand for electrode materials with excellent electrochemical properties. In this study, Fe 3 O 4 @PPy@MnO 2 nanocomposites with porous core and double-shell layers were successfully synthesized and utilized as supercapacitor electrode materials. Specifically, a dense PPy coating is formed on the porous Fe 3 O 4 surface to ensure high structural stability, and a MnO 2 shell layer could be easily introduced on the PPy surface through the redox reaction between PPy and KMnO 4. The prepared composite electrode material has the advantages of high specific surface area, short diffusion distance of electrolyte ions, good electron transfer, and fast and reversible Faraday reaction. The Fe 3 O 4 @PPy@MnO 2 electrode not only exhibits high specific capacitance (751F g−1 at 1 A/g), but also exhibits excellent cycling stability (87.0 % capacitance retention after 5000 cycles at 4 A/g). This is owing to the synergistic effect of the porous Fe 3 O 4 core, the dense PPy coating, and the MnO 2 nanosheet shell. Furthermore, the asymmetric supercapacitor devices assembled with Fe 3 O 4 @PPy@MnO 2 nanocomosite possess remarkable cycling stability (95.2 % after 5000 cycles at 5 A/g) and high energy density (71.3 Wh kg−1 at the power density of 750 W kg−1). These results demonstrate the great potential of Fe 3 O 4 @PPy@MnO 2 nanocomposites with porous cores and double shells as electrode materials for high-performance supercapacitors. [ABSTRACT FROM AUTHOR]

A 3D macroporous stainless steel fiber felt (SSFF) is used as base material and a simple water bath method is adopted to directly load Pd nanocatalysts on SSFF to fabricate the air cathode of microbial fuel cells (MFCs). The optimum Pd loading is explored on the basis of the optimized PVP additive amount and reaction temperature. To attain a high ORR activity, a conductive carbon black filling layer is added into the 3D pores of Pd-SSFF. A series of physical and electrochemical tests are conducted to characterize the morphology, chemical composition and oxygen reduction activity and then the obtained cathodes are installed in MFCs for electricity production verification. The results show that the Pd-SSFF cathode at a Pd loading of 0.5 mg cm−2 (Pd-SSFF-0.5) achieves high output voltage and power density (492.65 mV, 390.79 mW m−2) which are comparable to the conventional Pt/C electrode (504.80 mV, 405.47 mW m−2). Furthermore, with Pd-SSFF-0.5 cathode the high-voltage platform duration of MFC in one operation cycle is 2.79 times of that of Pt/C electrode. Excellent mechanical properties (high pressure and corrosion tolerance), high electric energy output and simple fabrication prove it is an efficient strategy to improve the overall performance of MFCs using the obtained cathodes. • 3D macroporous SSFF is proposed as base material in air cathode. • Pd nanocatalysts is loaded directly on SSFF with the simple water bath method. • This loading method can replace the complex preparation process of powder catalysts. • Filling carbon black into the 3D pores of Pd-SSFF helps improving ORR performance. • Excellent mechanical properties and high electric output are achieved by Pd-SSFF cathodes. [ABSTRACT FROM AUTHOR]