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Electrochimica Acta, Vol.286, 1-13, 2018
Support-induced morphology and content tailored NiCo2O4 nanostructures on temperature-dependent carbon nanofibers with enhanced pseudocapacitive performance
Direct anchorage of metal oxides on carbon nanofibers is challenging, and simultaneous modulation of morphology, content and thus pseudocapacitance of anchored metal oxides has never been achieved. Herein we report direct anchorage of NiCo2O4 nanostructures with tailored morphology, content and pseudocapacitance, on temperature-dependent carbon nanofibers (CNEs), which are derived from zinctrimesic acid fibers at a temperature no more than 600 degrees C. The temperature-dependent CNEs, including CNF-390, CNF-450 and CNF-600, were first investigated by SEM, TG, FT-IR, XPS and Boehm titration studies. It is found that their textural property, thermal stability and surface functionality vary depending on pyrolysis temperature. As a result, the morphology, content and thus the pseudocapacitance of anchored NiCo2O4 nanostructures are also temperature-dependent. It is revealed that as increasing the pyrolysis temperature, the shape of NiCo2O4 is transformed from embedded nanoparticles to exposed nanosheets while its content decreases from 95 to 55 wt%. The resultant NiCo2O4/CNF-450, bearing highly dispersed nanosheets and optimized NiCo2O4 content (72.6%), exhibits the best capacitive performance with a large specific capacitance of 870 F g(-1) at a scan rate of 1 mV s(-1) , and a high energy density of 39.3 Wh kg(-1) in the case of power density of 300 W kg(-1) . The elaborately fabricated NiCo2O4/CNF-450 also shows excellent charge-discharge stability (with the capacity retention ratio of 85.7% after 5000 cycles). The improved accessibility for more pseudocapacitive NiCo 2 0 4 nanosheets, as well as the strong interaction between NiCo2O4 and carbon nanofiber, should be responsible for the enhanced capacitive performance of NiCo2O4/CNF-450. This research also provides the concept of support-induced modulation of property and pseudocapacitive performance of anchored metal oxides. (C) 2018 Elsevier Ltd. All rights reserved.