3D-Hierarchical porous nickel sculptured by a simple redox process and its application in high-performance supercapacitors†
Porous metals with a cellular architecture have attracted considerable attention for a diverse range of applications. Extensive efforts have been devoted to exploring cost-effective ways to create porous metals. Here we propose a novel approach for the fabrication of micron porous Ni metals through a redox process in a CH4–O2 gas mixture at 750 °C. The multiple redox cycles at high temperatures facilitate a rapid reconstruction of Ni atoms, producing a cellular architecture. This process is simple and clean, avoiding the use of precious metals and templates. The redox process is applicable to the creation of porous architectures (from surface texturing to 3D cellular structures) on a Ni sheet and a unique hierarchical porous architecture on Ni foam. Furthermore, nanocrystalline MnO2 is successfully coated on a micron porous Ni foam (MPNF) to form a supercapacitor electrode. The micron porous architectures of the MPNF–MnO2 electrode enhance not only the electrochemical performance but also the mechanical integrity and robustness, leading to ultrahigh capacitance and excellent cycling stability. More importantly, the strategy of micron-sculpturing of metals using a redox process is readily applicable to other metal systems for the fabrication of cellular metals and alloys for a variety of applications, including catalysis, energy storage and conversion, and chemical sensing.