Fabrication of CoNi alloy hollow-nanostructured microspheres for hydrogen storage application

• Published in: Journal of nanoparticle research : an interdisciplinary forum for nanoscale science and technology 2013-07, Vol.15 (7), p.1-11, Article 1768
• Main Authors: Rafique, M. Yasir, Pan, Liqing, Iqbal, M. Zubair, Rafi-ud-din, Qiu, Hongmei, Farooq, M. Hassan, Guo, Zhengang, Ellahi, Mujtaba
• Format: Article
• Language: English
• Subjects: Anisotropy; Characterization and Evaluation of Materials; Chemical synthesis methods; Chemistry and Materials Science; Coercive force; Coercivity; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Fabrication; Growth from solutions; Hydrogen; Hydrogen storage; Inorganic Chemistry; Lasers; Low temperature; Low-dimensional structures (superlattices, quantum well structures, multilayers): structure, and nonelectronic properties; Materials Science; Methods of crystal growth; physics of crystal growth; Methods of nanofabrication; Microspheres; Nanomaterials; Nanoparticles; Nanoscale materials: clusters, nanoparticles, nanotubes, and nanocrystals; Nanostructure; Nanotechnology; Nickel; Optical Devices; Optics; Photonics; Physical Chemistry; Physics; Research Paper; Saturation (magnetic); Storage capacity; Structure of solids and liquids; crystallography; Surface area; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties)
• ISSN: 1388-0764; 1572-896X
• DOI: 10.1007/s11051-013-1768-1

Co 20 Ni 80 hollow-nanostructured microspheres are prepared by template-free hydrothermal method at low temperature (150 °C). The prepared CoNi nanostructures have face-centered cubic crystal lattice. Williamson–Hall analysis shows crystallite size of 55.5 nm and microstrain of 0.00265. Elemental mapping confirms the uniform distribution of Co and Ni atoms in sample. The size of hollow spheres is in the range of 1–3 μm which increase to 10 μm by increasing the reaction time. A stepwise growth mechanism based on time-dependent experiment is briefly described. The X-ray photoelectron spectroscopy analysis suggests the only metallic chemical state of Co and Ni in sample (no surface oxidation). The specific surface area of 80.56 m 2 /g is obtained for 2 μm hollow sphere. The Co 20 Ni 80 hollow-nanostructured microsphere shows 0.92 mass% hydrogen absorption and 81 % release of stored hydrogen. Hydrogen storage is attributed to crystal defects. The effects of morphology and surface area on hydrogen storage capacity and response are described. The saturation magnetization of 72.1 emu/g and coercivity of 157.21 Oe are observed for 2 μm hollow spheres. However, saturation magnetization of 77.5 emu/g and coercivity of 120 Oe are observed for 10 μm hollow spheres. The enhanced coercivity is related to surface and shape anisotropy due to hollow structure.