Tobacco mosaic virus-templated hierarchical Ni/NiO with high electrochemical charge storage performances

Three-dimesional hierarchical electrodes exhibiting multi-dimensional geometries provide exceptional advantages for advanced energy storage performance. In this work, we report the fabrication and characterization of biotemplated hierarchical-Ni/NiO electrodes enabled by thermal oxidation of electroless Ni-coated Tobacco mosaic viruses (TMVs) self-assembled on Au-coated Si micropillar arrays. Uniform NiO formation on the metallized TMV nanoscaffolds is characterized by XPS and STEM-EELS analysis and the electrochemical performance was characterized in 2 M KOH solution. The hierarchicalNi/NiO show a 3.3 and 32.6 times increase in areal capacity (81.4 mAh cm ) compared to solely nanostructured (24.3 mAh cm ) and planar electrodes (2.5 mAh cm ), respectively. The NiO electrodes show interesting capacity increase phenomenon during the initial activation cycles. Based on our experimental analysis, it is attributed to both an increase in active surface area/mesoporosity and NiO content during the initial charge/discharge cycles, and the increase has dependence on electrode geometry. The hierarhical-Ni/NiO electrode exhibit excellent cycle stability up to 1500 charge/discharge cycles at 2 mA cm 2 with no capacity fading. Based on the results, the hierarchical-Ni/NiO is a promising candidate for advanced electrochemical energy storage devices. ã 2016 Elsevier Ltd. All rights reserved.