Facile preparation of aligned NiO nanotube arrays for electrochromic application

Tailor-made nanotube arrays possess great potential for developing high-performance optical and electrochemical energy storage devices. Herein, we report a facile ZnO template-assisted hydrolysis method to fabricate aligned NiO nanotube arrays. The obtained NiO nanotubes are large-area and open-ended tube structures with stacked nanoparticle walls, which can shorten the diffusion distance of ions and increase surface area. As an electrochromic material, the aligned NiO nanotube arrays exhibits excellent electrochromic performances, including a larger transmittance modulation (78.5% at 550 nm), fast switching responses (3.92 s for coloration and 3.43 s for bleaching) and high CE (51.8 cm² C^{− 1} at 550 nm). Moreover, the aligned NiO nanotube arrays also depict a high stability and durability after 1000 cycles. It is also expected that this synthetic method can be extended to scale-up production of the aligned NiO nanotube arrays.