In situ TPR removal: a generic method for fabricating tubular array devices with mechanical and structural soundness, and functional robustness on various substrates

Abstract

Wire array templates have been utilized for fabricating various three-dimensional tubular structure devices, such as solar cells, batteries and supercapacitors, as well as electronic and photonic devices. It is necessary to remove the templates by using post-treatments such as wet chemical etching, decomposition, or Kirkendall approaches. However, it remains a challenge to ensure tubular structure integrity, mechanical soundness, and chemical purity during the template removal process, which affects the functional robustness of enabled tubular structure array devices. In this work, by utilizing ZnO nanorod array devices as templates and temperature programmed reduction (TPR) as the removal method, nanotube array devices made of various functional oxides have been directly converted with well-retained uniformity, structure and mechanical soundness, and chemical homogeneity on both two-dimensional (2D) planar and three-dimensional (3D) monolith device substrates. The successful examples range from binary metal oxides such as fluorite CeO₂ to complex oxides like perovskite La_0.8Sr_0.2CoO₃ (LSCO). This TPR removal method is generic, simple and rationally controllable, and can be easily expanded to the preparation of other oxides and non-oxide tubular structure devices regardless of the interfaced device substrate geometry. As a demonstration, the enabled CeO₂ nanotube array devices could function as good high-temperature O₂ sensors and active photocatalytic devices with good robustness.