Article pubs.acs.org/cm
Cite This: Chem. Mater. 2018, 30, 2924−2929
Facile Synthesis of Highly Porous Metal Oxides by Mechanochemical Nanocasting Weiming Xiao,†,# Shize Yang,§,# Pengfei Zhang,*,‡,∥ Peipei Li,‡ Peiwen Wu,‡ Meijun Li,⊥ Nanqing Chen,⊥ Kecheng Jie,⊥ Caili Huang,‡ Ning Zhang,*,† and Sheng Dai*,‡,⊥ †
Institute of Applied Chemistry, College of Chemistry, Nanchang University, Nanchang, Jiangxi 330031, P. R. China Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, United States § Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, United States ∥ School of Chemistry and Chemical Engineering, Shanghai Jiao Tong University, Shanghai 200240, P. R. China ⊥ Department of Chemistry, University of Tennessee, Knoxville, Tennessee 37996, United States
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S Supporting Information *
ABSTRACT: Metal oxides with high porosity usually exhibit better performance in many applications, as compared with the corresponding bulk materials. Template-assisted method is generally employed to prepare porous metal oxides. However, the template-assisted method is commonly operated in wet conditions, which requires solvents, soluble metal oxide precursors, and a long time for drying. To overwhelm those drawbacks of the wet procedure, a mechanochemical nanocasting method is developed in the current work. Inspired by solid-state synthesis, this strategy proceeds without solvents, and the ball milling process can enable pores replicated in a shorter time (60 min). By this method, a series of highly porous metal oxides were obtained, with several cases approaching the corresponding surface area records (e.g., ZrO2, 293 m2 g−1; Fe2O3, 163 m2 g−1; CeO2, 211 m2 g−1; CuOxCeOy catalyst, 237 m2 g−1; CuOx-CoOy-CeOz catalyst, 203 m2 g−1). Abundant nanopores with clear lattice fringes in metal oxide products were witnessed by scanning transmission electron microscopy (STEM) in high angle annular dark field (HAADF). By combination of mechanochemical synthesis and nanocasting, current technology provides a general and simple pathway to porous metal oxides.
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INTRODUCTION Embedding porosity into metal oxides can significantly advance their performance in many applications such as catalysis, sensors, microelectronics, photovoltaics, and biomedicines. It is understandable since larger active surfaces, faster mass transfer, and higher storage volume can be expected in porous metal oxides.1−6 The porous metal oxides are usually prepared by template-assisted processes, which proceed via either soft- or hard-templating methods.7−11 For the soft-templating method, self-assembly between metal precursors and block copolymers results in ordered organic−inorganic mesophases,11−13 followed by calcination to form crystalline metal oxides at the same time removing organic templates. The soft-templating approach, with membrane intermediates aging from several days to one month, is time-consuming; meanwhile, this technology is limited to porous metal oxides with low crystalline temperature (e.g.,
