Enhanced Li storage performance of ordered mesoporous MoO2via tungsten doping

Xiangpeng Fang, Bingkun Guo, Yifeng Shi, Bin Li, Chunxiu Hua, Chaohua Yao, Yichi Zhang, Yong-Sheng Hu, Zhaoxiang Wang, Galen D. Stucky, Liquan Chen
2012 Nanoscale  
Experimental Mesoporous W-doped MoO 2 was obtained using mesoporous silica KIT-6 as a hard template. PTA and PMA (W PTA /(W PMA +W PTA ) = 0.25) were adopted as the tungsten and molybdenum sources respectively and filled into the mesopore of KIT-6 template. The prepared precursors@template composite was then heated up to 700º C at a rate of 5º C min -1 in a mixed gas flow of 10% H 2 and 90% Ar. During this treatment, the PTA and PMA precursors decomposed and the tungsten and molybdenum atoms
more » ... e reduced in-situ from 6+ to 4+, forming crystalline dioxide product inside the mesopore of the KIT-6 template. Mesoporous silica template was removed using 4 wt% HF as etchant, and highly ordered mesoporous crystalline W-doped MoO 2 was collected as the final product. Meanwhile, for comparison, mesoporous MoO 2 was synthesized in the same way which has been reported in our earlier paper. Chemicals: Triblock poly (ethylene oxide)-b-poly (propylene oxide)-b-poly (ethylene oxide) copolymer Pluronic P123 (M w = 5800, EO 20 PO 70 EO 20 ), n-butanol, tetraethyl orthosilicate (TEOS), phosphotungstic acid H 3 PW 12 O 40 •xH 2 O (PTA), phosphomolybdic acid H 3 PMo 12 O 40 •xH 2 O (PMA), hydrochloride acid (38 wt%) and hydrofluoric acid (48 wt%) were purchased from Aldrich Chemical Inc.. Micro-sized WO 2 was obtained from Aldrich Chemical Inc. Premixed 10% hydrogen diluted with 90% argon gas were purchased from Praxair, Inc.. All chemicals were used as received without any further purification. Millipore water was used in all experiments. Synthesis of KIT-6 hard template material: Mesoporous silica KIT-6 was prepared according to the literature report and used as the hard template in our synthesis: 23.5 g of triblock copolymer P123 was dissolved in the mixture of 850 mL of water and 38.0 mL of 38 wt.% HCl with stirring overnight to get a clear solution. The solution was heated to 35 o C and then 23.5 g of n-butanol was added. After 2 h stirring, 48.0 g of TEOS was poured in with rigorously stirring, and the mixture was kept at the same temperature for another 24 h. The above mixture was then transferred into a Teflon lined stainless steel autoclave and heated up to 110 º C for 2 days for hydrothermal treatment. The white solids were recovered by filtration and dried in a 65º C oven. Thereafter, the products were calcined at 500º C for 2 h with a heating rate of 1.5º C min -1 in air to remove the P123 surfactant. Synthesis of mesoporous W-doped MoO 2 : 4.2 g of precursor, composed of PTA and PMA with weight ratio 25:75, was added into 20 mL of ethanol in an open crucible, leading to a homogenous clear yellow solution. 1.0 g of mesoporous silica KIT-6 hard template was then added into the solution under stirring at room temperature in a fume Electronic Supplementary Material (ESI) for Nanoscale This journal is
doi:10.1039/c2nr12017h pmid:22294160 fatcat:tqe5xxovivhxrefzzqp2imzqza