As anode materials for lithium ion batteries, two three dimensionally ordered macroporous TiO 2 , one with disordered inter-particle mesopores formed by the aggregation of nanoparticles (3DOM) and another with inner-particle mesopores generated by a surfactant templating strategy (3DOMM), have been synthesized using poly(styrene-methyl methacrylate-3-sulfopropyl methacrylate potassium) (P(St-MMA-SPMAP)) spheres as a hard template and their electrochemical properties are compared. SEM and TEM observations reveal that both 3DOM TiO 2 and 3DOMM TiO 2 have well-ordered macropores and interconnected macropore walls with a regular periodicity. 3DOMM TiO 2 demonstrates a specific surface area of 139 m 2 g À1 , which is higher than that of 3DOM TiO 2 (99 m 2 g À1 ) due to the smaller crystallite size and inner-particle mesopores. The electrolyte adsorption results show that both 3DOM TiO 2 and 3DOMM TiO 2 have similar adsorption capacities despite a difference in the surface area. Electrochemical impendence spectroscopy analysis shows that 3DOMM TiO 2 has a lower charge transfer resistance and faster Li + diffusion coefficient than 3DOM TiO 2 . Moreover, both 3DOM TiO 2 and 3DOMM TiO 2 possess excellent initial capacity of 248 mA h g À1 and 235 mA h g À1 at 0.2 C and 208 mA h g À1 and 202 mA h g À1 at 1 C, respectively. The reversibility study demonstrates that the 3DOMM TiO 2 displays higher cycling capacity, superior rate behavior and higher Coulombic efficiency because the higher surface area provides more active sites and the presence of the inner-particle mesopores in the walls of macropores serve as a bicontinuous transport path and affords a shorter path length for diffusion of Li ions compared with the 3DOM TiO 2 and its crystallite aggregated mesopores. The reversible capacity of 106 mA h g À1 observed for the 3DOMM TiO 2 can be retained after 200 charge-discharge cycles at a relatively high current rate of 4 C. This cycle stability performance can be equally attributed to the crystallite size and inner-particle mesopores in the 3DOMM TiO 2 . Moreover, the existence of a bicontinuous porous structure in the 3DOMM TiO 2 can further enhance the lithium insertion/extraction capacity at high rates. We believe that this study can shed light on the 3DOMM structure as a promising material for highly enhanced performance in lithium ion batteries.
We demonstrate an alkali modification process to produce highly dispersed ultrafine Pt nanoclusters with metallic Pt 0 and oxidized Pt 2+ species as co-catalyst anchored on nanosheet-constructed yolk-shell TiO 2 (NYTiO 2-Pt) acting as light harvesting reactor for highly efficient photocatalytic H 2 production. Benefiting from the high surface area, highly dispersed ultrafine Pt nanoclusters (~0.6 nm) with Pt 0 and Pt 2+ species and special nanosheet-constructed yolk-shell structure, this novel light harvesting reactor exhibits excellent performance for photocatalytic H 2 production. The NYTiO 2-Pt-0.5 (0.188 wt% Pt) demonstrates an unprecedentedly high H 2 evolution rate of 20.88 mmol h-1 g-1 with excellent photocatalytic stability, which is 87 times than that of NYTiO 2-Pt-3.0 (0.24 mmol h-1 g-1 , 1.88 wt% Pt), and also much higher than those of other TiO 2 nanostructures with the same Pt content. Such H 2 evolution rate is the highest reported for photocatalytic H 2 production with such a low Pt content under simulated solar light. Our strategy here suggests that via alkali modifying the photocatalysts, we can not only enhance the H 2 production for solar energy conversion but also significantly decrease the noble metal content for cost saving.
Unique walnut-shaped porous MnO2/carbon nanospheres via in situ carbonization of amorphous MnO2 nanospheres demonstrate enhanced reaction kinetics for lithium storage.
Hierarchically structured porous TiO2-B spheres have been synthesized via a hydrothermal process using amorphous titania/oleylamine composites as a self-sacrificing template. The TiO2-B spheres are constructed by interconnected nanotubes and possess a high specific surface area of 295 m2 g-1. When evaluated as an anode material in lithium-half cells, the as-obtained TiO2-B material exhibits high and reversible lithium storage capacity of 270 mA h g-1 at 1 C (340 mA g-1), excellent rate capability of 221 mA h g-1 at 10 C, and long cycle life with over 70% capacity retention after 1000 cycles at 10 C. The superior electrochemical performance of TiO2-B material strongly correlates to the synergetic superiorities with a combination of TiO2-B polymorph, hierarchically porous structure, interconnected nanotubes and spherical morphology. Post-mortem structural analyses reveal some discrete cubic LiTiO2 nanodots formed on the outer surfaces of TiO2-B nanotubes, which might account for the slight capacity loss upon prolonged electrochemical cycling.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.