High Surface Area Mesoporous Oxides Research Articles

Templated Nanocrystal-Based Porous TiO2 Films for Next-Generation Electrochemical Capacitors

The advantages in using nanoscale materials for electrochemical energy storage are generally attributed to short diffusion path lengths for both electronic and lithium ion transport. Here, we consider another contribution, namely the charge storage from faradaic processes occurring at the surface, referred to as pseudocapacitive effect. This paper describes the synthesis and pseudocapacitive characteristics of block copolymer templated anatase TiO(2) thin films synthesized using either sol-gel reagents or preformed nanocrystals as building blocks. Both materials are highly crystalline and have large surface areas; however, the structure of the porosity is not identical. The different titania systems are characterized by a combination of small- and wide-angle X-ray diffraction/scattering, combined with SEM imaging and physisorption measurements. Following our previously reported approach, we are able to use the voltammetric sweep rate dependence to determine quantitatively the capacitive contribution to the current response. Considerable enhancement of the electrochemical properties results when the films are both made from nanocrystals and mesoporous. Such materials show high levels of capacitive charge storage and high insertion capacities. By contrast, when mesoscale porosity is created in a material with dense walls (rather than porous walls derived from the aggregation of nanocrystals), insertion capacities comparable to templated nanocrystal films can be achieved, but the capacitance is much lower. The results presented here illustrate the importance of pseudocapacitive behavior that develops in high surface area mesoporous oxide films. Such systems provide a new class of pseudocapacitive materials, which offer increased charge storage without compromising charge storage kinetics.

Fabrication of two- and three-dimensional model catalyst systems with monodispersed platinum nanoparticles as active metal building blocks

Well-defined Pt monodispersed nanoparticles within the catalytically relevant 1–10 nm size regime were synthesized in solution phase by several synthetic methods which differed in the choice of reducing agent, surface stabilizer, reaction temperature and solvent. Three-dimensional model catalysts were fabricated by incorporating the metal nanoparticles into ordered channels of high surface area mesoporous oxides such as SiO 2, Al 2O 3 and Ta 2O 5 through either sonication or direct synthesis of the oxide support around the particles. Deposition of the same nanocrystals onto silica supports by means of the Langmuir–Schaeffer technique produced two-dimensional model catalysts.

Preparation of a mesoporous high surface area titanium oxo phosphate via a non-ionic surfactant route

Abstract Since the development of the first mesoporous silica materials by scientists of Mobil Oil [J.S. Beck, US Patent (Mobil Oil Corporation) 5, 057 (1991) 296], the synthesis principle has been applied to other metal oxides. Here, we report a new mesoporous titanium oxo phosphate, which is synthesized by a non-ionic template route (N 0 I 0 ). The formation of the mesoporous structure is dominated by hydrogen bonding between self-assembled surfactant micelles and inorganic precursors. A low-cost industrial polyethylenoxide named Dodecanol +5 EO (BASF) was used as a non-ionic surfactant. The N 2 -adsorption isotherm reveals the existence of mesoporosity in these titanium oxo phosphates with a type IV isotherm and a BET-surface area of 350 m 2 g −1 , with pore sizes calculated to be approximately 4.5 nm. The materials are thermally stable up to 550°C, among the highest temperatures reported for very high surface area mesoporous oxides so far.