Yu-Cheng Liu

Reduction mechanism of iron titanium based oxygen carriers with H2 for chemical looping applications – a combined experimental and theoretical study

The reduction mechanisms of three iron titanium based oxygen carriers with H2 have been investigated by experimental and theoretical methods for the chemical looping process. The oxygen carriers have been successfully prepared and the initial rate for the reduction reactions has been predicted as a function of initial molar concentration of Fe2TiO5, Fe2TiO4 and FeTiO3 at different temperatures from 800 to 1000 °C. Density functional theory calculations have been used to explain the reduction mechanism of oxygen carriers with H2. Our results show that the reduction of Fe2TiO5 with H2 has the smallest activation energy compared with the others. The observed rate constant values indicate that the reduction mechanism of Fe2TiO5 is much faster than that of the others. Also, we found that the diffusion of a H atom from Fe is the rate determining step for the reduction of the three iron titanium oxygen carriers. Additionally, the experimentally predicted activation energies are in good agreement with the theoretical values.

Fabrication of TiO2 nanotube arrays of different dimension for photocatalytic decomposition of IPA in air streams

Abstract TiO2 nanotube arrays (TNTs) were fabricated by anodization under various operational conditions. Dimensions of fabricated TNTs were significantly influenced by the temperature and water content of ethylene glycol-based electrolyte prepared for anodization. TNTs of longer length, larger inner diameter, and thinner wall thickness were fabricated in electrolytes of higher temperatures. For TNTs fabricated in electrolyte containing higher water contents, the relatively fast dissolution of TiO2 led to the formation of TNTs of shorter tube length and larger inner diameter. TNTs were fabricated under different anodization conditions (mainly the water content in ethylene glycol electrolyte and anodization time) to exhibit similar tube length and different inner diameters. Experiments conducted using TNTs of longer tube lengths and smaller inner diameters demonstrated higher photocatalytic decompositions of gaseous isopropyl alcohol (IPA); however, the photocatalytic application of TNTs is limited by the penetration of illumination.