Mesoporous Cu-TiO2-SiO2 Photocatalyst Particles for CO2 Reduction via a Template-free Aerosol Process

WEI-NING WANG, Jinho Park, and Pratim Biswas

Washington University in St. Louis

     Abstract Number: 576
     Last modified: May 13, 2010

Abstract
There is a growing need to mitigate carbon dioxide (CO$_2) emissions, which is one of the major contributors to global climate change. Effective CO$_2 capture can be realized in pre-, post-, or oxy-fuel combustion methods. These processes, however, are energy-intensive and high-cost. The recent innovations have made the photocatalytic technology a potentially promising alternative. The process can be applied for CO$_2 removal while simultaneously converting CO$_2 to carbon-contained energy bearing compounds, such as carbon monoxide, methane, and ethanol. Another potential feature is that it can consume less energy in comparison to conventional methods by harnessing solar energy, which is abundant, cheap, and ecologically clean and safe.
Nanocolloidal silica supported copper doped titania (Cu-TiO$_2-SiO$_2) mesoporous particles were directly synthesized by a template-free furnace aerosol reactor (FuAR). Aqueous suspensions of nanosized TiO$_2 and SiO$_2 colloids and copper nitrate solution were used as precursors. The size, crystallinity, bandgap, and surface area/pore size of the particles properties were tailored by manipulating the precursor concentration, stoichiometric ratio, and temperature, which were characterized by means of SEM, TEM, XRD, UV-VIS, and nitrogen physisorption measurements. CO$_2 reduction was conducted inside a home-made quartz reactor under illumination of UV light followed by GC analysis. The results revealed that the particles were submicrometer-sized mesoporous spheres with average pore sizes from 20 to 30 nm, having optimal molar percentages of TiO$_2 and Cu to the whole particle of 2% and 0.01%, respectively, at which a high CO$_2 conversion efficiency, i.e. CO yield of approximately 20 micromol/g-TiO$_2/hr was achieved. It should be noted that these mesoporous catalyst particles were obtained without using any templates, which avoids contamination and reduces cost.