Development of Nano-Porous Alumina Catalyst Support by Anodic Oxidation of Thermally and Kinetically Sprayed Aluminum Coatings

Abstract

Abstract In order to minimize environmental burden, green technologies should be important in the 21st century. High-performance catalyst layer would make significant contribution through reforming of hydrocarbon fuels, removal of toxic molecules such as CO and NH3 from exhaust gas, reduction of nitrogen oxide (NOx) formation in combustion, and efficient conversion of chemical energy to thermal energy in small scales. Among various kinds of catalyst support, nano-porous alumina (Al2O3) developed with anodic oxidation of aluminum (Al) layers attracts much attention due to its extremely-large specific area, easy controllability of porosity and coating thickness, and large bond strength with the substrate. In our previous studies, we have developed a micro-scale catalytic combustor with a palladium (Pd) /nano-porous Al2O3 catalyst layer, aiming at micro thermophotovoltaic power generation system, which could realize higher energy density than Li-ion batteries. In this paper, we use kinetic- and plasma-spraying for the deposition of Al, and examine the effect of the Al deposition methods on the nano-pore density. It is found that a large number of dislocations in the kinetically sprayed Al particle provide much higher nano-pore density by anodic oxidation. It is also found that nano-porous Al2O3 layer kinetically sprayed and anodized has better characteristics as the catalyst support.