Understanding properties of engineered catalyst supports using contact angle measurements and X-Ray reflectivity

Understanding properties of engineered catalyst supports using contact angle measurements and X-Ray reflectivity

Type	Journal Article
Author	Placidus B. Amama
Author	Ahmad E. Islam
URL	http://pubs.rsc.org/en/content/articlelanding/2016/nr/c5nr08108d
Volume	8
Issue	5
Pages	2927-2936
Date	2016/01/29
Abstract	Due to the interest in broadening the type of catalyst substrates that support the growth of high-quality carbon nanotube (CNT) carpets, researchers explored the use of ion beam bombardment to modify catalyst substrates for CNT carpet growth. Employing a combination of contact angle measurements (CAMs) and X-ray reflectivity (XRR), new correlations between the physicochemical properties of pristine and engineered catalyst substrates and CNT growth behavior were established. The engineered surfaces obtained after exposure to different degrees of ion beam damage have distinct physicochemical properties. The CAM data were analyzed using the van Oss–Chaudhury–Good model, enabling the determination of the acid–base properties of the substrate surfaces. For the XRR data, a Fourier analysis of the interference patterns enabled extraction of layer thickness, while the atomic density and interfacial roughness were extracted by analyzing the amplitude of the interference oscillations. The dramatic transformation of the substrate from “inactive” to “active” is attributed to a combined effect of substrate porosity or damage depth and Lewis basicity. Results reveal that the efficiency of catalyst substrates can be further improved by increasing the substrate basicity, if the minimum surface porosity is established. The study advances the use of a non-thermochemical approach for catalyst substrate engineering, as well as demonstrating the combined utility of CAM and XRR as a powerful, nondestructive, and reliable tool for rational catalyst design.