(475c) Metal Oxides As Protective Layers on Carbons and Electrocatalyst Supports

Carbon has long been used as an electrode material in electrochemical processes because it is electrically conductive and easily available at a cheap price. Unfortunately, carbon is not thermodynamically stable in aqueous systems due to its low oxidation potential. Electrochemical corrosion of carbon can be a serious problem in many kinetically accelerated processes, for example, in low temperature fuel cells, rechargeable batteries, and supercapacitors. It has become a great challenge to discover new materials, both electrically conductive and chemically resistant to corrosion, to replace carbon.

In this talk, a brief review of metal oxides as electrocatalyst support will be given first, focused especially on fundamental electrochemical aspects in oxygen reduction reaction (ORR). Following that I will present our studies on preparing high surface area metal oxides in the form of nanoscale particles and nanocoatings on, for example, carbons. We have developed techniques to make titania and niobia nanocoatings on different carbons, including carbon black and carbon nanotubes. To make the oxides electrically conductive, carbon activation and elemental doping were used and found to be effective. Carbon activation was also found to lower phase transformation temperatures, making it possible to transform the metal oxides to the right phase without sintering and thus retaining the nanoscale morphology of the coatings. When Pt catalyst nanoparticles were deposited on the oxides, they were more uniformly dispersed and stabilized due to metal-support interactions. The Pt catalysts also showed better activity.