Gold on Different Manganese Oxides: Ultra-Low-Temperature CO Oxidation over Colloidal Gold Supported on Bulk-MnO2 Nanomaterials

Nanoscopic gold particles have gained very high interest because of their promising catalytic activity for various chemicals reactions. Among these reactions, low-temperature CO oxidation is the most extensively studied one due to its practical relevance in environmental applications and the fundamental problems associated with its very high activity at low temperatures. Gold nanoparticles supported on manganese oxide belong to the most active gold catalysts for CO oxidation. Among a variety of manganese oxides, Mn2O3 is considered to be the most favorable support for gold nanopartides with respect to catalytic activity. Gold on MinO(2) has been shown to be significantly less active than gold on Mn2O3 in previous work. In contrast to these previous studies, in a comprehensive study of gold nanopartides on different manganese oxides, we developed a gold catalyst on MnO2 nanostructures with extremely high activity. Nanosized gold particles (2-3 nm) were supported on alpha-MnO2, nanowires and mesoporous beta-MnO2 nanowire arrays. The materials were extremely active at very low temperature (-80 degrees C) and also highly stable at 25 degrees C (70 h) under normal conditions for CO oxidation. The specific reaction rate of 2.8 mol(CO).h(-1).g(Au)(-1) at a temperature as low as -85 degrees C is almost 30 times higher than that of the most active Au/Mn2O3 catalyst.