Structural Characteristics of Fresh, Thermally Aged, Poisoned and Regenerated Pt-Pd Catalysts Studied by Analytical Transmission Electron Microscopy

Transportation is one of the largest emission sources of air pollution. To reduce emissions and to meet emission legislation, efficient exhaust gas purification systems in vehicles are needed. PtPd/Al2O3 based catalysts are commonly used in such purification system in combustion engines. Catalyst deac-tivation caused by thermal aging and poisoning is a significant challenge and strong efforts to further develop durable catalysts are required. Thermal aging is the loss of active surface area due to sintering of the active phase or the support material. Poisoning is due to the adsorption of impurities on the cata-lytically active sites [1]. The highest concentration of contaminants found in the catalysts are typically sulfur and phosphorus originating from engine oil, lubricants, and/or fuels [2]. The reactivation of a sulfur-poisoned catalysts at elevated temperatures is a very important research topic to extend the cata-lyst lifetime. Here, we present case studies to show that analytical (scanning) transmission electron mi-croscopy, (S)TEM, is a very useful characterization tool, combined of course with other techniques, to study aging and regeneration phenomena in catalysts.