Credit: Oak Ridge National Laboratory
Red and blue represent positions of copper and aluminum atoms, respectively, for two zeolite catalysts (Cu-SSZ-13 and Cu-ZSM-5) used in diesel-vehicle catalytic converters. The catalysts are fresh (that is, not exposed to diesel engine exhaust) or aged (simulated exposure to 135,000 miles of diesel engine exhaust). After long-term aging, the Cu-SSZ-13 catalyst still cleans exhaust while Cu-ZSM-5 does not perform as well. Atom-by-atom 3-D image reconstructions reveal that the degradation of Cu-ZSM-5 is due to severe aggregation of copper and aluminum to form a deleterious phase, CuAl2O4.